Improvement of Cucurbitacin B Content in <i>Cucumis melo</i> Pedicel Extracts by Biotransformation Using Recombinant β-Glucosidase

Abstract

For the efficient biotransformation of cucurbitacin B 2-o-β-d-glucoside (CuBg) to cucurbitacin B (CuB) in Cucumis melo pedicel extracts, the β-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 β-glucosidase with p-nitrophenyl-β-d-glucoside (pNPG) as a substrate was 3.48 U/mL in a culture. Using the recombinant β-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.

Keywords

• cucurbitacin B
• o-β-d-glucoside%22%2C%22default_operator%22%3A%22AND%22%7D%7D%7D"> cucurbitacin B 2-<span style="font-variant: small-caps">o</span>-β-<span style="font-variant: small-caps">d</span>-glucoside
• <i>Cucumis melo</i> pedicel extracts
• biotransformation
• recombinant β-glucosidase