Production of high degree polymerized chitooligosaccharides in a membrane reactor using purified chitosanase from Bacillus cereus

Crude chitosanase from Bacillus cereus NTU-FC-4 was separated by a cation exchanger to three fractions named CBCI, CBCII, and CBCIII. The CBCI hydrolyzed chitosan to yield dinners. The primary hydrolytic products of CBCII were low degree polymerized (DP) chitooligosaccharides. The CBCIII had the fastest reaction rate and yielded high DIP chitooligosaccharides (heptamer and higher DP oligomers). When CBCIII was used in the ultrafiltration membrane reactor with enzyme/substrate ratio 0.06 unit/mg and 100 min of residence time (RT), the concentration of high DP oligomers was 9.78 mg/mL which occupied ca. 48% of total oligomers in the final product as compared to ca. 29% resulted from the crude enzyme. Decrease of RT to 50 min and 33 min, the high DIP oligomers in the products were ca. 61% and 69%, respectively. This system could be operated for at least 24 h and kept a constant permeate flux and product output rate. (C) 2009 Elsevier Ltd. All rights reserved.