Chitinase Production in a Fed-batch Fermentation of Colloidal Chitin using a Mixed Culture of Vibrio harveyi and Vibrio alginolyticus

Abstract

Endochitinases convert the chitin polymer to N- Acetyl glucosamine (GlcNAc) and chitooligosaccharides (COS) by random cleavage at internal points in the chitin chain. Vibrio harveyi and V. alginolyticus showed chitinase activity on Luria- Bertani chitin agar (LBC) containing 2% colloidal chitin at 26°C and 37°C and at pH 5.0, 7.0 and 9.0. V. alginolyticus showed higher and more specific chemotaxis than V. harveyi towards COS. When grown individually, chitinase production was detected by the end of 1st day of incubation in V. alginolyticus (134 U L-1), whereas in V. harveyi production was lower (84 U L-1) and detected later (2nd day). The fed-batch fermentation of colloidal chitin (4L of LBC broth) performed in a 10L Biostat® B plus bioreactor using a mixed culture of Vibrio harveyi and Vibrio alginolyticus with daily addition of 2% colloidal chitin (w/v), constant temperature (30°C), dissolved oxygen 20% and agitation 150 rpm, yielded a product with 990 units of chitinase and a specific activity of 1.250 U mg-1 by the end of three days of fermentation. The concentration of fer- mented product reduced to 10% of the original volume using a tangential flow concentrator within 30 min, led to a 3 fold increase in specific activity but a 54% decrease in total chitinase activity.