Indian Journal of Chemical Technology Vol. 10, November 2003, pp. 587-592

Articles

Preservation of bagasse through biotech approach for pulp and paper industry

K R Yadav, Rajesh K Sharma & R M Kothari*

Prathista R&D Centre, 1 0- 1 70/23, Bharathi Nagar, Temple Alwal, Secunderabad 500 0 1 0, India

Received 30 October 2002; revised received 9 April 2003; accepted 20 May 2003

Bagasse, a by-product of sugarcane industry, has potential to serve as a source of ceUulosic fibre for paper making. For its consumption throughout the year, bagasse needs to be preserved for at least 6-8 months. The use of chemicals for preservation of bagasse lias been found unsafe in practice, hazardous for health and polluter of eco­system. An attempt has been made. to preserve bagasse through biotechnological approaches. For this purpose, bagasse was exposed to 'three plant�derived, anti-microbial powders, individually aIJd cumulatively, with and without organic acid producing' bacteria. The exposed bagasse was preserved for 6 mbnths, under ambient conditions mimicking the storage in paper millS. Subsequently, it was subjected to physical, chemical and microbiological examination to evaluate the effect . of .each preservative. It was observed that neem leaf powder exposure in conjunction with acid prOducing'bacteria afforaed maximum preservative effect on bagasse, as it retained necessary characteristics desired for good quiilitY pulp milldng.

Significant amount of bagasse generated by sugarcane industry is used in boiler for generating energy; however, its low bulk density, high surface area and high moisture content forbids efficient energy recovery due to inefficient combustion. This is especially so as only the pith generates 93% of the total energy of bagasse, while its epidermis and fibrous portion contribute only 7% energy. Besides this inefficient application, bagasse does not have any alternative economical value-added usage appealing the industry. Logically, it makes a prudent business judgement to use (i) epidermis for manufacturing cardboards only, (ii) fibrous portion for serving as a source of cellulosic fibre for pulp making only and (iii) pith for burning in fluidized bed boilers only for the recovery of 93% energy. Incidentally, this strategy makes a good sense from environmental point of view also ' .

Bamboo and soft woods have been traditionally preferred raw materials in pulp and paper industry . Since supply of these conventional raw materials is fast depleting, bagasse deserves serious consideration as an important alternative renewable resource material. With the increasing demand for paper due to increasing population, indiscriminate felling of bamboo and woods could be largely arrested by

*For correspondence: Jain Irrigation Systems Ltd, Food Park, Jain Valley. Jalgaon 425 001 , India (E-mail : foodparkjal @sancharnet.com; Fax: 0257-226 1 1 1 1122)

substituting the use of bagasse fibre due to its i nherent characteristics such as (i) short duration required for its perennial replenishment, (ii) easy and abundant availability, (iii) economical appeal to pulp industry and (iv) least need for engineering changes in pulp mills.

Logistically too, India being the largest producer of sugarcane2, use of around 40 million tonnes bagasse generated every year would be preferred once its preservation technology is devised for storage for about 6-8 months, when it is not available during non­crushing season. Such a strategy of preservation is anticipated to arrest microbial deterioration of bagasse, consequently affording the paper industry advantages of (i) consuming normal quantum of pulping chemicals and energy, (ii) giving reasonably white coloured pulp, (iii) affording yield of pulp comparable to that of fresh bagasse, (iv) rendering bleachability of pulp with an equal ease and (v) bringing remunerative realization commensurate with the cost of manufacturing paper'

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Towards this objective, a number of studies have been carried out to preserve bagasse using (i) wet bulk 80% moisture, (ii) TNPL process, (iii) dry bulk storage, (iv) bales and (v) 20% moisture ' . In th is communication, the possibility of bagasse preservation by using plant-derived natural anti­microbial principles and lactic acid producing bacteria, individually or collectively has been explored.

Articles

Experimental Procedure

Bagasse

Fresh bagasse was collected from a nearby sugar mill; its chemical and physical properties were analysed by standard methods.

Preservatives

Neem (Azadirachta indica) leaves, calotropis (Calotropis procera) leaves, tobacco (Nicotiana tabacum) leaves, collected from local farms, dried under shade at 35±2°C until complete drying (5% moisture), pulverized, sieved for 100 mesh size and used for preservation studies.

Microbial culture

Lactobacillus delbruckii was taken from MIs Prathista Biotech. Ltd., Secunderabad.

Chemicals and reagents

Fertilizer grade DAP (Godavari Fertilizers Ltd., Hyderabad), corn steep liquor (CSL; Sukhjeet Starch Mills, Phagawara), commercial grade calcium carbonate (lai Murthy Chemicals, Salem), dextrose (Prathista Bio-Tech. Ltd., Choutuppal) and demineralized (DM) water were used.

Inoculum preparation

It was prepared in 1 L medium, compnsmg of dextrose, 2%; DAP, 0. 1 %; CSL, 1 % and calcium carbonate, 1 %; pH adjusted to 7 .0, sterilized ( 1 2 1 °C, 20 min), cooled to 45°C and inoculated with L. delbruckii culture. It was grown ( 45°C, 50 rpm, 24 h) on an incubator shaker.

Experimental set-up for preservation

Five stacks, each of 200 kg bagasse, were prepared for experimentation. While stack one served as a control (treated with 50 L water), three stacks were treated with 50 L of 2% (w/v) leaf powder from neem, calotropis and tobacco dispersed in water and fifth stack with 2% inoculum (24 h old, 1x 109 cells per mL) of lactobacilli culture dispersed in 50 L water, by thoroughly spraying in such a way that each particle of bagasse was wet with the respective preservatives.

These stacks were maintained undisturbed at atmospheric temperature throughout the preservation duration of 6 months (May-October), when relative humidity fluctuated from 30-96% as a function of storage period. A representative sample from each stack was removed once per month for analysis to determine the efficacy of preservation.

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In another set of experiment, each experimental stack of 200 kg bagasse was sprayed with 2% inoculum (24 h old, l x 1 09 cells per mL) of lactobacilli culture dispersed in 50 L water, in such a way that each particle of bagasse was wet. subsequently incubated at ambient temperature for four days and afterwards similarly sprayed with anti­microbial principles from neem, calotropis and tobacco in the same manner as above. These stacks along with control were maintained in the same manner and sampling was also done at the same frequency in the same fashion.

Monitoring of preservation

Physical characteristics (fibre and pith contents ) of bagasse were monitored3. Chemical characteri stics such as pH, moisture, cellulose4 hemicel lu lose). reducing sugars6 and lignin contene were esti mated by standard methods. Microbial characteristics were also monitored8.

Results and Discussion To evaluate the effect of the above mentioned

preservatives, representative samples of treated bagasse, collected at monthly frequency, were analyzed. Their profiles monitored for preservation up to six months are summarized in Table 1 -6. The data presented in tables is in weight %.

Effect of preservatives on fibre and pith content

On the basis of a trend of fibre and pith analysis (Table 1 ), it is apparent that in control, microbial degradation of fibre has already set in from first month onwards and its pronounced effect is distinctly seen after four months of storage, whereas neem leaf powder, tobacco leaf dust and L. delbruckii have shown comparable preservative effect, whi le calotropis exhibited least preservation. After fi ve and six months of storage, analysis indicated that neem leaf powder gave the best preservative effect as compared to tobacco dust, L. delbruckii and calotropis, individually.

The second set of experiments was concei vee! to explore if neem leaf powder in conjunction with L. delbruckii shows a synergistic effect. This was found to be the best preservative compared with either tobacco or calotropis . It has been observed that regardless of the preservatives, level of fibre declined while that of pith concomitantly increased, grossly reflecting percentage degradation of fibre, which is of interest to paper mills.

Yadav et al. : Preservation of bagasse through biotech approach Articles

Table I -Profiles of fibre and pith during the preservation of bagasse as a function of treatments

Months Treatments Control Neem CalotroEis Tobacco L. delbmckii

F P F P F P F P F P

Set I Initial 62. 1 33.2 6 1 .9 33.7 62.4 33.0 62.7 33.5 6 1 .8 33. 1 I 59.2 35. 1 60.2 33.9 57. 1 37. 1 6 1 .7 34. 1 59.9 34.8 2 54. 1 37.2 59.4 34.2 55.3 38.9 6 1 .3 34.5 57.8 35.2 3 52.2 39. 1 58.9 35.2 52.0 4 1 .0 60.7 35.0 56.7 35 .9

4 49.7 40.5 57.3 36.8 50.4 42.0 58.5 37.0 55.0 37. :' 5 47.0 4 1 .7 56.9 37.2 45.5 43.7 56.5 37.2 54.8 37 .5

6 45.0 43.5 56.5 38.0 44.9 44. 1 55.0 39.0 54.8 3R.O Set II

Initial 61 .5 34. 1 6 1 .3 34.0 6 1 .0 34.2 6 1 .2 34.3 I 55.7 36.5 60. 1 35.3 57.5 35.3 59.5 35.0 2 52.5 37.2 59.5 36.0 56.3 36.4 57.2 36.5 3 49.7 38.4 59.2 36.5 54.0 37.8 55.7 37.4 4 46. 1 39.8 58.4 37.2 52.5 39. 1 55.2 38.3 5 45.3 4 1 .2 57.9 37.6 5 1 .0 40.6 54.3 39.5 6 44.2 43.8 57.5 37.9 5 1 .0 4 1 .5 53.4 40.3

F = Fibre; P = Pith ; Values represented % by weight.

Table 2-Profiles of cellulose and hemicellulose during the preservation of bagasse as a function of treatments

Months Treatments Control Neem CalotroEis Tobacco L. delbruckii

C H C H C H C H C H

Set I

Initial 44.2 22.5 43.7 2 1 .7 44. 1 23.2 44.5 28.8 44.0 23. 1 1 4 1 .8 20.2 42.5 19.7 4 1 .6 20. 1 43.5 2 1 .7 43. 1 2 1 .5 2 40. 1 20.0 42. 1 19.0 40.0 19.6 43.0 29.0 4 1 .6 2 1 . 1

3 38.9 1 8.8 4 1 .7 1 8.5 37.5 19.0 42. 1 20.8 4 1 .0 20.5 4 38.0 1 8.0 4 1 .0 1 7.9 36.5 18.0 4 1 .2 19.6 4 1 .0 20.5 5 36.2 1 7.3 40.3 1 7.5 35. 1 17 . 1 40.0 17.9 4 1 .0 1 9. 7

6 35.5 1 6.5 39.7 1 7.0 33.5 1 6.3 39.0 16.8 39.9 1 9.3 Set II

Initial 43.8 2 1 .7 42.9 2 1 .5 43.2 I 40.3 2 1 .0 42.S 20.S 4 1 .2 2 3S.5 20. 1 4 1 .0 20. 1 40.9 3 36.4 1 9.5 4 1 .3 20.3 40.3 4 34.7 I S.2 43.6 19.6 39. 1 5 36.6 I S.0 42. 1 I S.9 37.S 6 33.3 17.0 42.S 1 8.S 36.7

C = Cellulose; H= Hemicellulose ; Values represented % by weight.

Effect of preservatives on cellulose and hemicellulose content

It is clear from Table 2 that as compared to control and calotropis, neem leaf powder has afforded more preservative effect comparable to that of tobacco dust and L. delbruckii individually; however, it is superior to both when the preservation was in conjunction with four days prior incubation by the culture of L.

delbruckii. This treatment reflected their synergistic effect, corroborated by the profiles of fibre in Table 1 . Thus, observations made on % fibre are corroborated with % cellulose + hemicellulose content.

2 1 . 1 43.7 2 1 .8 20.4 4 1 .7 20.2 19.2 42.0 19.7 I S.9 40.9 19. 1 17.2 3S.2 I S.7 17.0 36.9 1 8.2 16.5 34. 1 18.0

Effect of preservatives on reducing sugars alld lignin content

From Table 3, it is clear that regardless of the nature of preservatives, level of reducing sugars has gone down to almost zero, supporting a contention that the same was used by microbial growth (Table 4). which in turn was responsible for the degradation of fibre/cellulose/hemicelluloseibagasse. It is surprising that lignin too showed a degradative trend in both the sets, even neem could not arrest its degradation. From these profiles, it is concluded that ligninase-rich microbes (fungi) must have infested bagasse.

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Table 3-Profiles of reducing sugars and lignin during the preservation of bagassee as a function of treatments

Months Treatments Control Neem Calotro�is Tobacco L. delbruckii

R L R L R L R L R L

Set I

I ni t ial 1 . 1 1 9.2 1 .0 20. 1 1 .2 1 9.7 1 .0 1 9.6 1 .3 :20.4 I 0.7 1 8.8 1 .0 1 9.5 0.8 1 8.2 1 .0 19 . 1 0.3 1 9.0

2 0.6 1 8.0 0.8 1 9. 1 0.3 1 7.5 0.9 1 8.7 0.3 1 9.0

3 0.5 1 7.5 0.7 1 8.6 0.2 17 . 1 0.7 1 8. 1 0. 1 1 8.5 4 0.3 1 7.0 0.5 1 8.0 0. 1 16.5 0.4 1 7.5 0. 1 1 8.0

5 0.2 1 6. 5 0.3 1 7.2 0. 1 1 6.0 0.3 1 6.9 0. 1 1 6.5 6 0. 1 1 5 .5 0.2 1 6.8 0 . 1 1 5 .5 0.2 1 5.9 0. 1 1 6.2

Set II

Ini tial 0.9 18.9 1 .0 1 9.2 0.8 19.0 1 .0 19 . 1 I 0.4 1 8.5 0.4 1 9.0 0.3 1 8.7 0.3 1 8.8 2 0.3 1 8.0 0.3 1 8.7 0.2 1 7.9 0.2 18 . 1 3 0.2 1 7.3 0.2 1 8.2 0.2 1 7 . 1 0.2 1 7.7 4 0.2 1 6.8 0. 1 1 8.0 0. 1 1 6.8 0.2 1 7 . 1 5 0. 1 1 6. 1 0. 1 1 7.6 0. 1 1 6.2 0. 1 1 6.7 6 0. 1 1 5 .7 0. 1 1 7 . 1 0. 1 1 5 .5 0. 1 1 6.0

R= Reducing sugars; L= Lignin; Values represented % by weight.

Table 4-Profiles of bacterial and fungal count during the preservation of bagasse as a function of treatments

Months Treatments Control Neem Calotro�is Tobacco L.delbruckii

B F B F B F B F B F Set I

Initial 1 1 6 8 1 20 1 0 1 35 1 2 1 27 1 1 1 1 8 1 2 I 1 05 1 0 9 1 4 1 20 1 5 75 3 1 1 0 4 2 97 9 72 5 1 I5 1 I 60 4 100 3 3 75 8 57 6 90 1 0 57 5 85 3 4 65 9 50 7 70 1 0 55 7 55 3 5 59 1 0 49 8 57 1 0 60 9 50 3 6 55 1 I 50 9 60 1 0 67 1 0 52 3

Set II

Initial 1 35 1 2 1 30 1 1 1 29 1 1 1 32 1 0 I 1 25 1 5 1 05 5 1 17 8 1 1 2 7 2 97 1 2 75 5 95 9 89 8 3 83 I I 65 4 67 9 72 9 4 79 1 0 63 4 62 1 0 70 8 5 63 1 0 58 4 60 1 0 80 8 6 70 9 46 5 79 1 2 80 10

B= Bacterial count (x 1 09 /kg) ; F = Fungal count (x I 05/kg); Values represented % by weight.

responsible for its overall degradation as noticed during the preparation of soil conditioner9• Incidentally, it appeared that ligninase-rich white rot fungi co-habited comfortably with yeast which comes as a natural infestant of bagasse from sugar factory, rich in invertase for the consumption sugar and reducing sugars.

Effect of preservatives on bacterial and fungal count A general trend of reducing bacterial as well as

fungal count (Table 4), seen regardless of treatments

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in set I and II, is rather strange. It may be a retlection of total consumption of reducing sugars as a source of energy for multiplication as anticipated. From the trend of \flacterial and fungal profiles, calotropis appeared least effective, tobacco more effective and neem most effective.

Effect of preservatives on solubles From Table 5 , a trend of consistently reducing

moisture content is witnessed, presumably due to atmospheric evaporative effect. That solubles have

Yadav et al. : Preservation of bagasse through biotech approach Articles

Table 5-Profiles of moisture and solubles during preservation of bagasse as a function of treatments

Months Treatments Control Neem CalotroEis Tobacco L. delbruckii

M S M S M S M S M S

Set I

Initial 63.8 5.7 64.5 6. 1 65.0 6.9 63.9 6.5 64.7 6.4 I 58.7 9.2 59.5 8.5 57.5 10.2 59.3 7.5 58.2 8. 1 2 55.3 1 0.2 54.2 9. 1 53.4 1 1 .3 55. 1 8.2 54.8 9.3 3 53. 1 1 1 .0 5 1 .7 10 . 1 50.2 1 1 .5 53. 1 9.5 5 1 .3 1 0.2 4 50.8 10.2 50.0 10.0 49.0 1 2.0 5 1 .0 10.0 49.3 1 0.7 5 47.2 1 0.5 48. 1 9.7 47.9 1 1 .0 50.0 8 . 1 49.5 9. 7 6 45. 1 1 1 .5 44.5 6.5 43.7 1 0.2 45.5 6.7 42.5 8.2

Set II

Initial 60.5 6.5 60.8 6.6 6 1 .0 6.8 60.9 7.2 I 55.8 9.5 55.2 5.9 55.5 6.4 55. 1 6.5 2 52.7 1 0.2 53.0 5.7 52.8 8.0 53.2 7.5 3 50.5 1 0.5 5 1 .7 6.7 50.4 8.7 50.9 7.9 4 47.2 1 1 .2 49.8 6.6 47.9 8.2 48.2 7.7 5 44.7 1 2 . 1 47.3 5.9 43.9 8 . 1 46.9 7.9 6 42.9 1 1 .9 43.5 6.3 42.5 8.9 43.7 8.5

M= Moisture; S= Solubles; Values represented % by weight.

Table 6-Profiles of temperature and pH during the preservation of bagasse as a function of treatments

Months Treatments Control Neem CalotroEis Tobacco L. delbruckii

T pH T pH T pH T pH T pH

Set I

Initial 1 2 3 4 5 6

35.2 33.7 35.2 37.0 34.5 30.5 29.5

7 . 1 3 1 .7 7.0 7.5 32.5 7 . 1 6.9 33.5 6.8 6.8 35.0 7.0 6.8 34.0 6.9 6.5 30.7 6.8 6.7 30.0 6.5

39.8 7.5 30.8 7.2 41 .5 6.8 37.2 6.9 33.0 7.3 37.4 5 .7 35.2 6.5 33. 1 7.0 34.8 5.5 36. 1 6.4 34.8 6.9 36.7 5.5 35.0 6.5 33.7 6.8 34.5 5 .4 3 1 . 1 6.9 30.8 6.7 3 1 .7 5.5 29.9 6.7 30.0 6.4 29.8 5.5

Set II

Initial 1 2 3 4 5 6

39.9 38.8 37. 1 35.3 32.7 3 1 .2 3 1 .8

7.4 39. 1 7.2 43.5 6.9 40. 1 7 . 1 37.5 6.8 33.0 6.6 30.8 6.4 30.7

T= Temperature; Values represented % by weight.

7.2 5.9 6. 1 5.9 5.7 5.6 5.5

first increased and then subsequently decreased in set I and continuously increased in set II, with a solitary exception of neem leaf treated baga&se, indicated that neem leaf dust is rather potent preservative. Normally, the reduction of soluble content too for increasing bacteriallfungal load in bagasse is expected

Effect of preservatives on temperature and pH profiles

By and large reducing trend in temperature and limited reduction in pH (Table 6) indicated that the

39.5 7 . 1 39.6 7.4 42.9 6. 1 42.7 5.8 39.7 6.0 40.3 5.7 38.2 5.7 37.7 5 .8 32.7 5.8 3 1 .8 5.5 30.2 5 .7 3 1 .7 5.4 30. 1 5.6 3 1 .0 5.4

treatments were relatively equally effective in arresting the microbial growth, which alone could raise temperature due to multiplication and concomitantly reduce pH by the consumption of reducing sugars and other solubles by their transformation in to organic acids.

Suitability of bagasse after preservation A question is logically raised as to whether

minimum values of different properties mentioned acceptable in paper industry ? Generally, bagasse is

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used after de-pithing and hence degradation of pith does not affect acceptability of fibre for pulping. Percentage of cellulose and hemicelluose is crucial for industrial acceptability as they are prime contributors to quality and yield of pulp. Their reduction from 64.4% to 6 1 .6% appears acceptable as only a few paper mills use bagasse as a sole source of fibre, while majority users supplement bagasse between 1 0-25% in bamboo or eucalyptus pulp as a measure for economization. In practice, degradation of fibre leads to decrease in strength of paper, which is of little relevance for routine applications, while for value added applications, use of bagasse is not considered at all. Reduced values of reducing sugars, lignin, solubles, pH and temperature have absolutely no effect on the acceptability of preserved bagasse. Finally, bacteriaVfungal count affected acceptability to a limited extent as they contributed to reduction in brightness of pulp/paper. In the ultimate analysis, to what extent reduced values are acceptable, remains a safe-guarded industrial secret.

Conclusion From the foregoing results, it can be concluded that

among the preservatives studied, (i) neem leaf powder has individually provided maximum preservative effect and (ii) bagasse pre-incubated with L. delbruckii and subsequently treated with neem leaf powder has shown synergistic preservative effect.

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These findings have shown promise of expanding these studies further on large-scale. By using natural anti-microbial agents, the strategy provides desired safety for environment, by virtue of their no harmful effect during application and biodegradable nature in the long run.

Acknowledgement The authors express gratitude to the Hon'able Vice­

Chancellor, North Maharashatra University, Jalgaon and Mr. KVSS Sairam, Chairman and Managing Director, Prathista Industries Limited, Secunderabad (A.P.) for providing experimental facilities and encouragement.

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