Preparation of γ-polyglutamic acid from enzymatic hydrolysate of poplar sawdust

Abstract

The treatment of forestry waste has always been an environmental problem. In this study, poplar sawdust was used to produce γ-polyglutamic acid (γ-PGA). Poplar sawdust was treated with acid and then hydrolyzed with cellulose. The enzymatic hydrolysate was used to produce γ-PGA. Through single factor and orthogonal experiments, the optimum enzymatic conditions were determined as follows: solid-liquid ratio 1:5, enzyme amount 22 FPU/g, pH 5.0 and 53 min. Under the enzymatic hydrolysate medium, the γ-PGA yield reached 30.87 ± 0.44 g/L, which was 5.11% higher than that in glucose medium (29.37 ± 0.43 g/L). In addition, the amount of glucose added to the medium was reduced, which realized the comprehensive utilization of various sugars in sawdust enzymatic hydrolysate. Although the fermentation time was prolonged by 4 h, this study provided a new and feasible method for the industrial utilization of forestry waste and the clean production of γ-PGA.