White-rot fungal pretreatment of wheat straw: Effect on enzymatic hydrolysis of carbohydrate polymers

Abstract

The aim of the study was the comparative analysis of degradation of wheat straw lignin by white-rot fungi and its implications on the efficiency of enzymatic hydrolysis of holocellulose. Peroxidases were found to be predominantly responsible for lignin degradation, even though high laccase activities were detected, especially in the initial stages of fungal culturing. The studied fungal species showed various ability to degrade lignin in wheat straw, which further affected the release of reducing sugars during enzymatic saccharification. The highest rate of lignin, hemicelluloses and cellulose degradation was noticed in the sample pretreated with Irpex lacteus. Among all the tested species, only Ganoderma resinaceum was found as a suitable lignin degrader, with 2-fold higher hydrolysis yield (51.1 ± 4.7%) than in the control. A key mechanism that enhances convertibility of carbohydrates is the selective lignin removal from biomass. Operating time, holocellulose loss and unpredictable fungal response to culturing conditions are the main challenges in fungal pretreatment of lignocellulosic feedstock.