Gene cloning and characterization of an organic solvent-stimulated β-glucosidase and its application for the co-production of ethanol and succinic acid

Abstract

Enzymatic activity is a limiting factor for conducting the hydrolysis of lignocellulosic waste materials to generate renewable biofuels and biochemicals. A novel β-glucosidase (BGL) gene from Hypocrea sp. W63 was cloned and expressed in Pichia pastoris. The specific activity of the purified recombinant epB-BGL was 194.25 IU/mg using p-nitrophenyl-β-d-glucoside (pNPG) as a substrate. The optimum pH and temperature for epB-BGL were 5.0 and 70 °C, respectively. The activity of recombinant epB-BGL could be stimulated by 210% with the addition of 10% (v/v) ethanol. Furthermore, other organic solvents were also able to stimulate the activity of the enzyme at concentrations of 1% or 10% (v/v). Due to this distinctive performance, epB-BGL was used to release fermentable sugars from a sugarcane bagasse hydrolysate for ethanol and succinic acid co-production. In the experimental range, succinic acid was reached to 13.3 g/L with a higher yield of 0.91 g/g glucose and the ethanol was at a concentration of approximately 1.41 g/L, respectively. In addition, the by-product acetate, which could potentially be converted to other chemicals, was also produced at 9.745 g/L. This work demonstrates that recombinant epB-BGL can take advantage of incomplete hydrolysis to convert fermentable sugars, suggesting its potential application in lignocellulose bioconversion. Lignocellulose of sugarcane bagassese was hydrolysed to release fermentable sugars which with addition of epB-BGL for the co-production of ethanol and succinic acid.