Improvement Of Cucurbitacin B Content In Cucumis Melo Pedicel Extracts By Biotransformation Using Recombinant Beta-Glucosidase

For the efficient biotransformation of cucurbitacin B 2-o-beta-d-glucoside (CuBg) to cucurbitacin B (CuB) in Cucumis melo pedicel extracts, the beta-glucosidase gene bglS-consisting of 1344 bp (447 amino acids) from Streptomyces sp. RW-2-was cloned and expressed in Escherichia coli BL21(DE3). The activity of recombinant beta-glucosidase with p-nitrophenyl-beta-d-glucoside (pNPG) as a substrate was 3.48 U/mL in a culture. Using the recombinant beta-glucosidase for the biotransformation of C. melo pedicel extracts, CuBg was converted into CuB with a conversion rate of 87.6% when the concentration of CuBg was 0.973 g/L in a reaction mixtures. The concentration of CuB in C. melo pedicel extracts was improved from 13.6 to 20.2 g/L after biotransformation. The present study provides high-efficiency technology for the production of CuB from its glycoside by biotransformation.