Degradation of beech wood and wheat straw by Trametes gibbosa

Abstract

The aim of this study was to optimize cultivation conditions for Mn-oxidizing peroxidases and laccase production and selective degradation of beech wood and wheat straw lignin by Trametes gibbosa. To promote lignin degradation, the effect of different carbon and nitrogen sources, type of cultivation, enzyme dynamics and inducers were studied. Solid-state cultivation was optimal for lignin degradation. Wheat straw was the optimal carbon source for peroxidase activities stimulating the synthesis of numerous isoforms. The dynamics of enzymatic activities showed that 19-day-old fermentation is optimal and that activities were directly associated with enzyme production. Alteration of nitrogen sources and inducers was applied to increase the rate of lignin degradation and decrease cellulose degradation. The presence of nitrogen in the form of (NH4)2SO4 and concentration of 10 mM significantly increased the extent and selectivity of delignification of wheat straw compared with cellulose (44.1 vs. 36.1%). The most effective and selective wheat straw degradation (52.0% of lignin vs. 31.3% of cellulose) was achieved by enriching the optimum medium, as defined above, with 1.0 mM p-anisidine. The optimum conditions for wheat straw processing to achieve delignification and production of highly active ligninolytic enzymes by T. gibbosa were (NH4)2SO4/wheat bran medium supplemented with p-anisidine. This study indicated the significant potential of optimizing external factors as a promising tool for induction and selectivity in the degradation of lignocelluloses by T. gibbosa as a pretreatment for several biotechnological processes.