Lignocellulosic bioconversion by an optimized enzymatic cocktail from Irpex lacteus

Abstract

Lignocellulosic residues generated by the agro-forestry industry are low-cost renewable biomass, rich in cellulose, and can be valorized by converting it into second-generation bioethanol. This work aimed to convert the rice straw, pine, and eucalyptus sawdust into fermentable sugars by applying an enzymatic cocktail from Irpex lacteus LBM 034 optimized for enhancing cellulase levels. The most influential medium compounds in the production of the fungal cellulolytic enzymes were identified by a Plackett Burman design. The most significant compounds were xylan, carboxymethyl-cellulose, and peptone. The physical conditions for fungal incubation were optimized using response surface methodology, with 32 °C and pH 5.5 without agitation identified as the optimal conditions. Under these conditions, the level of endo-β-1,4-glucanases in the cocktail was 2.6 times higher than the original. The optimized fungal cocktail was then applied to hydrolyze the polysaccharides of NaOH-pre-treated rice straw, pine, and eucalyptus sawdust into fermentable sugars. The use of this enzymatic cocktail enabled efficient hydrolysis of rice straw, yielding in 27.19% and 38.18% of hemicellulose and cellulose conversion, respectively. This bioconversion of cellulose and hemicellulose of renewable biomass into fermentable sugars represents a cost-effective bioprocess for applications such as the production of lignocellulosic bioethanol.