ReducingSugarProductionfrom Teff StrawBiomassUsingDilute ...

Research ArticleReducing Sugar Production fromTeff StrawBiomassUsingDiluteSulfuric Acid Hydrolysis Characterization and OptimizationUsing Response Surface Methodology

Andinet Alemayehu Tesfaw and Belachew Zegale Tizazu

Department of Chemical Engineering Addis Ababa Science and Technology University Addis Ababa Ethiopia

Correspondence should be addressed to Belachew Zegale Tizazu belachewzegaleaastueduet

Received 13 August 2021 Revised 20 September 2021 Accepted 19 October 2021 Published 2 November 2021

Academic Editor Wen-Cheng Chen

Copyright copy 2021 Andinet Alemayehu Tesfaw and Belachew Zegale Tizazu is is an open access article distributed under theCreative CommonsAttribution License which permits unrestricted use distribution and reproduction in anymedium providedthe original work is properly cited

e present study evaluated first the characterization of Teff straw and then BoxndashBehnken design (BBD) and response surfacemethodology was adopted to optimize the parameters (hydrolysis temperature dilute sulfuric acid concentration solid to liquidratio and hydrolysis time) of dilute sulfuric acid hydrolysis of Teff straw in order to get a maximum yield of total reducing sugar(TRS)e chemical analysis of Teff straw revealed high amounts of cellulose (418 wt) hemicellulose (38wt) and lignin (17wt) e morphological analysis using SEM showed that hydrolyzed Teff straw with dilute sulfuric acid has more pores anddistorted bundles than those of raw Teff straw XRD analysis also indicated that hydrolyzed Teff straw has higher crystallinity indexand smaller crystallite size than raw Teff straw which might be due to removal of hemicellulose amorphous cellulose and lignincomponents Under the optimized conditions for dilute sulfuric acid hydrolysis of Teff straw (120degC 4 vv H2SO4 concentration1 20 solid to liquid ratio and 55min hydrolysis time) we have found a total reducing sugar yield of 2665mgg e results ofvalidation experiment under the optimum conditions agreed well with model predictions

1 Introduction

Biomass is by far the largest energy provider contributing atotal of 1150 million tons of oil equivalent which translatesinto a 79 share of the total energy supply [1] Because of thedepletion of fossil fuels and environmental pollution re-searchers have been committed to studying the productionof value-added chemicals and biofuels originated fromlignocellulosic biomass [1] Lignocellulosic biomass is anabundant and inexpensive source of fermentable sugars forthe production of biofuels and value-added chemicals Teffstraw is among the lignocellulosic materials used for thesynthesis of biofuels and value-added products [2] Likeother lignocellulosic materials the main components of Teffstraw are cellulose hemicellulose and lignin Teff straw hasnot been studied much for its potential applications Dame[2] reported that in Ethiopia an average of 37 million tons ofTeff cereal has been produced per annum correspondingly

large amount of Teff straw has been produced duringbanging which was more than 2 million tons of Teff straw inevery year It has been primarily disposed of throughburning in the field rather than used as animal feed edisposed of Teff straw could cause environmental pollutionus converting to valuable products such as total reducingsugar for subsequent conversion of value-added chemicalsand biofuels is a preeminent option instead of burning themand disposing of them to the environment

Lignocellulosic biomass typically consists of (1) cellulose(30ndash50) a polymer of β-linked D-glucose which issusceptible to enzymatic hydrolysis and easy to metabolize(2) hemicellulose (15ndash40) primarily C5 and C6 sugars(3) lignin (15ndash35) which is difficult to metabolize and isa randomly cross-linked aromatic polymer of phenyl pro-pane units combined by different linkages (CndashOndashC ethersand CndashC) resisting biochemical conversion and demandinghigh temperatures to convert and (4) other components

HindawiInternational Journal of BiomaterialsVolume 2021 Article ID 2857764 13 pageshttpsdoiorg10115520212857764

such as extractives and ash Due to its heterogeneouscomposition hemicellulose is of particular interest toresearchers ie hemicellulose is branched heteropolymerswith a degree of polymerization of around 80 to 200 and isdepolymerized into its monomeric units mainly xyloseand their subsequent conversion into biofuels and value-added products via microbial fermentation [3] Pretreat-ment is the crucial stage in the transformation of ligno-cellulosic biomass to fermentable sugars It is vital to alterthe structure of cellulosic biomass for hydrolysis is isdue to the crystallinity of cellulose degree of polymeri-zation moisture content available surface area and lignincontent [4] Pretreatment has been recognized as one ofthe most expensive processing steps in lignocellulosicbiomassndashtondashfermentable sugars conversion e goals ofany pretreatment are (1) the increase of the surface areaand porosity (2) modification of lignin structure andremoval of lignin (3) depolymerization of hemicelluloseand removal of hemicellulose and (4) reduction of thecrystallinity of cellulose An effective pretreatment should(1) avoid the need for reducing the size of biomass particle(2) preserve the pentose (hemicellulose) fractions (3) limitthe formation of degradation products that inhibit thegrowth of fermentative microorganism and (4) minimizeenergy demands in addition the pretreatment agentshould have low cost and be capable of recycling inex-pensively [5] Pretreatment with concentrated acids suchas hydrochloric acid and sulfuric acid can result in en-hancement of enzymatic hydrolysis of lignocellulosicbiomass to produce fermentable sugars Even though theyare strong agents for cellulose hydrolysis concentratedacids are toxic corrosive and hazardous and thus requirereactors that are resistant to corrosion which makes thepretreatment process very expensive In addition theconcentrated acid must be recovered after hydrolysis tomake the process economically feasible [6 7] Dilute acidhydrolysis has been widely used for pretreatment of lig-nocellulosic biomass is is due to high hydrolysis ratebeing specific toward hemicellulose and being moreeconomical than enzymatic concentrated acid and basepretreatment [8] e yield of fermentable sugars duringacid hydrolysis is affected by various factors such as hy-drolysis time solid to liquid ratio hydrolysis temperatureand acid concentration Dilute sulfuric acid hydrolysis isthe most common and effective pretreatment process forTeff straw [9] but other reagents such as hydrochloricnitric and phosphoric acids can also be used Variousresearch works have been done on optimization of diluteacid hydrolysis of different lignocellulosic biomass usingresponse surface methodology Limited reports have beenobtained on the optimization of dilute acid hydrolysis ofTeff straw to produce total fermentable sugars using re-sponse surface methodology e conventional method ofoptimization involves varying one factor at a time andkeeping the others constant It might be useful but does notexplain the effects of interaction between the variousfactors under consideration us the response surface

methodology which is a collection of mathematical andstatistical techniques for empirical modeling was used foroptimization of dilute sulfuric acid hydrolysis of Teff strawfor total reducing sugar production e present studyaimed to statistically optimize the process parameters (vizsulfuric acid concentration or load hydrolysis tempera-ture hydrolysis time and solid to liquid ratio) of dilutesulfuric acid hydrolysis of Teff straw Prior to responsesurface methodology followed by BoxndashBehnken design(BBD) optimization of dilute sulfuric acid hydrolysis ofTeff straw the composition of Teff straw was first analyzedBoxndashBehnken design (BBD) has been used to design andoptimize the process parameters of dilute sulfuric acidhydrolysis conditions and the interaction among theseparameters on dilute acid hydrolysis of Teff straw to obtainmaximum total reducing sugars yield

2 Materials and Methods

21 Materials and Chemicals Teff straw was collected fromDebre Zeyit Oromia Region Ethiopia as the raw materialfor total reducing sugar production All chemicals and re-agents used throughout this study were of analytical reagent(AR) grade and maximum purity from HiMedia and Ran-chem India e reagents were obtained from AtomicEducational Materials Supply PLC Sulfuric acid hydro-chloric acid and methylene blue indicator (purity 98 37and 100 respectively) were obtained from Blulux Labo-ratories Pvt Ltd In addition potassium hydroxide (9808pure HiMedia Laboratories Pvt Ltd) was required to de-termine the total reducing sugar by Fehling solutionmethodSodium hydroxide (9808 pure HiMedia Laboratories PvtLtd) was employed for determination of hemicellulosecontent of Teff straw whereas sulfuric acid H2SO4 (LOBAChemie purity 98) was used to determine the lignincontent

22 Collection and Preparation of Teff Straw Teff strawcollected from Debre Zeyit Oromia Region Ethiopia waswashed three times in order to remove soluble componentsand dust particles It was then sun-dried for two days for thenext size reduction process e dried Teff straw was groundand screened using a standard sieve for the average particlesize of 710 μm (071mm) e particle size was taken basedon the previous literature reported elsewheree sieved Teffstraw was stored in a zipped lock plastic bag at ambienttemperature until use

23 ProximateAnalysis of Teff Straw e proximate analysisof Teff straw viz moisture content total ash content totalvolatile matter and fixed carbon was determined usingstandard procedures of gravimetric methods

231 Determination of Moisture Content is was done bythe gravimetric method About 15 gram of finely pow-dered Teff straw was weighed into the silica crucible then

2 International Journal of Biomaterials

the crucible was placed without lid in electric hot air ovenby maintaining a temperature of 105degC for an hour toevaporate water and the crucible was then taken outcooled in desiccator and weighed for loss in weighterefore weight of Teff straw sample before and afterheating (weight of Teff straw sample + weight ofcrucible) minus weight of crucible [10]

MC() g minus x

g1113888 1113889 times 100 (1)

where g is the weight of sample x is the weight of dry matterand (g minus x) is the loss in weight

232 Determination of Ash Content is was done by thefurnace incineration gravimetric method 30 g of the pro-cessed Teff straw was measured into a previously weighedporcelain crucible Finley powdered Teff straw in the cru-cible was heated without lid in a muffle furnace at a tem-perature of 700degC for 20 minute Afterward the crucible wastaken out cooled first in open air then transferred todesiccator and weighed Accordingly weight of cruci-ble +weight of Teff straw before heating was given as weightof crucible +weight of Teff straw after heating Finallyweight of ash (weight of sample +weight of crucible) minus

weight of crucible

Ash() w1 minus w2

w1times 100 (2)

where W1 is the initial weight of sample before burning andW2 is the final weight of sample after burning

233 Total Volatile Matter Total volatile matter is theweight loss obtained on heating e Teff straw in thecrucible was covered with a lid placed in muffle furnace andmaintained at a temperature of 900degC for 9 minutes to avoidtoxic matters After 9 minutes the crucible was cooled in airafterward it was kept into desiccator and weighed ere-fore weight of Teff straw before heating could be totalweight minus weight of crucible at the same time weight of Teffstraw after heating (weight of sample +weight of crucible)weight of crucible Finally total weight loss of moisture Teffstrawweight loss due to volatile matter +moisture Weightloss due to volatile matter total weight loss minus moisture

VM() weight loss due to volatilematter

weight of Teff straw1113888 1113889 times 100

(3)

234 Fixed Carbon e FC of Teff straw can be determinedas in the following equation

FC() 100 minus (VM + Ash + MC) (4)

where VM is the volatile matter and MC is the moisturecontent

24 Chemical Composition Analysis of the Teff Straw

241 Determination of Extractives e amount of extrac-tives in Teff straw was estimated by using Soxhlet extractionapparatus through extraction thimbles Acetone 400mL for3 g of oven-dried Teff straw was used as the solvent forextraction and the temperature was held at 70degC for a 4 hrun period on the heating mantle e sample was air-driedfor few minutes at room temperature It was then dried at105degC in an oven until a constant weight was obtained andthen cooled in a desiccator [11 12] e percent by weight ofthe extractives content was evaluated as the difference inweight between the raw extractive-laden Teff straw andextractive-free Teff straw

242 Determination of Hemicellulose 2 g of extracted driedTeff straw was transferred to a 250mL Erlenmeyer flask150mL of 05M sodium hydroxide was added e mixturewas boiled for 35 h with distilled water so as to increase theheating effect and minimize lime scales that can come fromtap water It was filtered after cooling through vacuumfiltration and washed until neutral pHe residue was driedto a constant weight at 105degC in an oven e differencebetween the sample weight before and after this treatmentwas the hemicellulose content (wt) of oven-dried Teff straw[13 14]

243 Determination of Lignin 305 g of dried extracted Teffstraw was weighed in glass test tubes and 30mL of 72 wt ()H2SO4 was addede sample was kept at room temperaturefor 2 h with careful shaking at 30min intervals to allow forcomplete hydrolysis After the initial hydrolysis 84mL ofdistilled water was added in order to get 4 wt () H2SO4solutions e second step of hydrolysis was made in anautoclave for 1 h at 121degC e mixture was then cooled atroom temperature Teff straw hydrolysate was filteredthrough vacuum filtration e acid insoluble lignin wasdetermined by drying the residues at 105degC and cooled in adesiccator e acid soluble lignin fraction was determinedby measuring the absorbance of the acid hydrolyzed samplesat 278 nm e lignin content (wt) was determined as thesummation of acid insoluble lignin and acid soluble lignin[14]

244 Determination of Cellulose e cellulose content (ww) was determined by difference assuming that extrac-tives hemicellulose lignin and cellulose are the onlycomponents of the entire biomass

25AcidHydrolysis for theProduction ofTotalReducing Sugar

251 Estimation of Total Reducing Sugar by FehlingMethodsDetermination of total reducing sugars was based on theprocedures of Lane and Eynonrsquos method To determine thetotal reducing sugars two separate Fehling solutions wereprepared and labeled as Fehlingrsquos A and Fehlingrsquos Be twosolutions were mixed in equal volumes to get the final

International Journal of Biomaterials 3

Fehlingrsquos solution which has a deep blue color [15] De-termination of Fehling factor was the first step for thismethod in which 5ml of each solution Fehlingrsquos A and Bwas taken out 1732 g of copper sulfate was dissolved in250ml of distilled water in the volumetric flask to prepareFehling A whereas Fehling B was prepared by using 865 g ofRochelle salt (potassium sodium tartrate) and 25 g of sodiumhydroxide dissolved in 250ml of distilled water in thevolumetric flask A 1 g of methyl blue indicator and 1 g of dyephenolphthalein indicator were mixed with distilled water tomake up a volume of up to 100ml and dissolved in ethanol tomake up a volume of 100ml for Fehling factor determi-nation [15]

252 Standardization of the Fehlingrsquos Solution for InvertSugars For standardization of the Fehlingrsquos solution forinvert sugars 475 g of analytical grade sucrose was dissolvedwith 50ml distilled water in 500ml volumetric flask and at atime 5ml concentration HCl was added and allowed to standfor 24 hrs Subsequently this solution was neutralized withsodium hydroxide using phenolphthalein as endpoint in-dicator After uniform mixing 25ml of the solution wastransferred to a 100ml volumetric flask making up tovolume (ie 1ml 25mg of invert sugar) by transferring tothe burette having an off-set tip and titrated against Feh-lingrsquos solution as described in the following equation

Factor for Fehlingrsquos solution(g of invert suger) 00025 times V1(ml)

(5)

Preliminary titration 5ml of each solution Fehling Aand B was pipetted into 250ml conical flask e solutionwas then mixed uniformly and added to 10ml water and fewpumice stone or glass beads e sugar solution was dis-pensed from the burette and then heated to boiling reedrops of methylene blue indicator were added dropwise tothe sugar solution until the blue color disappears to a brickred endpoint

Final titration 5ml of each solution Fehling A and Bwas pipetted into a 250ml conical flask 005 to 10ml samplesolution from titer value of the preliminary titration wasadded to the flask and heated to boiling Subsequently 3drops of methylene blue indicator were added e titrationwas completed within 1min by adding 2 to 3 drops of sugarsolution at a time until the indicator was decolorized Fi-nally we noted down the titer value when the boiling liquidwas changed to brick red color e volume of clarifiedsample solution required for Fehlingrsquos reaction (titer) wasrepresented as V3 (ml) Based on the factor for Fehlingrsquossolution V3 (ml) sample solution contained 00025 V3 greducing sugar (as invert sugar) To determine the totalreducing sugars of Teff straw 50ml of the hydrolysate fromTeff straw was pipetted into a 100ml volumetric flask en5ml of concentrated hydrochloric acid was added andallowed to stand at room temperature for 24 hrs and thenthe solution was neutralized with concentrated sodiumhydroxide solution of 01N using phenolphthalein as end-point indicator e titration was performed against Feh-lingrsquos solution the total reducing sugars were determined as

invert sugars and the solution was transferred to 50mlburette having an off-set tip which was represented astiterV4 (ml) Based on the factor for Fehlingrsquos solutiontotal reducing sugars in V4 (ml) 00025timesV1 g 50ml of theclarified and deleaded solution was diluted twice (50ml to100ml) after hydrolysis Dilution volume of the hydrolyzedTeff straw would be 2timesV2 according to the procedure of[16] e total reducing sugar (as invert sugar ) was de-termined as in the following equation

total reducing sugar(as invert sugar) 05 times V1 times V2

V4 times W

(6)

where 05timesV1 is the Fehling factor (g)V2 is the volumerequired for hydrolysis (ml)V4 is the titer (ml) andW is theweight of the Teff straw used in hydrolysis (g)

26 Scanning Electron Microscope (SEM) Analysis emodification of surface structure of Teff straw was analyzedby SEM [16ndash20] SEM analysis has been employed mostdominantly in order to determine themicrostructure of bothraw and acid hydrolyzed Teff straw

27 X-Ray Diffraction (XRD) Analysis e effect of thecrystal size on the X-ray patterns has been studied indetail by using the origin software is software con-siders the peak shape analysis to provide information oncrystal size and percentage of crystallinity of samples onthe other hand a powder diffraction file is required forthe analysis of the effect of the crystal size on the X-raydiffraction pattern In order to analyze the crystallinestructure of this Teff straw X-ray diffractometer equip-ped with copper (Cu) radiant source energy of 40 kVelectric current of 30 mA scanning speed of 3omin andscanning range of 10 to 80 degrees was used Crystallinity(peak to noise ratio) can be determined using the fol-lowing equation

crystallinity area of crystalline peaks

area of all peaks(crystalline + amorphous)times 100

(7)

From XRD data area of crystalline peaks and area of allpeaks of untreated and treated Teff straw respectively couldbe found using OriginPro and Excel software In XRD datathe broadening (βT) of peaks is due to the combined effect ofcrystallites size (βD) and macrostrain (βε) that can beexpressed as the following equation

βT βD + βε (8)

where βT is the total broadening βD is broadening due to thecrystallite size and βε is the broadening due to strain Fromthe Scherrer equation the crystallite size was adopted in theequation below

D Kλ

βD cos θ (9)


where βD is the FWHM (broadening of the peak) inradians K is the shape factor (094) λ is the wavelength ofX-ray source (015406 nm) and θ is the position of the peakin radians Similarly the XRD peak broadening due tomicrostrain is given by the following equation

βε 4ε tan θ (10)

where βε is broadening due to strain and ε is strainSubstituting (9) and (10) into (8) we get the followingequation

βT cos θ ε(4 sin θ) +KλD

(11)

Equation (11) represents a straight line in which ε is theratio between two lengths (slope) of the line (dimensionlessquantity) and KλD is the y-intercept by calculating FWHMand peak position from XRD data From the data of W-Hplot y-intercept is (KλD) and slope (ε) is strain

28 Experimental Design Four-variable (temperatureconcentration of H2SO4 solid to liquid ratio and hydrolysistime) BoxndashBehnken design (BBD) with three replicates atthe center point was performed to optimize the parametersof dilute sulfuric acid hydrolysis conditions for maximumtotal reducing sugar (TRS) yield from Teff straw e ex-perimental design consisted of 27 runs including threecenter pointse experimental data for total reducing sugar(TRS) yield from Teff straw was fitted using a second orderpolynomial function model

Y βo + 1113944 βiXi + 1113944 βiiX2i + 1113944 βijXij (12)

where Y is the response βo a constant βi the linear coef-ficients βii the squared coefficients and βij the interactioncoefficients

Coded and actual value levels of the variables forBoxndashBehnken design are shown in Table 1 e design andlevels of variables with experimental total reducing sugar(TRS) yield from the dilute sulfuric acid hydrolysis of Teffstraw are given in Table 2 Design-Expert statistical software7 (trial version) was used for the analysis and optimization ofthe experimental data Analysis of variance (ANOVA) wasperformed in order to evaluate the statistical significance ofthe model

3 Results and Discussion

31 Proximate Analysis Table 3 depicts the proximateanalysis of Teff straw as compared to other biomass sourcese proximate values determined in the present study weremoisture content 67 volatile matter content 785fixed carbon 23 and ash content 125 As shown inTable 3 the values of proximate analysis determined in thisstudy are comparable to the previous studies

32 Determination of Chemical Composition of Teff Strawe chemical composition of Teff straw (viz cellulosehemicellulose lignin and extractive contents) was

determined using standard gravimetric procedure Table 4shows the chemical composition of Teff straw as compared toother various biomass sourcese compositional analysis ofTeff straw for the present study was as followscellulose 418 wt hemicellulose 380wtlignin 170wt and extractive content 32 wt on drybasis e results of this study are comparable to otherbiomass sources e chemical compositional analysis re-sults revealed that Teff straw biomass shows promisingsources for biofuels and value-added chemicals productiondue high contents of cellulose hemicellulose and lignin Teffstraw having a cellulose content of 418 and hemicellulosecontent of 38 indicates promising source of total reducingsugarTeff straw has almost comparable amount of lignincontent to that of other feedstocks in particular it has al-most the same amount of lignin as wheat straw but highercellulose which could be sustained at higher temperatureduring hydrolysis

33 SEM Analysis of Raw and Acid Hydrolyzed Teff StrawFigures 1(a) and 1(b) show the morphological features ofraw and acid hydrolyzed Teff straw Figure 1(a) showsregular and compact surface structure with fibersarranged in bundles in Teff straw e surface morphologyof the acid hydrolyzed Teff straw changed as compared toraw Teff straw Dilute sulfuric acid pretreatment coulddestroy the cellulose-hemicellulose-lignin structurethereby removing some of the external fibers us thelignin and hemicellulose of the dilute H2SO4 acid pre-treated Teff straw were partially removed and broken orbecame loose e exposure of internal structures of Teffstraw with acid increases the accessibility of cellulose forfurther processing [10] e results of SEM analysis(Figure 1(b)) indicated that acid hydrolysis of Teff strawshowed significant surface modification ie developedhoneycomb-like rough surfaces nonuniform pores andcavities caused by the reaction between H2SO4 and esterbonds which led to removal of lignin and hemicellulosewith cellulose domination [7]

34 XRD Analysis of Raw and Acid Hydrolyzed Teff StrawFigures 2(a) and 2(b) depict XRD patterns of raw and acidhydrolyzed Teff straw e percentage of crystallinity of rawTeff straw was 6412 whereas the percentage of crystallinityof acid hydrolyzed Teff straw was 657044 showed that thepretreated rice straw by dilute acid has higher crystallinitydegree (672) when compared to native rice straw(5937) so the increased crystallinity index after pre-treatment might be due to hydrolysis of glycosidic linkagesin the cellulose accessible regions e percentage of crys-tallinity of acid hydrolyzed Teff straw is higher than that ofthe raw Teff straw due to the removal of hemicellulose andamorphous parts of cellulose in the hydrolysate and due tohydrolysis of glycosidic linkages in the cellulose accessibleregions so the crystallinity of Teff straw is comparable withrice straw In general terms the acid hydrolyzed Teff strawgenerates better-defined signals than the raw one whichshows the elimination of noncrystalline components due to


the effects of pretreatments added to a slight increase in thesignals that denote the crystalline structure of cellulose

35 Effects of Dilute Acid Hydrolysis of Teff StrawFigure 3 depicts the effect of dilute sulfuric acid and hy-drolysis temperature at hydrolysis time of 60min and solidto liquid ratio of 1 20 on the yield of total reducing sugar(TRS) from Teff straw As shown in Figure 3 for all diluteacid concentrations the yield of total reducing sugar (TRS)increased as the hydrolysis temperature increased from 80degto 140degCis is due to the fact that higher temperature leadsto more hydrolysis of the hemicellulose and amorphousportion of the cellulose For hydrolysis temperatures of 100deg120deg and 140degC the yield of total reducing sugar (TRS) fromTeff straw decreased as the acid concentration exceeded 4 vv() is might be due to the degradation of monomericsugars in the total reducing sugar to their degradationproducts especially furfural and 5-hydroxymethyl furfural(5-HMF) e maximum total reducing sugar (TRS) yield of

255mgg was obtained at a temperature of 120degC and acidconcentration of 4 vv () and the minimum total reducingsugar (TRS) yield of 151mgg was obtained at a hydrolysistemperature of 80 and acid concentration of 05 vv () eminimum total reducing sugar (TRS) was obtained at lowertemperature and acid load is is because at lower tem-perature and acid concentration it is hard to extract totalreducing sugar (TRS) from the lignocellulosic biomass

Figure 4 shows the effect of temperature and hydrolysistime on yield of total reducing sugar (TRS) from Teff straw atdilute sulfuric acid concentration of 4 vv () and solid toliquid ratio of 1 20 As depicted in the Figure 4 the yield oftotal reducing sugar (TRS) decreased as the hydrolysistemperature exceeded 120degC for all values of hydrolysis timee maximum total reducing sugar (TRS) yield of 241 and248mgg was obtained at 120degC for 60min and 70minrespectively ese results showed that hydrolysis temper-ature of 120degC and longer hydrolysis time favor the ex-traction of hemicellulose and amorphous portion ofcellulose However for hydrolysis temperatures beyond

Table 1 Coded and actual value levels of the variables for BoxndashBehnken design

Independent variables Symbol Coded and actual value levelsminus 1 0 +1

Acid concentration ( vv) A 05 225 4Hydrolysis temperature (oC) B 80 100 120Hydrolysis time (min) C 30 45 60Liquid to solid ratio (mlg) D 10 20 30

Table 2 Experimental results for the dilute acid hydrolysis of Teff straw for total reducing sugar (TRS) yield

Run No Acid concentration (vv ) Temperature (oC) Hydrolysis time (min) Liquid to solid ratio (mlg) TRS (mgg)1 225 8000 3000 2000 1672 400 10000 4500 1000 2353 225 8000 4500 3000 1814 225 10000 4500 2000 2015 225 12000 6000 2000 2436 050 10000 4500 1000 1647 225 8000 6000 2000 198 225 12000 4500 1000 2289 225 10000 4500 2000 20110 050 10000 4500 3000 17911 225 10000 6000 1000 21512 225 10000 6000 3000 21213 225 10000 3000 3000 19514 050 8000 4500 2000 15915 225 10000 4500 2000 20116 225 12000 4500 3000 22617 225 10000 3000 1000 18718 050 12000 4500 2000 18719 225 8000 4500 1000 16820 400 12000 4500 2000 26321 225 12000 3000 2000 20822 400 10000 3000 2000 21423 050 10000 6000 2000 18524 400 10000 6000 2000 24525 050 10000 3000 2000 16926 400 8000 4500 2000 19627 400 10000 4500 3000 231


120degC and longer time there might be decomposition ofmonomeric sugars to their degradation products For lowertemperature (80degC) the yield of total reducing sugar (TRS)from Teff straw wasminimum for the shorter hydrolysis time(30min and 40min) considered (Figure 4)is is because atlower temperature and shorter hydrolysis time extraction oftotal reducing sugar (TRS) from Teff straw was difficult

Figure 5 depicts the effect of hydrolysis time and dilutesulfuric acid concentration on yield of total reducing sugar(TRS) from Teff straw (hydrolysis temperature 120degC andsolid to liquid ratio 1 20) Figure 5 depicts the maximumtotal reducing sugar (TRS) yield of 212mgg 229mgg242mgg and 252mgg for dilute sulfuric acid concen-tration of 2 vv 3 vv 5 vv and 4 vv () respectively fromTeff straw at hydrolysis time of 60min e more total re-ducing sugar (TRS) yield for 4 vv () sulfuric acid con-centration than 5 vv () sulfuric acid concentration at60min hydrolysis time is essentially due to the degradationof monomeric sugars to their degradation products at higheracid concentration and longer hydrolysis time e yield oftotal reducing sugar (TRS) from Teff straw was minimal forall sulfuric acid concentrations considered in the experi-ments for shorter hydrolysis time (Figure 5)

Figure 6 shows the effect of solid to liquid ratio andhydrolysis temperature on the yield of total reducing sugar

(TRS) from Teff straw (dilute sulfuric acid concentration 4vv () and hydrolysis time 60min) Figure 6 shows slightvariation in the yield of total reducing sugar (TRS) from Teffstraw for specific hydrolysis temperatures (eg at 80degC) asthe solid to liquid ratio varied from 1 10 to 1 30 emaximum total reducing sugar (TRS) yield of 245mgg wasobtained at a solid to liquid ratio of 1 20 and hydrolysistemperature of 120degC from Teff straw Figure 6 indicates thatthe total reducing sugar (TRS) yield (mgg) increased as thesolid to liquid ratio varied from 1 10 to 1 30 is was dueto excess of liquid phase in hydrolysis mixture (solid toliquid ratio of 1 20 and 1 30) which helps in maximumhydrolysis of hemicellulosic and amorphous fraction ofcellulose Large excess of liquid phase also reduces bulkconcentration of monomeric sugars resulting from hydro-lysis which helps in minimizing their further degradation tofurfural and 5-HMF in the reaction mixture

36 Optimization of Dilute Sulfuric Acid Hydrolysis on TRSYield from Teff Straw e second order polynomial modelequation for the fitted data using coded values of inde-pendent variables and total reducing sugar (TRS) yield as aresponse variable is as follows

Total reducing sugar(TRSmgg) +602 minus 144A + 007B minus 0006C + 034 D

+ 003A2

minus 104 times 10minus 4B2

+ 481 times 10minus 4C2

minus 417 times 10minus 5D

2+ 003AB + 002AC

minus 003AD + 100 times 10minus 3BC minus 175 times 10minus 3

minus 183 times 10minus 3CD

(13)

Table 3 Results of proximate analysis of Teff straw as compared to other biomass sources

Biomass sources Moisture () Volatile matter () Ash content () Fixed carbon () ReferencesTeff straw 67 785 125 23 Present studyRice hulls 90 708 111 181 [21]Wheat straw 79 769 40 191 [22]Sugarcane bagasse 45 771 24 160 [23]Rice straw 69 586 200 148 [24]Switch grass 91 731 38 230 [25]Corn cob 117 723 107 49 [24]Water hyacinth 29 671 139 189 [26]

Table 4 Results for chemical composition analysis of Teff straw compared with other biomass sources

Biomass Extractive (wt) Cellulose (wt) Hemicellulose (wt) Lignin (wt) ReferencesTeff straw 32 418 38 17 Present studyWheat straw 3 38 37 17 [22]Sugarcane bagasse 337 4084 3079 25 [8]Rice straw 322 35 243 1773 [27]Switch grasses mdash 45 314 12 [6]Corn cob mdash 4127 46 740 [28]Water hyacinth mdash 3167 2733 393 [29]Pineapple waste 11 30 37 22 [11]Barely straw mdash 14ndash19 27ndash38 31ndash45 [30]


Table 1 depicts the experimental results for the diluteacid hydrolysis of Teff straw for total reducing sugar (TRS)yield e maximum total reducing sugar of 263mgg wasobtained at an experimental run number of 20 temperatureof 120degC acid concentration of 4 vv hydrolysis time of 45

minutes and solid to liquid ratio of 1 20 On the other handthe minimum yield of 159mgg was obtained at an ex-perimental run number of 14 temperature of 80degC acidconcentration of 05 vv solid to liquid ratio of 1 20 andhydrolysis time of 45 minutes e results of maximum and

(a) (b)

Figure 1 SEM analysis of raw (a) and acid hydrolyzed (b) Teff straw

1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

157

622

38

344

837

78

439

6

643

2

774

2

(a)

1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

160

822

16

349

437

74

439

8

643

6

774

6

(b)

Figure 2 XRD analysis of raw (a) and acid hydrolyzed (b) Teff straw

14

16

18

20

22

24

26

TRS

(mg

g)

1 2 3 4 50Acid concentration (vv )

100degC120degC

140degC80degC

Figure 3 e effect of dilute sulfuric acid concentration and hydrolysis temperature on the yield of total reducing sugar (TRS) from Teffstraw (hydrolysis time 60min and solid to liquid ratio 1 20)


minimum yield of total reducing sugar (TRS) reveal that atlower temperature and acid concentration the total re-ducing sugar (TRS) extraction was also lower At highertemperature the increase in the total reducing sugar (TRS)yield might be due to sufficient temperature and acidconcentration to hydrolyzed Teff straw whereas the lowertemperature was not sufficient enough to hydrolyzed Teffstraw

Analysis of variance (ANOVA) for the fitted quadraticmodel is shown in Table 5 e model summary for re-gression coefficients (R2 996 adjusted R2 991 andpredicted R2 975) shows that the quadratic model fitsinto the experimental data ANOVA study for the quadraticmodel was used to evaluate the impact and significance ofterms in the regression equation From the ANOVA results

shown in Table 5 the p values for all the linear and in-teraction coefficients are lt005 which shows that all vari-ables and their interaction have significant effect on dilutesulfuric acid hydrolysis of Teff straw e Lack of Fit with Fvalue and p value of 829 and 011 respectively indicates thatLack of Fit is not significant as compared to the pure error orin other words the model was significant

DF is the degree of freedom SS is the sum of squares MSis the mean square p values are significant at ple 005R2 0996 predicted R2 0975 adjusted R2 0991

e 3D surface plots (shown in Figure 7) which aregraphical representation of regression model equation (13)represent infinitive number of combinations of two testvariables with the third and fourth variables maintained atzero (center point) level e contours were plotted to

18

19

20

21

22

23

24

25

TRS

(mg

g)

90 100 110 120 130 14080Hydrolysis Temperature (degC)

30min40min

60min70min

Figure 4 e effect of hydrolysis temperature and hydrolysis time on the yield of total reducing sugar (TRS) from Teff straw (dilute sulfuricacid concentration 4 vv () and solid to liquid ratio 1 20)

05 vv(2 vv)(3 vv)

(4 vv)(5 vv)

16

18

20

22

24

26

TRS

(mg

g)

40 50 60 7030Time (min)

Figure 5 e effect of hydrolysis time and dilute sulfuric acid concentration on the yield of total reducing sugar (TRS) from Teff straw(hydrolysis temperature 120degC and solid to liquid ratio 1 20)


observe the interaction of two independent variables Anelliptical and elliptical nature contour plot are obtained bythe interaction of temperature and dilute sulfuric acidconcentration (Figure 7(a)) dilute sulfuric acid concentra-tion and hydrolysis time (Figure 7(b)) dilute sulfuric acidconcentration and liquid to solid ratio (Figure 7(c)) tem-perature and hydrolysis time (Figure 7(d)) temperature andliquid to solid ratio (Figure 7(e)) and liquid to solid ratioand hydrolysis time (Figure 7(f )) on the total reducing sugaryield depicting significant interaction between the variablesis is also confirmed by the F and p values of their in-teraction coefficients in the ANOVA analysis

e optimum conditions for dilute sulfuric acid hy-drolysis of Teff straw for maximum total reducing sugar yieldof 2665mgg under this model were as follows

concentration of H2SO4 4 vv temperature 120degC solidto liquid ratio 1 20 and hydrolysis time 55min

37 Validation of Experiments Optimum conditions formaximum total reducing sugar yield predicted by the BBDexperiments and RSM analysis have been corroborated byvalidation experiments of dilute sulfuric acid hydrolysis ofTeff straw e validation experiments were conducted intriplicate under optimized conditions (H2SO4 concen-tration 4 vv temperature 120degC hydrolysis time- 55min and solid to liquid ratio 1 20 gml) to ascertainreproducibility of results e results of validation experi-ment under the optimum conditions agreed well with modelpredictions

0

5

10

15

20

25

TRS

(mg

g)

115 120 130110Solid to Liquid Ratio

80degC100degC

120degC140degC

Figure 6 e effect of solid to liquid ratio and hydrolysis temperature on the yield of total reducing sugar (TRS) from Teff straw (dilutesulfuric acid concentration 4 vv () and hydrolysis time 60min)

Table 5 ANOVA for the quadratic model for dilute sulfuric acid hydrolysis of Teff straw

Source SS DF MS F value p valueModel 19491 14 1392 19674 lt00001A 9747 1 9747 137740 lt00001B 7154 1 7154 101098 lt00001C 1850 1 1850 26144 lt00001D 075 1 075 1060 00069AB 380 1 380 5374 lt00001AC 064 1 064 904 00109AD 090 1 090 1275 00038BC 036 1 036 509 00436BD 049 1 049 692 00219CD 030 1 030 497 00441A2 0049 1 0049 069 04217B2 9259E-003 1 9259E-003 013 07238C2 0063 1 0063 088 03655D2 9259E-005 1 9259E-005 1308E-003 09717Residual 085 12 0071Lack of Fit 083 10 0083 829 01123Pure error 0020 2 10E-002Corr total 19576 26


302826242220181614

120110

10090

80 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)

Temperature (degC) Acid concn (vv )

(a)

302826242220181614

6054

4842

3630 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)

Time (min) Acid concn (vv )

(b)

302826242220181614

3025

2015

10 0512

1926

334

Tota

l red

ucin

g su

gar (

mg

g)

Liquid to Soild (mlg) Acid concn (vv )

(c)

30

28

26

24

22

20

18

16

14

60 54 48 42 36 30 8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)

Time (min) Temperature (degC)

(d)

302826242220181614

8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)

Temperature (degC)30

2520

1510

Liquid to Soild (mlg)

(e)

302826242220181614To

tal r

educ

ing

suga

r (m

gg)

3025

2015

10


6054

4842

3630 Time (m

in)

(f)

Figure 7 Surface plots showing the effect of (a) temperature and dilute sulfuric acid concentration (b) dilute sulfuric acid concentrationand hydrolysis time (c) dilute sulfuric acid concentration and liquid to solid ratio (d) temperature and hydrolysis time (e) temperature andliquid to solid ratio and (f) liquid to solid ratio and hydrolysis time on the total reducing sugar yield


4 Conclusion

e morphological analysis using SEM showed that hy-drolyzed Teff straw with dilute sulfuric acid has more poresand distorted bundles than those of raw Teff straw XRDanalysis also showed that hydrolyzed Teff straw has highercrystallinity and smaller crystallite size than raw Teff strawwhich might be due to removal of hemicellulose amorphouscellulose and lignin components Under the optimizedconditions for dilute sulfuric acid hydrolysis of Teff straw(120degC 4 vv H2SO4 concentration 1 20 solid to liquidratio and 55min hydrolysis time) we have found a totalreducing sugar yield of 2665mgge results of the presentstudy showed that Teff straw is good potential lignocellulosicbiomass for the production of biofuels and value-addedchemicals

Abbreviations

ANOVA Analysis of varianceAR Analytical reagentBBD BoxndashBehnken designCI Crystalline indexDOE Design of experimentDSC Differential scanning calorimetryFC Fixed carbonFf Fehling factorFTIR Fourier transform infrared spectroscopyLCM Lignocellulose materialMC Moisture contentRS Reducing sugarRSM Response surface methodologySEM Scanning electron microscopyTRS Total reducing sugarVM Volatile matterXRD X-ray diffraction

Data Availability

e datasets generated andor analyzed during the currentstudy are available from the corresponding author on rea-sonable request

Conflicts of Interest

e authors do not have any conflicts of interest

Acknowledgments

e authors would like to thank Addis Ababa Science andTechnology University for allowing experimental setup workand analytical instruments for characterization

References

[1] M H Mengesha ldquoChemical composition of Teff (Eragrostistef) compared with that of wheat barley and grain sorghumrdquoEconomic Botany vol 20 no 3 pp 268ndash273 1966

[2] Z T Dame ldquoAnalysis of major and trace elements in Teff(Eragrostis tef)rdquo Journal of King Saud University-Sciencevol 32 no 1 pp 145ndash148 2020

[3] B Tsegaye C Balomajumder and P Roy ldquoAlkali pretreat-ment of wheat straw followed by microbial hydrolysis forbioethanol productionrdquo Environmental Technology vol 40no 9 pp 1203ndash1211 2019

[4] X Ji H Ma Z Tian et al ldquoProduction of xylose from dilutedsulfuric acid hydrolysis of wheat strawrdquo Bio Resources vol 12no 4 pp 7084ndash7095 2017

[5] F P Cardenas-Toro C S Alcazar-Alay T Forster-Carneiroand M A A Meireles ldquoObtaining oligo- and monosaccha-rides from agroindustrial and agricultural residues usinghydrothermal treatmentsrdquo Food and Public Health vol 4no 3 pp 123ndash139 2014

[6] P Kumar D M Barrett M J Delwiche and P StroeveldquoMethods for pretreatment of lignocellulosic biomass forefficient hydrolysis and biofuel productionrdquo Industrial ampEngineering Chemistry Research vol 48 no 8 pp 3713ndash37292009

[7] A B Wassie and V C Srivastava ldquoChemical treatment of Teffstraw by sodium hydroxide phosphoric acid and zinc chlo-ride adsorptive removal of chromiumrdquo International Journalof Environmental Science and Technology vol 13 no 10pp 2415ndash2426 2016

[8] R O Moutta A K Chandel R C L B Rodrigues M B SilvaG J M Rocha and M B Silva ldquoStatistical optimization ofsugarcane leaves hydrolysis into simple sugars by dilutesulfuric acid catalyzed processrdquo Sugar Tech vol 14 no 1pp 53ndash60 2012a

[9] J Zhuang Y Liu Z Wu Y Sun and L Lu ldquoHydrolysis ofwheat straw hemicellulose and detoxification of the hydro-lysate for xylitol productionrdquo Bio Resources vol 4 no 2pp 674ndash686 2009

[10] Q Zheng T Zhou Y Wang et al ldquoPretreatment of wheatstraw leads to structural changes and improved enzymatichydrolysisrdquo Scientific Reports vol 8 no 1 pp 1ndash9 2018

[11] A M Mansora S L Jeng A Farid Nasir H Hashima andW Shin Hoa ldquoCharacteristics of cellulose hemicellulose andlignin of MD2 pineapple biomassrdquo Chemical Engineeringvol 72 pp 79ndash84 2019

[12] J B Sluiter R O Ruiz C J Scarlata A D Sluiter andD W Templeton ldquoCompositional analysis of lignocellulosicfeedstocks review and description of methodsrdquo Journal ofAgricultural and Food Chemistry vol 58 no 16pp 9043ndash9053

[13] O A Adeeyo O M Oresegun and T E OladimejildquoCompositional analysis of lignocellulosic materials evalua-tion of an economically viable method suitable for woody andnon-woody biomassrdquo American Journal of Engineering Re-search vol 4 no 4 pp 14ndash19 2015

[14] N Dinh Vu H i Tran N D Bui C Duc Vu and H VietNguyen ldquoLignin and cellulose extraction from Vietnamrsquos ricestraw using ultrasound-assisted alkaline treatment methodrdquoInternational Journal of Polymer Science Article ID 10636958 pages 2017

[15] T Kunz E J Lee V Schiwek T Seewald and F J MethnerldquoGlucosendasha reducing sugar reducing properties of sugars inbeverages and foodrdquo Brewery Science vol 64 pp 61ndash67 2011

[16] K Tihomirova B Dalecka and L Mezule ldquoApplication ofconventional HPLC RI technique for sugar analysis inhydrolysed hayrdquo Agronomy Research vol 14 no 5pp 1713ndash1719 2016


[17] A Kurniati H Darmokoesoemo and N N Tri PuspaningsihldquoScanning electron microscope analysis of rice straw degra-dation by a treatment with α-L-arabinofuranosidaserdquo Pro-cedia Chemistry vol 18 pp 63ndash68 2016

[18] A Brys J Brys E Ostrowska-Ligeza et al ldquoWood biomasscharacterization by DSC or FT-IR spectroscopyrdquo Journal ofEermal Analysis and Calorimetry vol 126 no 1 pp 27ndash352016

[19] P Lenihan A Orozco E Orsquoneill M N M AhmadD W Rooney and G M Walker ldquoDilute acid hydrolysis oflignocellulosic biomassrdquo Chemical Engineering Journalvol 156 no 2 pp 395ndash403 2010

[20] B Z Tizazu and V S Moholkar ldquoKinetic and thermodynamicanalysis of dilute acid hydrolysis of sugarcane bagasserdquoBioresource Technology vol 250 pp 197ndash203 2018

[21] S Inna J Yvette and K Richard ldquoEnergy potential of wastederived from some food crop products in the northern part ofCameroonrdquo International Journal of Energy and Power En-gineering vol 4 no 6 p 342 2015

[22] M M Adeyemi R S Olatubosun O A Babarinde andP E Omale ldquoComparative study of bioethanol productionfrom wheat straw and rice strawrdquo Journal of Chemical Societyof Nigeria vol 44 no 2 2019

[23] B Patel and B Gami ldquoBiomass characterization and its use assolid fuel for combustionrdquo Iranica Journal of Energy amp En-vironment vol 3 no 2 pp 123ndash128 2012

[24] M Danish M Naqvi U Farooq and S Naqvi ldquoCharacter-ization of South Asian agricultural residues for potentialutilization in future ldquoenergy mixrdquordquo Energy Procedia vol 75pp 2974ndash2980 2015

[25] S Sadaka M A Sharara A Ashworth P Keyser F Allen andA Wright ldquoCharacterization of biochar from switchgrasscarbonizationrdquo Energies vol 7 no 2 pp 548ndash567 2014

[26] A O Jimoh M M Namadi K Ado and B MuktarldquoProximate and ultimate analysis of Eichornia natans (waterhyacinth) Pistia stratiotes (water lettuce) andNymphaea lotus(water Lily) in the production of biofuelrdquo Advced AppliedScience Research vol 7 no 4 pp 243ndash249 2016

[27] B T Shawky N B Talaat and S Mohapatra ldquoConversion ofrice straw to fermentable sugars and bioethanol by Mfexpretreatment and sequential fermentationrdquo InternationalJournal of Science and Technology vol 3 no 2 pp 356ndash3802017

[28] B Wanitwattanarumlug A Luengnaruemitchai andS Wongkasemjit ldquoCharacterization of corn cobs from mi-crowave and potassium hydroxide pretreatmentrdquo Interna-tional Journal of Chemical Molecular Nuclear Materials andMetallurgical Engineering vol 6 no 4 pp 354ndash358 2012

[29] J G Reales-Alfaro L T Daza G Arzuaga-LindadoH I Castantildeo-Pelaez and A D Polo-Cordoba ldquoAcid hy-drolysis of water hyacinth to obtain fermentable sugarsrdquo CTand F Ciencia Tecnologia Futuro vol 5 no 2 pp 101ndash1112013

[30] M Tayyab A NomanW Islam et al ldquoBioethanol productionfrom lignocellulosic biomass by environment-friendly pre-treatment methods a reviewrdquo Applied Ecological Environ-ment Research vol 16 no 1 pp 225ndash249 2018


such as extractives and ash Due to its heterogeneouscomposition hemicellulose is of particular interest toresearchers ie hemicellulose is branched heteropolymerswith a degree of polymerization of around 80 to 200 and isdepolymerized into its monomeric units mainly xyloseand their subsequent conversion into biofuels and value-added products via microbial fermentation [3] Pretreat-ment is the crucial stage in the transformation of ligno-cellulosic biomass to fermentable sugars It is vital to alterthe structure of cellulosic biomass for hydrolysis is isdue to the crystallinity of cellulose degree of polymeri-zation moisture content available surface area and lignincontent [4] Pretreatment has been recognized as one ofthe most expensive processing steps in lignocellulosicbiomassndashtondashfermentable sugars conversion e goals ofany pretreatment are (1) the increase of the surface areaand porosity (2) modification of lignin structure andremoval of lignin (3) depolymerization of hemicelluloseand removal of hemicellulose and (4) reduction of thecrystallinity of cellulose An effective pretreatment should(1) avoid the need for reducing the size of biomass particle(2) preserve the pentose (hemicellulose) fractions (3) limitthe formation of degradation products that inhibit thegrowth of fermentative microorganism and (4) minimizeenergy demands in addition the pretreatment agentshould have low cost and be capable of recycling inex-pensively [5] Pretreatment with concentrated acids suchas hydrochloric acid and sulfuric acid can result in en-hancement of enzymatic hydrolysis of lignocellulosicbiomass to produce fermentable sugars Even though theyare strong agents for cellulose hydrolysis concentratedacids are toxic corrosive and hazardous and thus requirereactors that are resistant to corrosion which makes thepretreatment process very expensive In addition theconcentrated acid must be recovered after hydrolysis tomake the process economically feasible [6 7] Dilute acidhydrolysis has been widely used for pretreatment of lig-nocellulosic biomass is is due to high hydrolysis ratebeing specific toward hemicellulose and being moreeconomical than enzymatic concentrated acid and basepretreatment [8] e yield of fermentable sugars duringacid hydrolysis is affected by various factors such as hy-drolysis time solid to liquid ratio hydrolysis temperatureand acid concentration Dilute sulfuric acid hydrolysis isthe most common and effective pretreatment process forTeff straw [9] but other reagents such as hydrochloricnitric and phosphoric acids can also be used Variousresearch works have been done on optimization of diluteacid hydrolysis of different lignocellulosic biomass usingresponse surface methodology Limited reports have beenobtained on the optimization of dilute acid hydrolysis ofTeff straw to produce total fermentable sugars using re-sponse surface methodology e conventional method ofoptimization involves varying one factor at a time andkeeping the others constant It might be useful but does notexplain the effects of interaction between the variousfactors under consideration us the response surface

methodology which is a collection of mathematical andstatistical techniques for empirical modeling was used foroptimization of dilute sulfuric acid hydrolysis of Teff strawfor total reducing sugar production e present studyaimed to statistically optimize the process parameters (vizsulfuric acid concentration or load hydrolysis tempera-ture hydrolysis time and solid to liquid ratio) of dilutesulfuric acid hydrolysis of Teff straw Prior to responsesurface methodology followed by BoxndashBehnken design(BBD) optimization of dilute sulfuric acid hydrolysis ofTeff straw the composition of Teff straw was first analyzedBoxndashBehnken design (BBD) has been used to design andoptimize the process parameters of dilute sulfuric acidhydrolysis conditions and the interaction among theseparameters on dilute acid hydrolysis of Teff straw to obtainmaximum total reducing sugars yield

2 Materials and Methods

21 Materials and Chemicals Teff straw was collected fromDebre Zeyit Oromia Region Ethiopia as the raw materialfor total reducing sugar production All chemicals and re-agents used throughout this study were of analytical reagent(AR) grade and maximum purity from HiMedia and Ran-chem India e reagents were obtained from AtomicEducational Materials Supply PLC Sulfuric acid hydro-chloric acid and methylene blue indicator (purity 98 37and 100 respectively) were obtained from Blulux Labo-ratories Pvt Ltd In addition potassium hydroxide (9808pure HiMedia Laboratories Pvt Ltd) was required to de-termine the total reducing sugar by Fehling solutionmethodSodium hydroxide (9808 pure HiMedia Laboratories PvtLtd) was employed for determination of hemicellulosecontent of Teff straw whereas sulfuric acid H2SO4 (LOBAChemie purity 98) was used to determine the lignincontent

22 Collection and Preparation of Teff Straw Teff strawcollected from Debre Zeyit Oromia Region Ethiopia waswashed three times in order to remove soluble componentsand dust particles It was then sun-dried for two days for thenext size reduction process e dried Teff straw was groundand screened using a standard sieve for the average particlesize of 710 μm (071mm) e particle size was taken basedon the previous literature reported elsewheree sieved Teffstraw was stored in a zipped lock plastic bag at ambienttemperature until use

23 ProximateAnalysis of Teff Straw e proximate analysisof Teff straw viz moisture content total ash content totalvolatile matter and fixed carbon was determined usingstandard procedures of gravimetric methods

231 Determination of Moisture Content is was done bythe gravimetric method About 15 gram of finely pow-dered Teff straw was weighed into the silica crucible then



MC() g minus x

g1113888 1113889 times 100 (1)



weight of crucible

Ash() w1 minus w2

w1times 100 (2)





(3)















(5)





V4 times W

(6)






(7)


βT βD + βε (8)


D Kλ

βD cos θ (9)






(11)





























+ 003A2




2+ 003AB + 002AC



(13)








(a) (b)


1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

157

622

38

344

837

78

439

6

643

2

774

2

(a)

1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

160

822

16

349

437

74

439

8

643

6

774

6

(b)


14

16

18

20

22

24

26

TRS

(mg

g)


100degC120degC

140degC80degC








18

19

20

21

22

23

24

25

TRS

(mg

g)


30min40min

60min70min


05 vv(2 vv)(3 vv)

(4 vv)(5 vv)

16

18

20

22

24

26

TRS

(mg

g)

40 50 60 7030Time (min)







0

5

10

15

20

25

TRS

(mg

g)


80degC100degC

120degC140degC





302826242220181614

120110

10090

80 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(a)

302826242220181614

6054

4842

3630 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(b)

302826242220181614

3025

2015

10 0512

1926

334

Tota

l red

ucin

g su

gar (

mg

g)


(c)

30

28

26

24

22

20

18

16

14

60 54 48 42 36 30 8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


(d)

302826242220181614

8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


2520

1510


(e)

302826242220181614To

tal r

educ

ing

suga

r (m

gg)

3025

2015

10


6054

4842

3630 Time (m

in)

(f)



4 Conclusion


Abbreviations


Data Availability




Acknowledgments


References


































MC() g minus x

g1113888 1113889 times 100 (1)



weight of crucible

Ash() w1 minus w2

w1times 100 (2)





(3)















(5)





V4 times W

(6)






(7)


βT βD + βε (8)


D Kλ

βD cos θ (9)






(11)





























+ 003A2




2+ 003AB + 002AC



(13)








(a) (b)


1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

157

622

38

344

837

78

439

6

643

2

774

2

(a)

1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

160

822

16

349

437

74

439

8

643

6

774

6

(b)


14

16

18

20

22

24

26

TRS

(mg

g)


100degC120degC

140degC80degC








18

19

20

21

22

23

24

25

TRS

(mg

g)


30min40min

60min70min


05 vv(2 vv)(3 vv)

(4 vv)(5 vv)

16

18

20

22

24

26

TRS

(mg

g)

40 50 60 7030Time (min)







0

5

10

15

20

25

TRS

(mg

g)


80degC100degC

120degC140degC





302826242220181614

120110

10090

80 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(a)

302826242220181614

6054

4842

3630 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(b)

302826242220181614

3025

2015

10 0512

1926

334

Tota

l red

ucin

g su

gar (

mg

g)


(c)

30

28

26

24

22

20

18

16

14

60 54 48 42 36 30 8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


(d)

302826242220181614

8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


2520

1510


(e)

302826242220181614To

tal r

educ

ing

suga

r (m

gg)

3025

2015

10


6054

4842

3630 Time (m

in)

(f)



4 Conclusion


Abbreviations


Data Availability




Acknowledgments


References




































(5)





V4 times W

(6)






(7)


βT βD + βε (8)


D Kλ

βD cos θ (9)






(11)





























+ 003A2




2+ 003AB + 002AC



(13)








(a) (b)


1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

157

622

38

344

837

78

439

6

643

2

774

2

(a)

1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

160

822

16

349

437

74

439

8

643

6

774

6

(b)


14

16

18

20

22

24

26

TRS

(mg

g)


100degC120degC

140degC80degC








18

19

20

21

22

23

24

25

TRS

(mg

g)


30min40min

60min70min


05 vv(2 vv)(3 vv)

(4 vv)(5 vv)

16

18

20

22

24

26

TRS

(mg

g)

40 50 60 7030Time (min)







0

5

10

15

20

25

TRS

(mg

g)


80degC100degC

120degC140degC





302826242220181614

120110

10090

80 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(a)

302826242220181614

6054

4842

3630 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(b)

302826242220181614

3025

2015

10 0512

1926

334

Tota

l red

ucin

g su

gar (

mg

g)


(c)

30

28

26

24

22

20

18

16

14

60 54 48 42 36 30 8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


(d)

302826242220181614

8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


2520

1510


(e)

302826242220181614To

tal r

educ

ing

suga

r (m

gg)

3025

2015

10


6054

4842

3630 Time (m

in)

(f)



4 Conclusion


Abbreviations


Data Availability




Acknowledgments


References





































(11)





























+ 003A2




2+ 003AB + 002AC



(13)








(a) (b)


1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

157

622

38

344

837

78

439

6

643

2

774

2

(a)

1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

160

822

16

349

437

74

439

8

643

6

774

6

(b)


14

16

18

20

22

24

26

TRS

(mg

g)


100degC120degC

140degC80degC








18

19

20

21

22

23

24

25

TRS

(mg

g)


30min40min

60min70min


05 vv(2 vv)(3 vv)

(4 vv)(5 vv)

16

18

20

22

24

26

TRS

(mg

g)

40 50 60 7030Time (min)







0

5

10

15

20

25

TRS

(mg

g)


80degC100degC

120degC140degC





302826242220181614

120110

10090

80 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(a)

302826242220181614

6054

4842

3630 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(b)

302826242220181614

3025

2015

10 0512

1926

334

Tota

l red

ucin

g su

gar (

mg

g)


(c)

30

28

26

24

22

20

18

16

14

60 54 48 42 36 30 8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


(d)

302826242220181614

8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


2520

1510


(e)

302826242220181614To

tal r

educ

ing

suga

r (m

gg)

3025

2015

10


6054

4842

3630 Time (m

in)

(f)



4 Conclusion


Abbreviations


Data Availability




Acknowledgments


References

















































+ 003A2




2+ 003AB + 002AC



(13)








(a) (b)


1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

157

622

38

344

837

78

439

6

643

2

774

2

(a)

1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

160

822

16

349

437

74

439

8

643

6

774

6

(b)


14

16

18

20

22

24

26

TRS

(mg

g)


100degC120degC

140degC80degC








18

19

20

21

22

23

24

25

TRS

(mg

g)


30min40min

60min70min


05 vv(2 vv)(3 vv)

(4 vv)(5 vv)

16

18

20

22

24

26

TRS

(mg

g)

40 50 60 7030Time (min)







0

5

10

15

20

25

TRS

(mg

g)


80degC100degC

120degC140degC





302826242220181614

120110

10090

80 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(a)

302826242220181614

6054

4842

3630 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(b)

302826242220181614

3025

2015

10 0512

1926

334

Tota

l red

ucin

g su

gar (

mg

g)


(c)

30

28

26

24

22

20

18

16

14

60 54 48 42 36 30 8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


(d)

302826242220181614

8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


2520

1510


(e)

302826242220181614To

tal r

educ

ing

suga

r (m

gg)

3025

2015

10


6054

4842

3630 Time (m

in)

(f)



4 Conclusion


Abbreviations


Data Availability




Acknowledgments


References



































(a) (b)


1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

157

622

38

344

837

78

439

6

643

2

774

2

(a)

1800

1600

1400

1200

1000

800

600

400

200

0

Inte

nsity

0 10 20 30 40 50 60 70 80 902θ (degree)

160

822

16

349

437

74

439

8

643

6

774

6

(b)


14

16

18

20

22

24

26

TRS

(mg

g)


100degC120degC

140degC80degC








18

19

20

21

22

23

24

25

TRS

(mg

g)


30min40min

60min70min


05 vv(2 vv)(3 vv)

(4 vv)(5 vv)

16

18

20

22

24

26

TRS

(mg

g)

40 50 60 7030Time (min)







0

5

10

15

20

25

TRS

(mg

g)


80degC100degC

120degC140degC





302826242220181614

120110

10090

80 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(a)

302826242220181614

6054

4842

3630 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(b)

302826242220181614

3025

2015

10 0512

1926

334

Tota

l red

ucin

g su

gar (

mg

g)


(c)

30

28

26

24

22

20

18

16

14

60 54 48 42 36 30 8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


(d)

302826242220181614

8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


2520

1510


(e)

302826242220181614To

tal r

educ

ing

suga

r (m

gg)

3025

2015

10


6054

4842

3630 Time (m

in)

(f)



4 Conclusion


Abbreviations


Data Availability




Acknowledgments


References






































18

19

20

21

22

23

24

25

TRS

(mg

g)


30min40min

60min70min


05 vv(2 vv)(3 vv)

(4 vv)(5 vv)

16

18

20

22

24

26

TRS

(mg

g)

40 50 60 7030Time (min)







0

5

10

15

20

25

TRS

(mg

g)


80degC100degC

120degC140degC





302826242220181614

120110

10090

80 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(a)

302826242220181614

6054

4842

3630 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(b)

302826242220181614

3025

2015

10 0512

1926

334

Tota

l red

ucin

g su

gar (

mg

g)


(c)

30

28

26

24

22

20

18

16

14

60 54 48 42 36 30 8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


(d)

302826242220181614

8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


2520

1510


(e)

302826242220181614To

tal r

educ

ing

suga

r (m

gg)

3025

2015

10


6054

4842

3630 Time (m

in)

(f)



4 Conclusion


Abbreviations


Data Availability




Acknowledgments


References





































0

5

10

15

20

25

TRS

(mg

g)


80degC100degC

120degC140degC





302826242220181614

120110

10090

80 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(a)

302826242220181614

6054

4842

3630 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(b)

302826242220181614

3025

2015

10 0512

1926

334

Tota

l red

ucin

g su

gar (

mg

g)


(c)

30

28

26

24

22

20

18

16

14

60 54 48 42 36 30 8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


(d)

302826242220181614

8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


2520

1510


(e)

302826242220181614To

tal r

educ

ing

suga

r (m

gg)

3025

2015

10


6054

4842

3630 Time (m

in)

(f)



4 Conclusion


Abbreviations


Data Availability




Acknowledgments


References

































302826242220181614

120110

10090

80 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(a)

302826242220181614

6054

4842

3630 05 12 19 26 33 4

Tota

l red

ucin

g su

gar (

mg

g)


(b)

302826242220181614

3025

2015

10 0512

1926

334

Tota

l red

ucin

g su

gar (

mg

g)


(c)

30

28

26

24

22

20

18

16

14

60 54 48 42 36 30 8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


(d)

302826242220181614

8090

100110

120

Tota

l red

ucin

g su

gar (

mg

g)


2520

1510


(e)

302826242220181614To

tal r

educ

ing

suga

r (m

gg)

3025

2015

10


6054

4842

3630 Time (m

in)

(f)



4 Conclusion


Abbreviations


Data Availability




Acknowledgments


References

































4 Conclusion


Abbreviations


Data Availability




Acknowledgments


References

































ReducingSugarProductionfrom Teff StrawBiomassUsingDilute ...

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