An alkali substrate feeding engineering conversion platform for hesperetin 7‐O‐glucoside biosynthesis.

Summary: The poor water solubility of flavonoids has always been a bottleneck restricting industrial production and application. The key problem of water‐solubility of flavonoids was solved by establishing an alkali substrate‐feeding engineering conversion platform using recombinant rhamnosidase. The results showed that the recombinant enzyme had α‐L‐rhamnosidase activity. Using this enzyme, four kinds of flavonoids such as hesperidin (HSD) were successfully hydrolyzed to products such as hesperetin 7‐O‐glucoside (HMG). Four key enzyme reaction conditions such as temperature, pH, feed rate and substrate specificity were investigated, and the optimum process parameters of the conversion platform were obtained. That was, under the conditions of temperature 50 °C, pH 6 and feeding speed 0.5 mL min−1, HSD conversion efficiency can reach 8.65 mg min−1. In addition, the changes in enzyme protein structure during basic feeding were elucidated by circular binary chromatography (CD) and fluorescence spectrum. The platform has the advantages of low cost, simple process, green environmental protection, high conversion rate and product purity. This method laid a solid foundation for the resource utilisation of flavonoid glycosides and industrial production. [ABSTRACT FROM AUTHOR]