Continuous production of oligodextrans via controlled hydrolysis of dextran in an enzyme membrane reactor

The continuous production of oligodextrans was investigated via the enzymatic hydrolysis of industrial grade dextran using an endodextranase. A recycle continuous stirred tank (CSTR) membrane reactor system was employed to provide the means of controlling oligodextran physicochemical characteristics. Response surface methodology (RSM) and a central composite statistical experimental design were used to assess the effects of substrate concentration (20 to 50 g dm(3)), enzyme concentration (6250 to 62500 U dm(3)), and residence time (60 to 120 min) in the reactor on the yield, dextrose equivalent (DE), and oligosaccharide content of the products. The reactor system was operated at steady state, generally obtained within 60 to 120 min from reactor start-up. Oligodextran yields ranged from 84.4% to 98.7%, DE values ranged from 22 to 41, and oligosaccharide content ranged from 55.9% to 93.4 % (w w(-1)). The reactor produced 3 types of oligodextran products, with respect to their polysaccharide content: (a) <15%, (b) 15% to 30%, and (c) > 30% and < 44%. Oligodextran molecular weight distributions were mainly within the molecular weight cut-off (MWCO) of 10 kDa of the membrane used.