Assessment of indigenous fungal biocatalysts towards valorization of delignified physico-chemically pretreated corn cobs and sugarcane bagasse

The conversion of plant-based lignocellulosic materials into alternative fuels entails various pretreatment strategies (chemical, physico-chemical or enzymatic) to boost the release of sugar constituents from biomass. This investigation reports the influence of different pretreatment techniques such as acid, alkali and steam treatment followed by enzymatic hydrolysis in single and (or) consolidated system, for releasing fermentable reducing sugars from sugarcane bagasse (SB) and corn cobs (CC) (major agricultural residues). Alkaline pretreatment facilitated maximal lignin removal, 83.2 and 69.4% from CC and SB, respectively, thereby expediting enzymatic hydrolysis by in-house xylanases produced from indigenously isolated Aspergillus tubingensis strains, AUMS60 (Xyn60) and AUMS64 (Xyn64A, B). The major operating conditions for enzymatic treatment of raw and pretreated residues were set at a substrate loading of 2% (w/v), an enzyme loading of 100-500 U g(-1) substrate and incubation at 40 degrees C, 140 rpm for 72 h. Treatment with Xyn60 and Xyn64A, B resulted in 81.4% (72 h) and 75.9% (24 h) saccharification of delignified SB and CC, respectively. Scanning electron micrographs and Fourier transform infrared spectra corroborated structural deformations induced by physico-chemical pretreatment processes, thereby validating the maximal enzymatic hydrolysis of delignified substrates. The analysis of enzyme hydrolysis products suggested higher saccharification of hemicellulosic fraction as compared with cellulose. The observations of the present study signify that the thermotolerant in-house enzymes show great potential in the saccharification of lignocelluloses within a short span of time and may open a new vista for biomass valorization in the bioenergy sector. (c) 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

Automated summary

This study investigates different pretreatment techniques for releasing fermentable reducing sugars from sugarcane bagasse and corn cobs. The alkaline pretreatment facilitated lignin removal and expedited enzymatic hydrolysis. Scanning electron micrographs and Fourier transform infrared spectra confirmed structural deformations induced by the pretreatment processes. The observations suggest that thermotolerant in-house enzymes show great potential in the saccharification of lignocelluloses within a short span of time.