Fermentation by Wickerhamomyces anomalus Improved Production Yield of Fructooligosaccharides Through Transglycosidation of β-Fructofuranosidase

Fructooligosaccharides (FOS), an important prebiotic, are widely used in the food industry. β-Fructofuranosidases are commonly used for FOS production with yield of 55~60% (crude FOS syrup). The by-products glucose and fructose are produced during enzymatic conversion of FOS. Thus, the strategy for FOS production with high content (higher than 95%) has long been a topic of concern. In this study, a novel yeast <i>Wickerhamomyces anomalus</i> CAU331 was isolated from <i>Daqu</i> and applied for fermentation of crude FOS syrup. Impurities of glucose and fructose in the syrup were metabolized, which yielded a FOS content of 87.6%. Subsequently, the β-fructofuranosidase (AnFTase70) was added and synergistically worked with <i>W. anomalus</i> CAU331. A maximum FOS content of 95.1% with a concentration of 288.1 g/L and productivity of 6.26 g/L/h was obtained through the sequential action of β-fructofuranosidase and <i>W. anomalus</i> CAU331 in a 200 L fermenter. Moreover, the FOS components were composed of 19.2 g/L 1-kestose (GF₂), 127.8 g/L nystose (GF₃), 115.8 g/L 1F-fructofuranosylnystose (GF₄), and 25.5 g/L kestohexaose (GF₅). The findings gained in this study might provide a cost-effective approach for the production of FOS with high purity and expand their applications as functional food materials.