Biotransformations fungi

Enzyme-mediated chiral sulfoxidation has been reviewed comprehensively in historical context [188-191]. The biotransformation can be mediated by cytochrome P-450 and flavin-dependent MOs, peroxidases, and haloperoxidases. Owing to limited stability and troublesome protein isolation, a majority of biotransformations were reported using whole-cells or crude preparations. In particular, fungi have been identified as valuable sources of such biocatalysts and the catalytic entities have not been fully identified in all cases. 

The NIH shift (Daly et al. 1972) with translocation of chlorine has been demonstrated during the biotransformation of 2,4-dichlorophenoxyacetate by Aspergillus niger (Figure 9.24) (Faulkner and Woodcock 1965). The NIH shift is not restricted to fungi since it has also been demonstrated with protons—though less frequently with other substituents—in prokaryotes. 

Whereas the metabolism of aromatic hydrocarbons takes place by dioxygenation, their biotransformation by yeasts and fungi is normally initiated by monooxygenation to the epoxide followed by hydrolysis to the trani-dihydrodiols. Phenols may subsequently be formed either by elimination or by nonenzymatic rearrangement of the epoxide ... 

Streptomyces griseus NRRL 8090 catalyzes a series of biotransformations of naphthalene and 2-methyl-1,4-naphthaquinone to their corresponding racemic and diastereomeric 4-hydroxy-1-tetralones (Figure 12.1). The yields of 4-hydroxy-l-tetralone obtained with S. griseus are much higher than those produced by various fungi that oxidize naphthalene. ... 

The biotransformation of (/f,5)-Iinalool by fungi is a useful method for the preparation of natural linalool oxides. The stereospecific conversion of (J ,5)-linalool by Corynespora cassiicola DSM 62475 led to 5/f-configured furanoid linalool oxides and 55-configured pyranoid linalool oxides, both via bS -configured epoxylinalool as postulated intermediate (Figure 12.6). The biotransformation protocol affords an almost total conversion of the substrate with high enantioselectivities and a molar conversion yield close to 100% (Table 12.4). Pure linalool oxides are of interest for lavender notes in perfumery. ... 

In connection with our own work on the enzyme-catalysed hydrolysis of cyclohexene epoxide with various fungi we made the unexpected observation that the microorganism Corynesporia casssiicola DSM 62475 was able to interconvert the (1R,2R) and (1S,2S) enantiomers of the product, trans cyclohexan-1,2-dioI 25. As the reaction proceeded the (1R,2R) enantiomer was converted to the (1S,2S) enantiomer [20]. If the racemic trans diol 25 was incubated with the growing fungus over 5 days, optically pure (> 99 % e. e.) (1 S,2S) diol 25 could be isolated in 85% yield. Similarly biotransformation of cis (meso) cycIohexan-1,2-diol 26 yielded the (1S,2S) diol 25 in 41 % (unoptimized) yield (Scheme 11). 

Keywords Microorganisms, Fungi, Hydroxylation, Screening, Biotransformation, Metabolites, Phase 1, Phase 11, Glyco conjugates. Toxicology, Pharmacology. 

An interesting new area of work is the biotransformation of plant products to new compounds by their endophytic fungi. A known allelopathic compound, lepidimoide, was synthesized by an endophytic Colletotrichum sp. from okra Hibiscus esculentus) polysaccharide [(1 —> 4) — O — a-(D-galactopyranosyluronic acid)-(l - 2) —O — a-L-rhamopyranose]... 

The isolation of terpenes from plants entails several problems (e.g, very low concentrations). Therefore other sources of these flavour compounds are searched for microorganisms for example (especially bacteria and fungi) are used for the production of terpenoids [22]. Since terpenoids are very important flavour and fragrance compounds, the biotransformation of terpenes offers a very interesting source of novel... 

Recently, the biotransformation of (+)-pulegone and other monoterpenoid ketones, like (-)-piperitenone, (+)- and (-)-carvone, (-)-menthone and (-)-verbenone by yeasts and yeast-like fungi was also... 

In 1978 Givaudan patented a transformation of a-ionone [127] a fermentation of Botryodiplodia theobromae IFO 6469 with a-ionone (152) yielded a mixture of compounds (155 -157) with honeysuckle aroma, Fig. (31). The same fungi which efficiently biotransformed / -ionone also transformed a-ionone [128]. As observed for /1-ionone, a-ionone (152) transformations with Lasiodiplodia theobromae ATCC 28570 also suggested an oxygenase-type enzyme system to be responsible for the degradation of the molecule by loss of one C2-unit. 

Biodegradation Biological degradation rate followed a first order kinetics with t,/2 = 21.6 d by raw water microflora from River Nile, t,/2 = 13,8 d by raw water microflora + sewage (El-Dib Abou-Waly 1998) Biotransformation 4% of the selected 90 strains of micromycetes mostly isolated from soil-soil fungi, depleted 50% of chlorotoluron (100 mg/L) in 5-d experiment. (Vroumsia et al. 1996)... 

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