In situ purification and enrichment of fructo-oligosaccharides by fermentative treatment with Bacillus coagulans and selective catalysis using immobilized fructosyltransferase

[Display omitted] •Immobilization of recombinant FTase on an epoxy carrier produced enzyme-free FOS.•Immobilization prevented the hydrolysis of FOS by the FTase.•Fed-batch fermentation using Bacillus coagulans eliminated monosaccharides.•FOS purity reached 92% by combining fermentation with immobilized FTase. Fructo-oligosaccharides (FOS) are prebiotic sugar substitutes that can be produced from sucrose using fructosyltransferases (FTases). However, the economic value of this process is limited by inefficient product purification and enzyme reusability. In this study, enzyme-free FOS preparations were produced by immobilizing the FTase on resin carriers. This also increased the catalytic selectivity of the enzyme. However, the crude FOS preparations still contained high concentrations of monosaccharide byproducts and residual disaccharides that must be removed because they lack prebiotic activity. A hybrid process was developed in which fed-batch fermentation was combined with the probiotic bacterium Bacillus coagulans (which selectively utilizes monosaccharides) and the simultaneous conversion of residual sucrose using the FTase to increase FOS purity. This process depleted the monosaccharides and increased the concentration of FOS to 130–170 g·L-1. The residual sucrose was converted to FOS by the immobilized FTase, increasing the overall purity of FOS to 92.1%.