Screening white-rot fungi suitable for the biological pretreatment of wood biomass in methane fermentation

Abstract

The effectiveness of biological pretreatment by wood rot fungi for anaerobic methane fermentation from woody biomass was evaluated. Anaerobic fermentation was performed using co-culture of the cellulolytic acid- and hydrogen-producing anaerobic bacterium Clostridium thermocellum, and the methane-producing archaeon Methanothermobacter thermautotrophicus. For all of the fungi tested, four weeks of fungal pretreatment improved methane production from beech wood. Methane and hydrogen production varied among fungal treatments, and methane production was found to be dependent on the residual lignin content of the wood substrate. Among the fungi tested, the white rot fungus Phanerochaete sordida YK-624 showed the highest ligninolytic activity (33.2% of lignin removed) and methane production (5.9 mL/g pretreated beech wood). The fungus also improved methane production from cedar wood. Further, supplementation with 5% bran markedly increased methane production from beech and cedar wood substrates by 125% and 200%, respectively. The results suggested that methane production from fungal-pretreated wood was affected by the extent of delignification, and that optimizing the pretreatment conditions, such as the duration or the use of additives, is necessary for maximizing methane production.