Faculty Publications

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Subject: search.filters.subject.Biocatalysis

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    Bioreduction of a drug intermediate in presence of hexane and surfactants
    (Chemical Publishing Co., 2011) Priyadarshini, S.R.B.; Mugeraya, G.; Sandhyavali, M.S.
    Enhancing the dispersion and dissolution of substrate particles in substrate/water suspension is a feasible way to improve enzyme substrate contact. The aim of the present study is to investigate the effects of organic solvents like hexane and surfactants like sodium lauryl sulphate (SLS) and cetyltrimethyl ammonium bromide (CTAB) on bioreduction of 3-[5-[(4-flurophenyl)- 1,5, di-oxopentol]-yl]-4-(s)- phenyloxazolidin-2-one using Sacchromyces cerevisiae as biocatalyst. Effect of variations in the ratio of hexane to water and the concentration of an anionic and cationic surfactants, were studied to see their effect on the bioreduction of the above mentioned ketone. As the substrate is hydrophobic, the bioreduction was tried in a biphasic system using solvent like hexane. The overall yield of the alcohol decreased significantly when the reaction was carried out in presence of hexane as compared to aqueous medium. The yield of alcohol increased when the ratio of hexane to water was 2:1, but decreased significantly with further increase in hexane concentration. The use of surfactants has been reported extensively in microbial biotransformation reactions. Hence the effect of both anionic (sodium lauryl sulphate) and cationic (cetyltrimethyl ammonium bromide) surfactants on the above said bioreduction was considered for the study. The results showed that cetyltrimethyl ammonium bromide has insignificant effect in bringing about ketone reduction while sodium lauryl sulphate exhibited three fold increase in the yield.
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    Production of propyl gallate in nonaqueous medium using cell-associated tannase of Bacillus massiliensis: Effect of various parameters and statistical optimization
    (2013) Aithal, M.; Belur, P.D.
    Enzymatic synthesis of propyl gallate in an organic solvent was studied using cell-associated tannase (E.C. 3.1.1.20) of Bacillus massiliensis. Lyophilized biomass showing tannase activity was used as a biocatalyst. The influence of buffer pH and strength, water activity, temperature, biocatalyst loading, gallic acid concentration, and 1-propanol concentration was studied by the one-factor-at-a-time method. Subsequently, response surface methodology was applied based on a central composite design to determine the effects of three independent variables (biocatalyst loading, gallic acid concentration, and 1-propanol concentration) and their mutual interactions. A total of 20 experiments were conducted, and a statistical model was developed, which predicted the maximum propyl gallate yield of 20.28 ?g/mL in the reaction mixture comprising 40.4 mg biocatalyst, 0.4 mM gallic acid, and 6.52 % (v/v) 1-propanol in 9.5 mL benzene at 30°C. The subsequent verification experiments established the validity of the model. Under optimal conditions, 25% conversion of gallic acid to propyl gallate was achieved on a molar basis. The absence of the need for enzyme purification and subsequent immobilization steps and good conversion efficiency makes this enzyme system an interesting one. Reports on the applications of bacterial whole cell systems for synthetic reactions in organic solvents are scarce, and perhaps this is the first report on bacterial cell-associated tannase-mediated esterification in a nonaqueous medium. © 2013 International Union of Biochemistry and Molecular Biology, Inc.
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    Enhancement of propyl gallate yield in nonaqueous medium using novel cell-associated tannase of bacillus massiliensis
    (2013) Aithal, M.; Belur, P.D.
    Enzymatic synthesis of propyl gallate in organic solvent was studied using cell-associated tannase (EC 3.1.1.20) of Bacillus massiliensis. Lyophilized biomass showing tannase activity was used as the biocatalyst. The effects of solvent, surfactant treatment, and bioimprinting on the propyl gallate synthesis were studied and subsequently optimized. Among various solvents, benzene followed by hexane was found to be the most favorable. Treatment of the biocatalyst with Triton X-100 at a lower concentration (0.2% w/v), before lyophilization, increased the propyl gallate yield by 24.5% compared to the untreated biocatalyst. The biocatalyst was imprinted with various concentrations of gallic acid and tannic acid. Biocatalyst imprinted with tannic acid showed 50% enhancement in the propyl gallate yield compared to the non-imprinted biocatalyst. © 2013 Taylor & Francis Group, LLC.