Microbial catalyzed esterification of primary and secondary alcohols in organic solvent

Microbial esterification of primary and secondary short chain alcohols with butyric acid in organic solvent has been studied. A screening for 2-octylbutyrate hydrolysis between microorganisms belonging to different genera allowed the selection of 12 microbial strains able to hydrolyze this substrate. The potential of these microorganisms in catalyzing ester formation was checked for various 1- and 2-alkylbutyrate derivatives: Rhizopus delemar, Rhizopus oryzae and Sarcina lutea promoted both 1- and 2-alkylbutyrate synthesis with almost complete molar conversion of the primary alcohols, while Aspergillus niger and Yarrowia lipolytica only catalyzed 1-alkanol esterification

Microbial Biotransformations In Biphasic Systems: Formation Of (R)-2-Alkanols By Methylketone Reduction

The microbial enantioselective reduction of C4-C8 methylketones to the corresponding (R)-alcohols was investigated. Firstly the reduction of 2-octanone with Micrococcus luteus ATCC 9341 and Pichia etchellsii CBS 2011 was studied: these transformations afford (R)-2-octanol with incomplete enantioselectivity (enantiomeric excesses, e.e., of 80% and 50%, respectively). It was observed that stereoselectivity can be enhanced by performing the transformation in the presence of a suitable organic solvent. The presence of hydrophobic solvents avoids racemization of the alcohol formed, by continuously extracting it from the aqueous phase. The use of M. luteus and P. etchellsii in biphasic systems with n-heptane enabled the formation of (R)-2-octanol in high optical purity (> 97%). The same system was also used to carry out reductions of other methylketones with the two microorganisms. (R)-2-Alcohol formation was always observed with a high optical purity

Production of flavour esters by Rhizopus oryzae

Microbial production of different aliphatic esters with flavour characteristic has been studied. Lyophilized whole cells of Rhizopus oryzae CBS 112-07 were found to be particularly suitable to catalyse the synthesis of different flavour esters (hexyl acetate, propionate, butyrate, caprylate; geranyl acetate, propionate, butyrate and 2- and 3-methylbutyl acetate, butyrate) in n-heptane. This strain was therefore utilized for the semipreparative production of geranyl butyrate by semicontinuous and continuous addition of the substrates with satisfactory yields (144 gl-1 in 264 h and 142 gl-1 in 48 h respectively)

Microbial biotransformations to obtain (R)- and (S)-2-octanol

Microbial obtainment of (R)- and (S)-2-octanol was studied. Two strategies were developed: kinetic resolution of 2-octanol racemic mixture through selective oxidation and enantioselective reduction of 2-octanone. Two strains of acetic acid bacteria were found to preferentially oxidize (R)-2-octanol with moderate discrimination between the enantiomers. Various microorganisms belonging to different genera gave 2-octanone reduction with general preference for (S)-2-octanol formation. Lactobacillus fermentum ILC G18D, Acetobacter sp. CH MIM, Candida boidinii CBS 2428 and Pichia fermentans DPVPG 2770 afforded (S)-2-octanol with an enantiomeric excess (e.e.) greater than 97%. Reduction of shorter chain methyl ketones with Candida boidinii and Pichia fermentans showed that the ketone structure was extremely important to the transformation stereobias

Production of geranyl acetate and other acetates by direct esterification catalyzed by mycelium of Rhizopus delemar in organic solvent

Dry mycelium of Rhizopus delemar MIM catalyzed the formation of geranyl acetate using 110 mM geraniol and acetic acid at 55\ub0C in heptane to give 11.9 g/l (55% molar conversion). Geranyl acetate was produced at 72.5-75 g/l after 10 days by semi-continuous addition of the substrates. Rhizopus delemar also catalyzed the direct acetylation of different primary alcohols with molar conversions ranging from 65 to 98%

Isolation of a novel carboxylesterase from bacillus coagulans with high enantioselectivity toward racemic esters of 1,2-O-isopropylideneglycerol

An intracellular carboxylesterase from Bacillus coagulans NCIMB 9365 with high stereospecific hydrolytic activity toward racemic esters of 1,2-O-isopropylideneglycerol was purified and characterized. The microorganism contained two intracellular carboxylesterases designated as carboxylesterase A and B. Purification was achieved in three steps: precipitation with ammonium sulfate from the crude cellular lysate, ion exchange, and gel filtration chromatography. Carboxylesterase A is stereoselective, has a molecular weight of 70\u201373 kDa with an isoelectric point of 4.7, and a maximum activity (assayed on \u3b1-naphthylcaprylate) at pH 7.0 and 65\ub0C. The enzyme showed good affinity toward (r)-benzoyl-1,2-isopropylideneglycerol (Km = 1.05 mm) and its activity on this substrate was competitively inhibited by (s)-benzoyl-1,2-isopropylideneglycerol. The purified enzyme yielded (s)-1,2-O-isopropylideneglideneglycerol with high enantiomeric excesses (e.e.) by resolution of various racemic esters (97% e.e starting from benzoate ester)