Characteristics of Pleurotus sp. TD36 and its ability to reduce wood extractives in pretreatment for pulping

Lipophilic extractives of wood cause pitch deposition during pulp and paper production, leading to serious economic losses and environmental pollution. Natural seasoning of wood material before pulping can reduce wood extractives, but there is no control of the pulp yield and quality. Pretreatment of the wood chips with selected fungi is regarded as better controlled seasoning with effective removal of problematic extractives. Commercially available fungal preparations are effective mostly for softwood, but not quite suitable for Acacia mangium and hybrid hardwood—the main pulpwood of Vietnam. In this paper, a fungal isolate TD36 was identified as white-rot basidiomycete Pleurotus sp. TD36 based on the biological characteristics and phylogenetic analysis. Having high activity of ligninolytic enzymes, amylase and protease, Pleurotus sp. TD36 was able to degrade lignin-like compounds (guaiacol, Remazol Brilliant Blue), starch and casein. Degradation of wood extractives was evaluated by laccase and sterol esterase assays of the fungus in shake flask cultures and in pretreatment of Acacia wood chips. Favorable conditions for wood pretreatment were selected, including: inoculum size, 1% v/w; wood moisture, 60% v/w; temperature, 28–30 °C and 30 days. Under such conditions, Pleurotus sp. TD36 removed about 68 ± 2.75% of wood acetone extractives soluble in chloroform. Of that, about 73–89% of fatty acids and fatty alcohols, 76% of free sterols and 63% of sterol ester, were removed. Fungal pretreatment did not significantly affect the cellulose content of wood and Kraft pulp yield.