Wheat Straw Degradation by Trametes gibbosa: The Effect of Calcium Ions

Wheat straw is the major crop residue in Europe which makes it the most promising material for bioconversion. However, only 3% of annual production is used directly while the rest is considered as waste. A key step in processing of lignocellulosics is delignification by fungi and the presence of calcium can be of a great importance as it can modulate ligninolytic enzymes activities. Trametes gibbosa BEOFB 310 was used for solid-state fermentation of wheat straw in the presence of calcium in different concentrations. Samples were extracted after 19 days of fermentation and activities of Mn-oxidizing peroxidases and laccase were determined spectrophotometrically. Quantitative procedures were used to determine contents of hemicelluloses, cellulose, and lignin. Calcium induced activity of Mn-dependent peroxidase to a concentration of 5.0 mM (7185.2 ± 791.4 U L−1), which was threefold higher than in the control. Lignocellulose loss in wheat straw was stimulated by calcium addition and the maximum delignification was detected at concentration of 5.0 mM (52.9 ± 0.9%). Delignification was positively correlated to activity of Mn-dependent peroxidase. This study showed that wheat straw supplementation with calcium can significantly improve solid-state fermentation by increasing Trametes gibbosa Mn-dependent peroxidase activity and augmenting lignin degradation.