Characterization of an extracellular β-glucosidase from Dekkera bruxellensis for resveratrol production

Hsiao-Ping Kuo ^a,1, Reuben Wang ^b,1, Chiao-Ying Huang ^a, Jinn-Tsyy Lai ^a, Yi-Chen Lo ^b,*, Shyue-Tsong Huang ^a,*

^a Bioresources Collection and Research Center, Food Industry Research and Development Institute, Number 331, Shih-Pin Road, Hsinchu 30062, Taiwan

^b Institute of Food Science and Technology, National Taiwan University, Number 1, Section 4 Roosevelt Road, Taipei 10617, Taiwan

Polygonum cuspidatum is a widely grown crop with a rich source of polydatin (also called piceid) for resveratrol production. Resveratrol is produced from piceid via enzymatic cleavage of the sugar moiety of piceid. In this study, Dekkera bruxellensis mutants were selected based on their high p-nitrophenyl-β-d-glucopyranoside and piceid conversion activities. The enzyme responsible for piceid conversion was a heterodimeric protein complex that was predominantly secreted to the extracellular medium and consisted of two subunits at an equal ratio with molecular masses of 30.5 kDa and 48.3 kDa. The two subunits were identified as SCW4p and glucan-β-glucosidase precursor in D. bruxellensis. Both proteins were individually expressed in Saccharomyces cerevisiae exg1Δ mutants, which lack extracellular β-glucosidase activity, to confirm each protein's enzymatic activities. Only the glucan-β-glucosidase precursor was shown to be a secretory protein with piceid deglycosylation activity. Our pilot experiments of piceid bioconversion demonstrate the possible industrial applications for this glucan-β-glucosidase precursor in the future.