Research review paper

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1. Introduction . . . . . . . . . . . . . .2. Production methods . . . . . . . . . .

2.1. Extraction from plants . . . . . .2.2. Fermentation processes . . . . .

pathwat and e. . . .n . . .. . . .. . . .

Biotechnology Advances 30 (2012) 14251431

Contents lists available at SciVerse ScienceDirect

Biotechnolog

j ourna l homepage: www.e lsev1. Introduction

This review is focussed on the methods of producing shikimic acid(3,4,5-trihydroxy-1-cyclohexene-1-carboxylic acid), a chemicalbuilding block for the antiviral drug oseltamivir (Tamiu). Shikimicacid is named after the Japanese shikimi (Illicium anisatum) ower

from which it was rst isolated. Shikimic acid is an intermediate ofthe shikimic acid pathway (Herrmann and Weaver, 1999) that is in-volved in the synthesis of aromatic metabolites in plants and micro-organisms (Ganem, 1978; Herrmann, 1995; Pittard, 1996; Wilson etal., 1998). Metabolically essential products of the shikimic acid path-way include the three aromatic amino acids L-phenylalanine,L-tryptophan and L-tyrosine. Shikimic acid pathway is not normallyassociated with animals, but genes for coding some of the enzymes

Abbreviations: DAHP, 3-Deoxy-D-arabino-heptulosonate-7-phosphate; DHQ,

3-Dehydroquinate or 3-dehydroquinic acid; DHS,dehyroshikimic acid; DQD, 3-Dehydroquinate dehydrogenmate-3-phosphate; E4P, Erythrose-4-phosphate; GDH, GNicotinamide adenine dinucleotide phosphate; NADPH, Reenine dinucleotide phosphate; PEP, Phosphoenolpyruvatenase; SKDH, Shikimic acid dehydrogenase. Corresponding author. Tel.: +91 172 2214682 87; f

E-mail address: ucbanerjee@niper.ac.in (U.C. Banerje

0734-9750/$ see front matter 2012 Elsevier Inc. Alldoi:10.1016/j.biotechadv.2012.03.001References . . . . . . . . . . . . .2.2.1. The shikimic acid2.2.2. Use of recombinan

2.3. Chemical synthesis . . .2.4. Microbial biotransformatio

3. Concluding remarks . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1425

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Available online 14 March 2012

Keywords:Shikimic acidOseltamivirQuinic acid

Shikimic acid is a key intermediate for the synthesis of the antiviral drug oseltamivir (Tamiu). Shikimicacid can be produced via chemical synthesis, microbial fermentation and extraction from certain plants. Analternative production route is via biotransformation of the more readily available quinic acid. Much of thecurrent supply of shikimic acid is sourced from the seeds of Chinese star anise (Illicium verum). Supplyfrom star anise seeds has experienced difculties and is susceptible to vagaries of weather. Star anise treetakes around six-years from planting to bear fruit, but remains productive for long. Extraction and purica-tion from seeds are expensive. Production via fermentation is increasing. Other production methods aretoo expensive, or insufciently developed. In the future, production in recombinant microorganisms via fer-mentation may become established as the preferred route. Methods for producing shikimic acid arereviewed.

2012 Elsevier Inc. All rights reserved.Production of shikimic acid

Saptarshi Ghosh a, Yusuf Chisti b, Uttam C. Banerjee a

a Department of Pharmaceutical Technology (Biotechnology), National Institute of Pharmab School of Engineering, Massey University, Private Bag 11 222, Palmerston North, New Zea3-Dehydroshikimate or 3-ase; EPSP, 5-Enolpyruvylshiki-lucose dehydrogenase; NADP,duced form of nicotinamide ad-; QDH, Quinic acid dehydroge-

ax: +91 172 2214692.e).

rights reserved.ical Education and Research, Sector-67, S.A.S. Nagar-160 062, Punjab, India

y Advances

i e r .com/ locate /b iotechadvof the pathway have been found in certain animals (Starcevic et al.,2008). Properties and toxicology of shikimic acid have been discussedelsewhere (Stavric and Stoltz, 1976). An insufciency of shikimic acidhas in the past affected the supply of oseltamivir (Farina and Brown,2006).

As a highly functionalised, six-carbon ring with three chiral car-bons and a carboxylic acid functional group, shikimic acid (Fig. 1) is

a versatile enantiomerically pure precursor for making potentiallyuseful products. Interest in shikimic acid has been rekindled as it isrequired for producing the avian u drug oseltamivir (Fig. 1). Inview of the potential impact of a u pandemic (Horimoto andKawaoka, 2001) and the limited usefulness of vaccines against rapidlyevolving u viruses, stockpiles of effective drugs are necessary formanaging a major outbreak. Oseltamivir is an effective treatmentfor inuenza (Widmer et al., 2010), especially if administered early.Oseltamivir is effective against both Type A and Type B inuenzaand it is used also in prophylaxis.

Oseltamivir is a viral neuraminidase inhibitor. Its synthesis fromquinic acid via shikimic acid has been described (Kim et al., 1997,1998; Rohloff et al., 1998). Oseltamivir produced for early clinical trialshad been made from chemically synthesized shikimic acid (Federspielet al., 2001), but this method proved impractical for commercial pro-duction of the drug. Chemical and microbial methods for inexpensiveproduction of shikimic acid are being developed, but most of thiscompound is currently extracted from the seeds of Chinese staranise (Illicium verum) (Payne and Edmonds, 2005). The multistep

extraction and purication processes are expensive. Use of recombi-nant bacteria for commercial production of shikimic acid is develop-ing. Newer routes for producing oseltamivir without the use ofshikimic or quinic acids have appeared (Fukuta et al., 2006; Yeunget al., 2006), but not been commercialized. Herewe review the existingand emerging methods for producing shikimic acid.

2. Production methods

2.1. Extraction from plants

As an intermediate of the shikimic acid pathway, shikimic acidis found widely in plants (Bohm, 1965; Dell and Frost, 1993;Gurib-Fakim, 2006; Herrmann and Weaver, 1999), but generally oc-curs in low concentration. Seeds of Chinese star anise (Illicium verum)are the main commercial source of shikimic acid. The botany and phar-macology of Chinese star anise have been reviewed (Wang et al., 2011).

Shikimic acid was rst isolated from owers of the highly toxicJapanese star anise. Subsequently, it was reported in the leaves ofthe sweetgum tree (Liquidambar styraciua) (Plouvier, 1961). Theseeds of the American sweetgum tree have been found to containup to 3.7% (w/w) shikimic acid (Enrich et al., 2008). Extraction of shi-kimic acid from bark and wood of the sweetgum has been reported(Martin et al., 2010). A simple extraction method based on hotwater was used. Several varieties of pine, r and spruce are knownto produce shikimic acid. A hot water (4575 C) extraction of theneedles of Scots pine (Pinus sylvestris) yielded around 1.6% (w/w)shikimic acid (Sui, 2008). Extraction from the needles of the pinePinus elliottii has been described (Xie et al., 2010). Attempts arebeing made to identify other natural plant sources of shikimic acid(Raghavendra et al., 2009).

Fig. 1. Structure of shikimic acid and oseltamivir.

1426 S. Ghosh et al. / Biotechnology Advances 30 (2012) 14251431Fig. 2. The shikimic acid or shikimate pathway.

Plants of the genus Illicium appear to the best source of shikimicacid, but many Illicium species are poisonous (Lederer et al., 2006;Yamada et al., 1968) and therefore not suitable for producing com-mercial shikimic acid. Japanese star anise (I. anisatum) is highlytoxic, but the Chinese star anise (I. verum) is edible. Nevertheless,compounds found in Chinese star anise have been shown to betoxic to infants (Ize-Ludlow et al., 2004).

Shikimic acid is highly soluble in water (180 g/L at 20 C), but notin non-polar solvents. Therefore, a hot water extraction of the planttissue is used as the primary extraction step (Ohira et al., 2009; Sui,2008; Xie et al., 2010; Ye et al., 2007). Shikimic acid content in theplant tissue varies depending on the source of the tissue, the time ofharvest and other possible factors. Roughly 1 kg of shikimic acid can

duces DHS to shikimic acid. The rate limiting enzymes of the shikimicacid pathway of E. coli are DHQ synthase and shikimate kinase (Delland Frost, 1993) (Fig. 2). Shikimate kinase (aroL and aroK) is responsiblefor converting shikimic acid to shikimate-3-phosphate (Fig. 2).

In E. coli, the enzymes DHQ synthase, DHQ dehydratase andshikimate dehydrogenase (Fig. 2) are constitutively expressedwhereas the production of the DAHP synthases and one of the

Table 2Modied E. coli strains with 3-dehydroshikimic acid yield and titer (Li et al., 1999).

Number Strain Modication DHS yield(mol/mol)

DHS titer(g/L)

1 KL3/pKL4.33B

aroFFBR expression controlled byParoF in absence of amplied tktA

0.17 20.3

2 KL3/pKL4.66A

aroFFBR expression controlled byParoF in absence of amplied tktA

0.16 38.5

3 KL3/pKL4.130B

aroFFBR expression controlled byParoF in the presence of ampliedtktA

0.30 69.0

4 KL3/ aroFFBR expression is controlled 0.18 41.2

Table 3Effect of carbon sources on the production of 3-dehydroshikimic acid by recombinantE. coli strains (Li et al., 1999).

Strain KL3/pKL4.124A(tktA over expression)

KL3/pKL4.79B (tktA)

Carbon source DHS titer(g/L)

DHS yield(mol/mol)

Carbonsource

DHS titer(g/L)

DHS yield(mol/mol)

Glucose 46.0 0.28 Glucose 36.4 0.22Xylose 43.1 0.33 Xylose 41.7 0.32Mixa 64.0 0.41 Mixa 53.0 0.36

a

1427S. Ghosh et al. / Biotechnology Advances 30 (2012) 14251431be recovered from 30 kg of dry seed pods of Chinese star anise(Ohira et al., 2009; Roche, 2006). Recovery is nearly complete (>95%)within 10 min of water extraction at 70 C from seed pods ground to aparticle size of 355600 m (Ohira et al., 2009). The rate of recoverycan be further enhanced by using a higher extraction temperature.

Other extraction methods have been described, involving the useof acids (Harring et al., 1998; Mueller, 2003), alcohols (Anderson etal., 2001; Jaroszynska, 2003), complex formation (Miles et al., 1994;Sadaka and Garcia, 1999) and microwave-assisted extraction(Matallo et al., 2009). The crude water extract contains numerousother water-soluble plant metabolites and requires extensive furtherprocessing to yield pure shikimic acid. The recovery and puricationprocesses used in commercial production from Chinese star aniseare proprietary and involve multiple steps.

2.2. Fermentation processes

Microbial production of shikimic acid involves the shikimic acid (orshikimate) pathway. Shikimic acid pathway occurs commonly inmicro-organisms and therefore they can be used to overproduce this com-pound from carbon sources such as glucose (Draths et al., 1999;Simonart and Wiaux, 1960). Shikimic acid is a precursor for essentialamino acids and other metabolites in microorganisms. Its overproduc-tion can be achieved for example by metabolic engineering to partlyblock some of the biochemical pathways that consume shikimic acidand by overexpression of the enzymes responsible for its synthesis. Pro-duction by fermentation using engineered microorganisms is alreadysupplementing the commercial supply of shikimic acid.

2.2.1. The shikimic acid pathwayThe shikimic acid pathway is shown in Fig. 2. Thismetabolic pathway

is used to produce the aromatic amino acids that are essential to growth.Shikimic acid is an intermediate in the pathway. This pathway has beenpreviously reviewed (Herrmann andWeaver, 1999).

The shikimic acid pathway begins with phosphoenolpyruvate(PEP) and erythrose-4-phosphate (E4P) (Fig. 2). These two com-pounds must rst be generated from metabolism of glucose, orother carbohydrate. PEP is produced through the glycolysis pathway(Fig. 2) whereas the completely independent pentose phosphate

Table 1Modied E.coli strains with shikimic acid (SA) yield and titer.

Strain Modication SA yield(mol/mol)

SAtiter (g/L)

SP1.1/pKD15.071B(Chandran et al., 2003)

Over expression of ppsA 0.23 66

SP1.1pts/pSC6.090B(Chandran et al., 2003)

PTS/glf+/tktA overexpression

0.27 71

SP1.1/pKD12.138(Knop et al., 2001)

Over expression of tktA 0.18 52

SP1.1/pKD12.112(Draths et al., 1999)

Insertion of aroB into theserA locus of E.coli anddisruption of aroL and aroK

0.15 27.2pathway is used to generate E4P (Fig. 2). Thus, the shikimic acid path-way is dependent on the glycolytic pathway and the pentose phos-phate pathway to provide the two starting materials it requires.Therefore, metabolic engineering of the shikimic acid pathway alonemay be insufcient for increasing the yield of shikimic acid from thecarbon source used in a fermentation. Furthermore, because shikimicacid is produced far downstream in the metabolic pathway relative tothe point where glucose rst enters the metabolism, channelling theow of carbon to production of shikimic acid can be difcult.

Once E4P and PEP have been generated through carbohydrate me-tabolism in other independent pathways, they are condensed in theshikimic acid pathway through the action of the enzyme DAHPsynthase to produce DAHP. Action of three other enzymes then con-verts DAHP to shikimic acid. Chorismic acid is the nal product ofthe SA pathway and this compound is the common precursor forthe biosynthesis of other aromatic products such as aromatic aminoacids, as it is shown in Fig. 2.

The shikimic acid pathway engineering has most commonly in-volved the bacterium Escherichia coli. This microorganism has threeisoforms of the DAHP synthase enzyme encoded by aroF, aroG, aroHshow feedback inhibition by the three aromatic amino acids, i.e.L-tyrosine, L-phenylalanine and L-tryptophan respectively. TheDAHP synthase (aroG) of Bacillus subtilis is inhibited by the pathwayintermediate chorismate (Jensen and Nester, 1966a,b) (Fig. 2).

The enzyme DHQ synthase (aroB) in E. coli converts DAHP into3-dehydroquinate (DHQ). The enzyme DHQ dehydratase (aroD) thenconverts DHQ into 3-dehydroshikimate (DHS) by eliminating water.Subsequently, NADPH-dependent shikimate dehydrogenase (aroE) re-

pKD11.291A by ParoF in absence of ampliedtktA

5 KL3/pKL5.17A

aroFFBR expression is controlledby ParoF in presence of ampliedtktA

0.24 58.1

6 KL3/pKL4.124A

aroFFBR expression under thecontrol of Ptac in presence of tktA

0.28 66.0Molar ratio of glucose/xylose/arabinose: 3:3:2.

Fig. 3. Synthesis of shikimic acid via Diels-Alder reaction (McCrindle et al., 1960; Smissman et al., 1959). Based on Ambhaikar (2005).

1428 S. Ghosh et al. / Biotechnology Advances 30 (2012) 14251431shikimate kinases is transcriptionally regulated. Shikimic acid in-hibits shikimate dehydrogenase (Dell and Frost, 1993).

An alternative microbial route to shikimic acid is through bio-transformation of quinic acid. Certain microorganisms (Pseudomonas,Achromobacter, Aspergillus and Neurospora crassa) can use quinic acid(or its salt, quinate) as the sole carbon source (Case et al., 1978; DaSilva et al., 1986; Rogoff, 1958) to produce aromatic amino acids viathe shikimic acid pathway. Quinate enters the pathway at the pointshown in Fig. 2. E. coli strains specically engineered for overprodu-cing quinic acid from glucose have also been developed (Ran et al.,2001).

2.2.2. Use of recombinant and engineered strainsMetabolically engineered bacteria provide an important emerging

route to production of shikimic acid via fermentation (Campbell et al.,1993; Krmer et al., 2003). The bacterium E. coli has been the focus ofmost metabolic engineering effort (Ahn et al., 2008; Escalante et al.,2010; Johansson and Liden, 2006; Johansson et al., 2005, 2006;Knop et al., 2001; Yi et al., 2002, 2003), but studies in other bacteriahave also been reported.

Several metabolic engineering approaches have been developed tooverproduce shikimic acid in E. coli (Ahn et al., 2008; Chandran et al.,2003; Escalante et al., 2010; Gibson et al., 2001; Johansson et al.,2005; Knop et al., 2001; Krmer et al., 2003). All these are based ongenetic modications to alter the central carbon metabolism andthe shikimic acid pathway (Table 1).

The shikimic acid pathway requires PEP and E4P (Fig. 2). The sup-ply of PEP and E4P can be enhanced via metabolic engineering of theglycolytic pathway and the pentose phosphate pathway, respectively.Both these approaches have been demonstrated. Over expression oftransketolase (tktA) resulted in the increase of shikimic acid yieldfrom 0.12 to 0.18 mol/mol and titer from 38 to 52 g/L by enhancingthe concentration of E4P (Knop et al., 2001). In recombinant E. coli,Fig. 4. Shikimic acid synthesis of Koreeda and Ciufolian increased availability of PEP has enhanced production of shikimicacid (Chandran et al., 2003; Yi et al., 2002). The modication of theglycolytic pathway involved over expression of PEP synthase (ppsA)leading to increased shikimic acid titer to 66 g/L and yield on glucoseof 0.23 mol/mol (Chandran et al., 2003). Inactivation of the PTS operon(PTS), expression of non-PTS glucose transporters like glucose facilita-tors (glf), glucokinase (glk) in combinationwith over expression of tktAgene was reported to increase the shikimic acid titer to 71 g/L(Chandran et al., 2003; Gibson et al., 2001). Using the engineered E.coli strain, the shikimic acid concentration could be further raised to84 g/L by supplementing the minimal medium with yeast extract(Chandran et al., 2003). Shikimic acid could be produced during expo-nential growth on glucose to a nal concentration of 87 g/L (Chandranet al., 2003). The nature of the carbon source affected the productivityof shikimic acid (Ahn et al., 2008; Li et al., 1999).

In earlier studies, the shikimic acid titers from metabolically engi-neered E. coli strains were low partly due to simultaneous productionof quinic acid (Knop et al., 2001). Production of quinic acid during bio-synthesis of shikimic acid is a consequence of the microbe-catalyzedequilibration of the initially synthesized shikimic acid (Knop et al.,2001). This problem appears to have been resolved in view of the afore-mentioned high titers.

Shikimic acid can be produced readily from DHS (Fig. 2). There-fore, some metabolic engineering studies have focussed on overpro-duction of DHS. Substantial overproduction of DHS in metabolicallyengineered microorganisms has been achieved (Draths and Frost,1990; Li and Frost, 1999; Li et al., 1999; Yi et al., 2002, 2003)(Table 2). For example, E. coli constructs have produced as much as60 g/L DHS from glucose in 60 h (Yi et al., 2003). A comparative analysisof D-xylose, D-glucose and D-arabinose as carbon source for microbialsynthesis of DHSwas also reported (Li and Frost, 1999) (Table 3). Differ-ent recombinant E. coli strains were used with various carbon sourcesfor DHS production.ni (1982) as summarized by Ambhaikar (2005).

nate supplied in the medium could be converted to DHQ (Adachi et al.,

Fig. 5. Chemical conversion of ()-Quinic acid to ()-Shikimic acid (Dangschat and Fischer, 1938, 1950). Based on Ambhaikar (2005).

1429S. Ghosh et al. / Biotechnology Advances 30 (2012) 14251431The activity of DAHP synthase (Fig. 2) controls the amount of cel-lular carbon directed into DHS synthesis. Transcriptional repressionand feedback inhibition of DAHP synthase by aromatic amino acidsare believed to control the activity of this enzyme. The ampliedexpression of a mutant DAHP synthase, which is insensitive tofeedback inhibition by aromatic amino acids, has been used to en-hance production of DHS. Metabolic engineering approaches havebeen employed to produce shikimic acid in E. coli strains derivedfrom an evolved strain PB 12 lacking the PTS system but with abilityto grow on glucose. The double aroK-, aroL- mutant of strain PB12.SA22 showed shikimic acid titer of 7 g/L and yield of 0.29 mol/mol(Escalante et al., 2010).

In addition to recombinant E. coli, genetically modied or other-wise mutated Bacillus subtilis (Iomantas et al., 2002) and Citrobacterfreundii bacteria (Shirai et al., 2001) have been used to successfullyoverproduce shikimic acid although the titers have not exceededabout 20 g/L. It was reported that aroI (shikimate kinase) decientstrain of B. subtilis showed shikimic acid titer of 8.5 g/L with hightiter of DHS (9.5 g/L) as the by-product (Iomantas et al., 2002). Useof glyphosate, an inhibitor of the enzyme EPSP synthase (Fig. 2), inthe fermentation medium to enhance accumulation of shikimic acidby blocking its downstream consumption, has been described(Bogosian, 2011). Metabolic engineering of microorganisms for pro-ducing shikimic acid has been reviewed by Krmer et al. (2003).

2.3. Chemical synthesis

Chemical synthesis of shikimic acid was rst achieved during the1960s using the basic chemistry of Diels-Alder reaction (Fig. 3) toform six membered rings (McCrindle et al., 1960; Smissman et al.,1959), but the yield was low at 15%. Later attempts to increaseyield were not particularly successful (Grewe and Hinrichs, 1964).In 1982, the efciency of Diels-Alder synthesis could be improved(Fig. 4) to raise the yield to 29% (Koreeda and Ciufolini, 1982). Amore efcient synthesis further raised the yield to 55% (Koreeda etal., 1990).

Synthesis of shikimic acid from benzene has been shown to bepossible (Birch et al., 1988). Synthesis via a palladiummediated elim-ination reaction was advanced by Yoshida and Ogasawara (2000).Synthesis of ()-shikimic acid has been reported from sugars suchas D-mannose (Dangschat and Fischer, 1938, 1950; Fleet et al., 1984;Jiang et al., 1994). Shikimic acid can be made also from ()-quinicacid and its derivatives by chemical transformations (Box et al., 2002;Cleophax et al., 1971, 1973; Federspiel et al., 2001; Kim et al., 1997,1998; Rohloff et al., 1998) (Fig. 5). Other synthetic methods haveFig. 6. Synthesis of oseltam2003). This transformation could be achieved also with dried cells ofG. oxydans (Adachi et al., 2003) and with fresh cells immobilized inalginate beads. The intermediate DHQ could be further transformedto DHS in a reasonable yield by both growing and immobilizedcells. Lactobacillus pastorianus is capable of converting quinic acid to aproduct that was claimed to be dihydroshikimic acid (Carr et al.,1957), but was more likely DHS.

A two-step scheme for biotransformation of quinic acid to shikimicacid has been published (Fig. 7) (Adachi et al., 2006). The rst step ofthis scheme involves an oxidative fermentation with G. oxydans to es-sentially quantitatively convert quinic acid in the culture medium toDHS. The latter is subsequently converted to shikimic acid in anNADPH-dependent reaction using the enzyme shikimic acid dehy-drogenase (SKDH) (Fig. 7) puried from cells of G. oxydans. The en-zymatic biotransformation medium also contained glucose and theenzyme glucose dehydrogenase to continuously regenerate NADPH(Fig. 7).been described (Kancharla et al., 2009; Snchez-Abella et al., 2006).Chemical synthesis of shikimic acid and its analogs is further reviewedelsewhere (Campbell et al., 1993; Jiang and Singh, 1998).

Although several routes have been described for chemical synthesis,production of shikimic acid by these methods is too expensive to beof commercial use. Consequently, isolation from Chinese star anisefruit remains the principal source of commercial shikimic acid(Raghavendra et al., 2009).

The ten step commercial route of oseltamivir (Tamiu) synthesisuses ()-shikimic acid as the starting material (Abrecht et al., 2004).This precursor is converted into a diethyl ketal intermediate, which isreductively opened to give 1,2-epoxide. This epoxide is then con-verted into oseltamivir via a ve step reaction involving 3 potentiallytoxic and explosive azide intermediates (Fig. 6). This route gives 35%yield of oseltamivir. Future methods for making oseltamivir maycompletely circumvent the need for shikimic or quinic acids (Fukutaet al., 2006; Yeung et al., 2006).

2.4. Microbial biotransformation

Many microorganisms are able to convert quinic acid to shikimicacid (Adachi et al., 2003, 2006). Quinic acid (or quinate) is convertedto 3-dehydroquinate (DHQ) (Fig. 2) through the action of quinate de-hydrogenase. DHQ is an intermediate of the shikimic acid pathwayand is transformed to shikimic acid in a two-step process (Fig. 2).

During exponential growth of Gluconobacter oxydans, nearly all qui-ivir from shikimic acid.

pro

1430 S. Ghosh et al. / Biotechnology Advances 30 (2012) 142514313. Concluding remarks

Shikimic acid is a precursor for the synthesis of the important anti-viral drug oseltamivir. Extraction from Chinese star anise is the mainsource for shikimic acid, but fermentation processes based on the re-combinant bacterium E. coli have been shown to be a viable alternativesource. Chemical synthesis of shikimic acid is possible, but apparentlynot commercially viable. Chemical methods of making oseltamivirmay entirely circumvent the need for shikimic acids, but are not com-mercially used. Bioconversion of quinic acid to shikimic acid is anotheroption for production, but appears not to have been developed to theextent of the fermentation route from glucose.

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Production of shikimic acid1. Introduction2. Production methods2.1. Extraction from plants2.2. Fermentation processes2.2.1. The shikimic acid pathway2.2.2. Use of recombinant and engineered strains

2.3. Chemical synthesis2.4. Microbial biotransformation

3. Concluding remarksReferences