Improvement of lignocellulosic biomass conversion by optimization of fungal ligninolytic enzyme activity and molasses stillage supplementation

Abstract

Fungal treatment of lignocellulose is an ecologically and economically acceptable method. However, it needs improvement to increase the hydrolysis rate. A novel combination of multiple response optimization of ligninolytic activity of Trametes hirsuta F13 and supplementation of the lignocellulosic substrate (beechwood sawdust) with sugar beet molasses stillage was employed to improve and manage the desired type of fungal ligninolytic activity leading to a significant enhancement of biomass saccharification. Obtained optimal cultivation conditions (molasses stillage concentration, 13%; substrate moisture, 63%; and temperature, 25 °C) provided the desired combination of laccase and manganese-dependent peroxidase activity, and maintained the activities longer and at higher values (51.5 ± 3.5 U/L and 91 ± 4.24 U/L, respectively) than the conditions without molasses stillage (21.5 ± 2.12 U/L and 31.5 ± 4.9 U/L, respectively). Enzyme hydrolysis of the substrate treated for 7 days in the presence of molasses stillage released 20.54 ± 0.80 mg/mL fermentable sugars, and 63.58 ± 1.47 mg/mL from 18-days treated substrate, while sugar concentrations released from the substrates pretreated without the supplementation were 16.84 ± 0.30 mg/mL and 53.63 ± 2.16 mg/mL, respectively. The proposed new approach of the lignocellulose supplementation with sugar beet molasses stillage and manipulation and improvement of fungal ligninolytic activity proved to be a promising solution for the enhancement of lignocellulose bioconversion.