Alkaline hydrogen peroxide pretreatment of bamboo culm for improved enzymatic release of reducing sugars using recombinant cellulases

Abstract

Bamboo (Phyllostachys acuta) is considered one of the useful feedstocks of crop residues due to speedy growth, fastest propagation, and convenient harvesting. The influence of alkaline hydrogen peroxide (AHP) pretreatment of bamboo culm, its structural changes, and enzymatic hydrolysis were determined. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were used for the analysis of solid fraction after alkaline hydrogen peroxide treatment of bamboo culm. Recombinant enzymes were expressed in Pichia pastoris from newly identified Aspergillus niger BE-2. The obtained results revealed more hemicelluloses hydrolysis and improved cellulose accumulation in degraded part. The cellulose component was increased by 36.87%, hemicellulose decreased by 50.66%, and lignin by 37.94% in comparison with the chemical components in the raw material after AHP pretreatment. There is 111% increased yield reported for recombinant enzymes expressed in Pichia pastoris after 60 h of degradation as compared to untreated substrates biomass. A total of about 370 mg reducing sugars per gram dehydrated bamboo residues were obtained after AHP treatment. The results revealed that major structural changes take place in the physiology of the substrates after AHP treatment, including elimination of lignin and hemicellulose, and enhance the porous area for easy attack of recombinant cellulases. This investigation contributes in biomass conversion in a friendly environment to fulfil the energy requirement in the future challenges.