Periconia hispidula A New Semiarid Biocatalyst for the Reduction of Prochiral Aromatic Ketone

The ability of fungus Periconia hispidula (42/07), isolated at the semi-arid of BAHIA in Brazil, to biotransform acetophenone and its derivatives has been studied. The influence of reaction parameters (mean, time, amount of substrate) on the conversion and enantioselectivity of acetophenone reduction was initially investigated. By comparison between culture media (optimized YM / BD / BD supplemented with Fe2+) BD medium supplemented with Fe2+ (0.02 g/L) was selected. From the growth curve, the incubation time prior to addition of substrate (4 and 7 days) was determined. The best conversion results for obtaining the (S)-1-phenylethanol, with enantiomeric excess of 98% were reached after four days of previous incubation of the microorganism. The influence of the amount of acetophenone (20 μL to 200 μL) was also analyzed with the objective of evaluating the toxicity of the substrate. Substrate amounts greater than 100 (0.1%) were found to have resulted in conversion and enantioselectivity dropping. The biocatalyst was also tested against 20 prochiral ketones: 2-, 3- and 4-nitroacetophenone; 2-, 3- and 4- methylacetophenone; 2-, 3- and 4-methoxyacetophenone; 2-, 3- and 4-bromoacetophenone; 2-, 3- and 4- fluoracetophenone; 2,4-dimethylacetophenone; 2,5-dimethylacetophenone and 4-ethylacetophenone. Conversions of chiral alcohols ranged from 56% to 99% with enantiomeric excesses of 54 to over 99%, demonstrating that the fungus Periconia hispidula is a promising stereoselective biocatalyst for application in reduction processes of carbonyl compounds.