Wood Rot Fungi in the Advanced Biofuel Production

Abstract

The second-generation biofuel production process is focusing on the utilization of abundant lignocellulose. In this production, the pretreatment step is essential to degrade lignin and modify the chemical structure in raw lignocellulose. Subsequently, polysaccharide content in pre-treated lignocellulose is enzymatically hydrolyzed to monosaccharides in the saccharification step. Finally, these monosaccharides are utilized to produce biofuel in the ethanol fermentation step. White-rot fungi are efficient in 1) degradation of lignin; 2) enzymatic hydrolysis of polysaccharides; 3) ethanol fermentation of monosaccharides. Thus, it is possible to directly produce ethanol from various lignocellulosic substrates using white-rot fungi. The advanced biofuel production is targeting genetic/metabolic engineering to enhance the enzymatic activities of white-rot fungal enzymes that participate in all of pretreatment, saccharification and fermentation, finally resulting in higher efficient conversion from lignocellulose to ethanol. Recently, biofuel production is targeted in butanol fermentation. Among the biofuels, butanol is a high-value compound that is produced by the acetone-butanol-ethanol (ABE) fermentation process using the bacteria Clostridium. However, these bacteria without saccharification are unable to utilize lignocellulosic materials. To implement a reasonable butanol production, it is designed to use the co-culture of white-rot fungus and Clostridium to convert lignocelluloses economically into biofuels. In this co-culture, white-rot fungus plays a role in lignin degradation and saccharification, while Clostridium simultaneously ferments monosaccharides into butanol. To actualize second-generation biofuel production on a large industrial scale in near future, it is still in need of advancement on not only the efficient fermentation process but also suitable characteristics of lignocellulosic materials.