White-Rot Fungi as Pretreatment Agents for Wood Destined for Biofuel Applications

Efficient and economical conversion of lignocellulosic biomass to biofuels is often hampered by the chemical recalcitrance of the material. Inexpensive and environmentally-friendly pretreatment processes are therefore desirable in order to lower the cost of biofuel production and minimize negative environmental impacts. To that end, we have explored the use of a naturally occurring white-rot fungus, Trametes versicolor, as a direct pretreatment agent for hardwood destined for biofuel applications. Specifically, we examined the pretreatment effects on the hardwood mixture after treatment with the wild-type strain of T. versicolor (52J) compared with those from a cellobiose dehydrogenase (CDH)-deficient strain (m4D) , to examine how a lack of CDH affects wood pretreatment. The effects of each strain of T. versicolor on the lignocellulose chemistry within the wood were examined after 12 weeks of incubation, as well as the physicochemical properties (pellet strength and energy content). At the laboratory scale, pretreatment with the mutant strain showed altered lignin structure and improved sugar yields, while the wild-type strain led to substantially increased pellet strength without impeding the overall energy content of the pellets. However, at the demonstration scale (150 L), the wild-type strain did not alter pellet strength, despite similar lignin extraction characteristics, glucose content, and energy content when compared to the laboratory scale. Therefore, further research will need to be conducted at the laboratory and demonstration scales to investigate how this fungus alters the structure of lignocellulose at the biochemical level (e.g., transcriptomic analysis), and how fungal pretreatment may affect other biofuel technologies, such as biomass gasification