Whole-cell catalytic synthesis of 2-O-α-glucopyranosyl-l-ascorbic acid by sucrose phosphorylase from Bifidobacterium breve via a batch-feeding strategy

Abstract

l-ascorbic acid 2-O-α-d-glucoside (AA-2G), a highly stabilized vitamin C derivative, has been widely applied in cosmetics, foods, and pharmaceuticals. Sucrose phosphorylase (SPase) was recently reported to be effective for producing AA-2G. In this study, SPase from Bifidobacterium breve (BbrSPase) was identified as a new AA-glycosylating tool with high activity and good thermostability. The optimal conditions for AA glycosylation are pH 5.5 and 55 °C. The Km and kcat when sucrose was applied as a glycosyl donor were 2.72 ± 0.49 mM and 9.70 ± 0.10 s−1, respectively. The transglycosylation activity was seriously inhibited by fructose, which caused a sharp decline in the glycosylation rate but did not necessarily stop the yield of AA-2G due to the high affinity to sucrose. Therefore, to attenuate the inhibition of fructose, a new sucrose batch-feeding strategy was developed for the effective production of AA-2G. The maximum titer was 185 g/L within 72 h. The molar conversion rate of l-AA reached 50.2 %, which is the highest conversion rate to our knowledge.