Regulated preparation of crocin-1 or crocin-2' triggered by the co-solvent DMSO using Bs-GT/At-SuSy one-pot reaction.

Crocins are the primary coloring ingredients of saffron. The low-glycosylated members of this compound family, such as crocin-1(crocetin mono-glucosyl ester) and crocin-2' (crocetin di-glucosyl ester), are rarely distributed in nature and attracting interest in their therapeutic uses. In our previous studies, glucosyltransferase Bs-GT from Bacillus subtilis GT was mined for the biosynthesis of crocins from crocetin. In the present study, a one-pot reaction system was used for efficient preparation of crocins with in situ regeneration of UDP-Glc by coupling by coupling Bs-GT with a sucrose synthase, At-SuSy, from Arabidopsis thaliana. It is interesting to note that DMSO was used as a cosolvent and resulted in the improvement of the solubility of the substrate crocetin and the regulation of the selectivity of the glycosylation. With periodic addition of crocetin, the biosynthesis of crocin-2' was performed with a high yield of 3.25 g/l in 2% DMSO aqueous solution, while crocin-1 (2.12 g/l) was selectively obtained in a 10% DMSO aqueous solution. The present study provided a simple approach for the biosynthesis of crocin-1 and crocin-2' using solvent engineering.