Influence of yeast extract enrichment and Pycnoporus sanguineus inoculum on the dephenolisation of sugar-cane bagasse for production of second-generation ethanol

Pretreatment of sugar-cane bagasse (SCB) by laccases from Pycnoporus sanguineus under solid-state fermentation (SSF) can favour dephenolisation of the substrate prior to ethanol production. To define adequate conditions for this biological pretreatment, an experimental design and surface plot analysis were performed using as independent variables: yeast extract, fungal inoculum and substrate amounts after different incubation times. Laccase and cellulase activities and chemical characterisation of the substrate by C-13 CP/MAS (cross-polarization at magic angle spinning) NMR (nuclear magnetic resonance) were used as responses. After 60 days of SSF, yeast extract enrichment and low amounts of inoculum enhanced dephenolisation of SCB. Moreover, yeast extract reduced the quantity of crystalline cellulose without strongly promoting cellulases and polysaccharide degradation. High amounts of inoculum decreased laccase activities and substrate dephenolisation.