Production of isoquercitrin from quercetin by biotransformation using Bascillus sp. CSQ10 isolated from Camellia sinensis cultivation soils

Abstract

Microorganisms are widely used to produce biologically active substances owing to their versatile ability to convert inexpensive compounds into physiologically active compounds. In this study, we isolated a microorganism capable of converting quercetin to isoquercitrin, a substance with various biological functions, from tea cultivation soils. A Bacillus strain was isolated and verified as Bacillus sp. CSQ 10 using 16sRNA gene analysis. When quercetin was fed as a substrate for Bacillus sp. CSQ10, isoquercitrin was produced through biotransformation. Furthermore, Bacillus sp. CSQ10 was able to biotransform isoquercitrin to quercetin-3-O-(6″-O-acetyl)-β-d-glucoside when the medium for biotransformation was replaced with yeast extract–peptone–dextrose (YPD) medium. Based on these findings, the biotransformation performance of Bacillus sp. CSQ10 was verified by optimizing the experimental conditions for the culture system at the laboratory scale in terms of temperature, cell density, biotransformation medium, and substrate concentration. The best biotransformation yields were achieved at 37 °C, 6.0 OD600, with YPD, and 181.0 mg/L of quercetin supply. Conclusively, 193.3 mg/L and 198.8 mg/L of isoquercitrin and quercetin-3-O-(6″-O-acetyl)-β-d-glucoside, respectively, were produced by Bacillus sp. CSQ 10 under these optimized experimental conditions.