Flavonoid Glycoside Transformation Catalyzed by Whole-Cell Catalysts Using a PVDF Membrane Reactor Coupled with Reaction and Separation

Abstract

Inefficient utilization of flavonoid resources from agricultural waste has caused serious pollution of the ecological environment. Isoquercitrin, a natural and rare flavonoid, shows obvious pharmacological activities. Abandoned rutin from plant could be used to produce isoquercitrin by the employment of the rhamnose hydrolysis. This study reported an efficient preparation process of isoquercitrin using the conversion of rutin catalyzed by whole-cell catalysts in a polyvinylidene fluoride (PVDF) membrane reactor coupled with reaction and separation. The PVDF hollow fibre membrane with filtration precision of 0.1 μm was selected as the membrane module. Recombinant Escherichia coli whole cells were used as catalysts. And the effects of the extractant-substrate volume ratio, reaction temperature, pH and substrate concentration on the yield were investigated. The results showed that the isoquercitrin yield of the coupling system with an extractant increased within 0–8 h and reached a maximum yield of 82.2 ± 2.3% at 8 h. The maximum isoquercitrin yield of 87.92 ± 2.93% was obtained under the optimum reaction conditions as follows: a temperature of 40 °C, a ratio of extractant: substrate of 3:4, a pH value of 5.5, and a substrate concentration of 0.02 g/L. After five-successive cycles, the relative enzyme activity of the whole-cell catalysts was maintained above 50%. The flux of the membrane used for 10 h was restored to 75% when washed seven times with a 1% (v/v) aqueous HCl solution. Thus, the PVDF membrane reactor coupled with reaction and separation could be used in the industrial application of biocatalysis due to the increase of reaction efficiency and the decrease of product inhibition.