Abstract
Quercetin is an essential ingredient in functional foods and nutritional supplements, as well as a promising therapeutic reagent. Also, the green technique to produce quercetin via rutin biotransformation is attractive. Genes encoding two thermostable glycosidases from Dictyoglomus thermophilum were cloned and expressed in Escherichia coli, which were applied in rutin biotransformation to produce highly pure quercetin at a high temperature. The production of biocatalysts were scaled up in a 5-L bioreactor, yielding a several-fold increase in total enzyme activity and a quercetin production of 14.22 ± 0.26 g/L from 30 g/L of rutin. Feeding strategies were optimized to boost biomass and enzyme production, achieving an activity of 104,801.80 ± 161.99 U/L for rhamnosidase and 12,637.23 ± 17.94 U/L for glucosidase, and a quercetin yield of 20.24 ± 0.27 g/L from the complete conversion of rutin. This study proposes a promising approach for producing high-quality quercetin in an industrial setting.