Isolation of Cyclodextrin Producing Thermotolerant Paenibacillus sp. from Waste of Starch Factory and Some Properties of the Cyclodextrin Glycosyltransferase

A Cyclodextrin (CDs) producing bacteria was isolated from waste of starch factory in Thailand and identified as Bacillus circulans by biochemical characterization and Paenibacillus sp. by 16S rRNA. The Paenibacillus grew and produced cyclodextrin glycosyltransferase (CGTase) at temperature range 37–45 °C. The optimum culturing conditions for highest CD-forming activity were pH 10.0 and 40 °C for 72 h in Horikoshi broth containing 0.5% soluble starch. The CGTase was partially purified by starch absorption, with 64% recovery and purification fold of 27. The optimum temperatures for dextrinizing and CD-forming activity were 70 and 50–55 °C. At the optimum temperature, the optimum pH for dextrinizing activity was 6.0, while CD-forming activity was 7.0. When the enzyme was incubated for 1 h at different temperatures, CD-forming activity retained its full activity up to 70 °C while dextrinizing activity dropped to 60%. Cyclodextrin products analyzed by HPLC was α:β=1:1, temperature of reaction mixture can affect the yield of CDs.