Effects of Copper, Manganese, and Glucose on the Induction of Ligninolytic Enzymes Produced by Pleurotus ostreatus during Fungal Pretreatment of Switchgrass

Abstract

Abstract. produces laccase and manganese peroxidase (MnP) to selectively degrade lignin and can be used as a biological pretreatment of lignocellulose biomass to enhance ethanol production. Exogenous copper and manganese have been reported to increase production of laccase and MnP, respectively. The effects of supplementing copper, manganese, or glucose to switchgrass inoculated with on ligninolytic enzyme activity were evaluated. Solutions of copper, manganese, glucose, or water were added with and without fungal inoculum at 75% moisture for 40 d at 28°C. Ligninolytic enzyme activities and biomass compositions were determined after the pretreatments. Simultaneous saccharification and fermentations (SSF) were conducted with the pretreated biomass. There were no significant differences between the supplement solutions on laccase activity, but MnP activities in copper-treated samples were significantly reduced. Fungal-pretreated samples had significantly less glucan, xylan, and lignin recoveries and significantly greater extractable sugars than non-inoculated controls. Ethanol yields during SSF corresponded with lignin degradation in the fungal-inoculated samples. Water-treated (control solution), fungal-inoculated samples showed the greatest lignin degradation and ethanol yields, while the copper-treated, fungal-inoculated samples had the lowest lignin degradation and ethanol yield. Manganese-treated and glucose-treated, fungal-inoculated samples had similar intermediate lignin contents and ethanol yields. Ethanol yield during SSF was significantly increased by fungal pretreatment compared to no pretreatment. Water alone was more effective than the copper, manganese, and glucose solutions added to the fungal pretreatments. Fungal pretreatment with provided significant lignin degradation to increase ethanol yield from switchgrass biomass. Keywords: Bioenergy, Biological pretreatment, Lignin.