Fungal Pretreatment of Corn Stover by Fomes sp. EUM1: Simultaneous Production of Readily Hydrolysable Biomass and Useful Biocatalysts

Abstract

In this work we studied two approaches for the revalorization of corn stover (CS): Feedstock for bioethanol generation and substrate for the production of biocatalysts. The practical application of two of these biocatalysts (laccases and cellulases) was also evaluated. The hydrolysis of CS was improved through a pretreatment with the thermotolerant fungus Fomes sp. EUM1; simultaneously, enzymatic extracts enriched with laccases or cellulases were obtained and applied for the pretreatment or hydrolysis of untreated CS. After 7 days, the fungal pretreatment promoted a significant increase in the release of reducing sugars (60%) and in the hydrolysis rate (50%). Lignin content decreased 61.2%, while holocellulose remained practically unchanged; a significant positive correlation (r = 0.948, p = 0.01) was found between laccase production and lignin degradation. Regarding biocatalysts application, the cellulases of Fomes sp. EUM1 showed catalytic properties similar to those of commercial enzymes; in addition, the pretreatment with laccases reduced 70% the processing-time (compared to the fungal treatment), and improved the release of reducing sugars and the hydrolysis rate by 26 and 29%, respectively. The pretreatment of CS with Fomes sp. EUM1 produces two valuable products: saccharificable biomass useful for bioethanol production and highly active enzymes applicable in bioconversion processes.