Optimization of Cyclodextrin Glycosyltransferase Production from Klebsiella pneumoniae AS-22 in Batch,Fed-Batch and Continuous Cultures

摘要

Production of a novel cyclodextrin glycosyltransferase (CGTase)from Klebsiella pneumoniae AS-22 strain,which converts starch predominantly to alpha-CD at high convesion yields,in batch,fed-batch,and continuous cultures,is presented.In tach fermentations,optimization of different operating parameters such as temperature,pH,agitation speed,and carbon-source concentration resulted in more than 6-fold increase in CGTase activity.The enzyme production was further improved by two fed-batch approaches.First,usingglucose-based feed to increase cell density,followed by starch-based feed to induce enzyme production,resulted in high cell density of 76 g dry cell weight/L,although the CGTase production was low.Using the second approach of a single dextrin-based feed,20-fold higher CGTase was produced compared to that in batch fermentations with media containing tapioca starch.In continuous operation,more than 8-fold increase in volumetric CGTase productivity was obtained using dextrin-based media compared to that in batch culture using starch-based media.