Lignocellulose bioconversion to ethanol by a fungal single-step consolidated method tested with waste substrates and co-culture experiments

Abstract

The Polyporales phlebioid white rot fungus Phlebia radiata is efficient in decomposing the wood main components, and in producing ethanol from lignocelluloses and waste materials. Based to these qualifications, the fungus was adopted for design of a consolidated bioprocess method to convert wood waste materials into ethanol without pretreatments. Higher ethanol yield was aimed by introducing collaborative fungal cultivations including isolates of Saccharomyces cerevisiae, other yeasts, and a brown rot fungus. Various waste lignocellulose materials such as wheat and barley straw, recycled wood-fiber based core board, recycled construction waste wood, spruce saw dust, and birch wood were applied to represent wood and non-wood waste lignocellulose of different origin, chemical content and structure. In solid-state single cultivations with the white rot fungus P. radiata, both core board and barley straw turned out as suitable substrates for the consolidated bioprocess. Up to 32.4 ± 4.5 g/L of ethanol accumulated in the solid-state core board cultivation in 30 days whereas with barley straw, 7.0 ± 0.01 g/L of ethanol was obtained. Similar concentrations of ethanol were produced in increased-volume and higher gravity bioreactor cultivations without chemical, physical or enzymatic pretreatment. In all, our consolidated method adopting a white rot fungus is a promising and economic alternative for second generation bioethanol production from waste and residual lignocelluloses.