Enhanced conversion and extraction of ginsenoside Rg1 from Panax notoginseng using β-xylosidase mutants and an endoxylanase

Ginsenoside Rg1 is an important bioactive substance, which can be extracted from Panax notoginseng roots, and the conversion of its analogue notoginsenoside R1 will improve the yield of ginsenoside Rg1 in the extraction. Herein, the β-xylosidase xln-DT derived from Dictyoglomus thermophilum was engineered to convert notoginsenoside R1 to ginsenoside Rg1 effectively. Five mutants of the β-xylosidase were constructed semi-rationally, then their biochemical characteristics and corresponding structural features were investigated in detail. These mutants all exhibited higher catalytic efficiency toward pNPX compared with the wild-type, which were combined with an endoxylanase to extract ginsenoside Rg1 from P. notoginseng coupled with ultrasonic-assisted technology. After the optimization of enzymes and conditions, the extraction yield of ginsenoside Rg1 obtained by mutants S160N-R333Q and S160N-R333H under the conditions of pH 5.0 and 65 °C for 30 min reached 135.2 mg g−1. This fast process, without harmful reagents, represents a promising alternative for ginsenoside Rg1 production.