Continuous ultrafiltration membrane reactor coupled with nanofiltration for the enzymatic synthesis and purification of galactosyl-oligosaccharides

Abstract

Continuous enzymatic production of galactosyl-oligosaccharides (GOS) from a lactose substrate in an ultrafiltration membrane reactor (UMR) coupled with a nanofiltration separation system (CPNSS) was investigated. The overall rate of production over 4h of continuous production was 80–104mg GOS formed/U with an average residence time of 66min, an initial lactose concentration of 300g/L, an inlet pressure of 2.0bar inlet pressure, and an outlet pressure of 1.5bar. In the continuous diafiltration (CD) process, the concentration of various sugars and the relationship between the yield and purity of oligosaccharides was well predicted by mathematical models, the increased rate of sugar rejections was less than 10%, and the decreased rate of concentrations in the tank was less than 15%. In the CPNSS, 33.4wt.% GOS was obtained in the UMR, and 1.24kg of high-purity GOS (specifically, GOS purity of 57.2% and lactose content less than 20%) was achieved. This final yield was 80.1% GOS, which meets industry standards.