title: Asymmetric reduction of a ketone by wet and lyophilized cells of Geotrichum candidum in organic solvents.
abstract: Sixteen organic co-solvents were screened for stereoselective reduction of 1-acetonapthone in aqueous media by whole cells of Geotrichum candidum. Benzyl alcohol was found to be a good co-solvent as it afforded a high coversion and reduced deactivation of the cells. Half-lives of the wet and lyophilized whole cell biocatalysts in pure benzyl alcohol were 23.07 and 11.21 hours, respectively. The initial reaction rates at 30°C were 13.1 and 11.0μmol/min, respectively, for the wet and lyophilized cells. With optimized conditions in a reaction medium containing phosphate buffer and benzyl alcohol (1:1 by vol) with 230mM 1-acetonapthone, more than 98% and 81% conversion (ee >99%) was achieved in 5 hours with the wet and lyophilized cells, respectively. Both the cell preparations showed maximum conversion at 30°C. A thermodynamic characterization revealed that the wet cells were more thermostable than the lyophilized cells. The calculated half-life of the wet cells at pH 7 was 93 hours, whereas that of the lyophilized cells was 71 hours at the same condition.
authors.affiliation: Department of Pharmaceutical Technology (Biotechnology), National Institute of Pharmaceutical Education and Research, Sector-67, S.A.S. Nagar-160 062, Punjab, India.
authors.forename: Mani Shankar
authors.initials: MS
authors.lastname: Bhattacharyya
authors.forename: Amit
authors.initials: A
authors.lastname: Singh
authors.forename: Uttam Chand
authors.initials: UC
authors.lastname: Banerjee
mesh_terms: D019905:Benzyl Alcohol / Q000737:chemistry*; D002384:Catalysis; D005612:Freeze Drying; D005848:Geotrichum / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007659:Ketones / Q000737:chemistry*; D009281:Naphthalenes / Q000737:chemistry*; D010084:Oxidation-Reduction; D013816:Thermodynamics
chemical_list: D007659:Ketones; D009281:Naphthalenes; D019905:Benzyl Alcohol; C521160:1-acetonaphthone