Biosynthesis of cyclodextrin glucosyltransferase and β-cyclodextrin by Bacillus macerans 314 and properties of the crude enzyme

摘要

Production of cyclodextrin glucosyltransferase (CGTase) enzymes by six bacterial cultures was investigated. Enzyme production was better in shaken than in surface cultures. Bacillus macerans 314 and B. amyloliquifaciens cultured on potato dextrose (PD) medium were the most potent strains used. The former strain which produced β-cyclodextrin (β-CD) was chosen for further studies. Addition of corn-steep liquor to PD medium afforded the maximal CD yield; nevertheless, it was α-CD instead of β-CD. Starch addition directed the organism to produce a mixture of α- and β-CD. 5% (by volume) inoculum, 72 h incubation period and 37℃ were the most applicable and led to maximal productivity of CGTase by B. macerans 314 cultured on PD medium supplemented with 0.3% CaCl_2. The lyophilized crude CGTase exhibited maximal activity at an enzyme concentration of 1.65 mg ml~(-1), 2% soluble starch, 60℃ and pH of 6.