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Production of geranyl acetate and other acetates by direct esterification catalyzed by mycelium of Rhizopus delemar in organic solvent
No full textDry mycelium of Rhizopus delemar MIM catalyzed the formation of geranyl acetate using 110 mM geraniol and acetic acid at 55°C 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%
Microbial Biotransformations In Biphasic Systems: Formation Of (R)-2-Alkanols By Methylketone Reduction
No full textThe 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
Microbial biotransformations to obtain (R)- and (S)-2-octanol
No full textMicrobial 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
Biosynthesis of ascochitine and synthesis of its biogenetic precursors
No full text' Enzymic trap ' experiments show that the main biosynthetic pathway to ascochitine (1) involves the direct reduction of the enzyme-bound ester into aldehyde (4). Therefore the complete pathway has now been assessed. Various synthetic approaches have been tried to synthesize the precursors: the use of 1,3-dithians, of an organolithium equivalent to the Friedel-Crafts reagent, and of phase-transfer reactions allowed for a good introduction of the label
Microbial catalyzed esterification of primary and secondary alcohols in organic solvent
No full textMicrobial 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
Production of flavour esters by Rhizopus oryzae
No full textMicrobial 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)
Selective acylation of monosaccharides using microbial cells
No full textThe microbially catalyzed esterification of different monosaccharides (glucose, alkyl glucosides and fructose) was investigated. Lyophilized cells of Rhizopus delemar and Rhizopus ozyzae gave direct esterification of octanoic acid and glucose in acetonitrile furnishing 6-O-octanoylglucose. R. oryzae showed remarkable selectivity towards β-glucose which was readily acylated, while little esterification was observed with the α-anomer. The effects of substrate concentration, temperature and solvent were studied in the conversion catalyzed by R. oryzae with β-glucose: 2.5 g l-1 of monoester were obtained starting from 5 g l-1 of glucose and 50 g l-1 of octanoic acid in acetonitrile at 50°C. Interesterification was also studied. Tricaprylin proved to be a good acylating agent allowing 3.5 g l-1 of 6-O-octanoylglucose to be produced. Esterification of methyl- and octyl glucosides proceeded with interesting selectivity furnishing much higher yields with the β-alkyl substrates. R. delemar and R. oryzae also catalyzed highly regioselective acylation of fructose with octanoic acid and tricaprylin, giving mono-octanoylfructose with yields ranging from 3.1 to 4.0 g l-1.
The microbially catalyzed esterification of different monosaccharides (glucose, alkyl glucosides and fructose) was investigated. Lyophilized cells of Rhizopus delemar and Rhizopus ozyzae gave direct esterification of octanoic acid and glucose in acetonitrile furnishing 6-O-octanoylglucose. R. oryzae showed remarkable selectivity towards β-glucose which was readily acylated, while little esterification was observed with the α-anomer. The effects of substrate concentration, temperature and solvent were studied in the conversion catalyzed by R. oryzae with β-glucose: 2.5 gl-1 of monoester were obtained starting from 5 gl-1 of glucose and 50 gl-1 of octanoic acid in acetonitrile at 50°C. Interesterification was also studied. Tricaprylin proved to be a good acylating agent allowing 3.5 gl-1 of 6-O-octanoylglucose to be produced. Esterification of methyl- and octyl glucosides proceeded with interesting selectivity furnishing much higher yields with the β-alkyl substrates. R. delemar and R. oryzae also catalyzed highly regioselective acylation of fructose with octanoic acid and tricaprylin, giving mono-octanoylfructose with yields ranging from 3.1 to 4.0 gl-1
Phenylacetaldehyde by acetic acid bacteria oxidation of 2-phenylethanol
No full textThis paper reports the production of 2-phenylacetaldehyde from 2-phenylethanol by acetic bacteria. Several strains of acetic bacteria were investigated and three were found to be effective for this bioconversion. Different conditions (different C source for the microorganisms, pH, substrate concentration, cell immobilization) were tested with yields ranging from 30 to 52.6%
Determination of the enantiomeric composition of 1,2-diacylglycerols from olive oil by GC and 13C NMR spectroscopy
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