ABSTRACT
Soluble cello-oligosaccharide with 2-6 oligosaccharide units is a kind of oligosaccharide with various biological functions, which can promote the proliferation of intestinal probiotics such as Bifidobacteria and Lactobacillus paracei. Therefore, it has a regulatory effect on human intestinal microbiota. In this study, a Cc 01 strain was constructed by expressing cellodextrin phosphorylase (CDP) in Escherichia coli. By combining with a previously constructed COS 01 strain, a three-enzyme cascade reaction system based on strains COS 01 and Cc 01 was developed, which can convert glucose and sucrose into cello-oligosaccharide. After optimization, the final titer of soluble cello-oligosaccharides with 2-6 oligosaccharide units reached 97 g/L, with a purity of about 97%. It contained cellobiose (16.8 wt%), cellotriose (49.8 wt%), cellotetrose (16.4 wt%), cellopentaose (11.5 wt%) and cellohexose (5.5 wt%). When using inulin, xylo-oligosaccharide and fructooligosaccharide as the control substrate, the biomass (OD600) of Lactobacillus casei (WSH 004), Lactobacillus paracei (WSH 005) and Lactobacillus acidophilus (WSH 006) on cello-oligosaccharides was about 2 folds higher than that of the control. This study demonstrated the efficient synthesis of cello-oligosaccharides by a three-enzyme cascade reaction and demonstrated that the synthesized cello-oligosaccharides was capable of promoting intestinal microbial proliferation.