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

L-ascorbic acid 2-O-alpha-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 AAglycosylating tool with high activity and good thermostability. The optimal conditions for AA glycosylation are pH 5.5 and 55 degrees 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.

Automated summary

This study identified Bifidobacterium breve's SPase as a new AA glycosylating tool with optimal conditions. Using sucrose as the glycosyl donor, it was found that fructose seriously inhibited transglycosylation activity, but a new sucrose batch-feeding strategy was successfully developed to achieve high production of AA-2G.