Enantioselective Conversion of Racemic Sotalol to R(-)-Sotalol by Lipase AP6

Abstract

This study was aimed at selecting suitable biocatalysts for the enantioselective conversion of racemic sotalol to R(-)-sotalol and to determine the effect of immobilization on enantiomeric purity of the product. Among the various biocatalysts used, Aspergillus niger (GUFCC5443), Cunninghamella blakesleeana (CBS133.27), Cunninghamella elegans (NCIM689), Pseudomonas putida (NCIB9494), Rhodococcus erythropolis (DSM43188), Rhizopus oryzae (NCIM1009), the enzyme lipase AP6 (triacylglycerol lipase from A. niger) demonstrated the capability for enantioselective conversion. Enantioselectivity of all the cultures was improved by immobilization, which resulted in enhanced enantiomeric purity of the product. Catalysis studies with immobilized R. erythropolis and A. niger cultures yielded good enantiomeric ratios of 55.87 and 53.34 as well as good enantiomeric excesses as 96.48 and 96.45 %, respectively. Catalysis with free lipase AP6 resulted in a product of good enantiomeric purity. This enzyme’s enantioselectivity was improved by immobilization from 11.51 to 168.49, which resulted in a product with very high enantiomeric purity of 98.82 %. Hence, the immobilized-lipase AP6 was proved to be an efficient catalyst for the enantioselective conversion of racemic sotalol to R(-)-sotalol with high enantiomeric purity followed by immobilized R. erythropolis and A. niger.