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.
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