Improved yield of α-L-arabinofuranosidase by newly isolated Aspergillus niger ADH-11 and synergistic effect of crude enzyme on saccharification of maize stover

Abstract

Abstract Background In the view of depleting resources and ever-increasing price of crude oil, there is an urge for the development of alternative sources to solve the issue of fuel in the coming years. Lignocellulosic biomass is considered to be the most potential alternative resources for fossil fuel. Bioconversion of cellulosic and hemicellulosic components into fermentable sugars is the key step in producing fuel ethanol from lignocellulose. The enzymatic hydrolysis of lignocellulosic biomass needs a highly balanced composition of cellulases and hemicellulases. Commercial enzymes are usually poor in accessory hemicellulolytic enzymes like α-L-arabinofuranosidase. The addition of such accessory enzymes in combination with cellulase or hemicellulase plays a vital role in improving the total yield of fuel ethanol by enhancing the saccharification yield. Results The newly isolated fungal strain Aspergillus niger ADH-11 produced a maximum of 22.14 U/g of α-L-arabinofuranosidase under solid-state fermentation using wheat bran as the substrate and modified Mandels-Weber medium at 30°C after 180 h of incubation. The optimization of various fermentation parameters was performed by response surface methodology employing Plackett-Burman design followed by Box-Behnken design. The yield of α-L-arabinofuranosidase was enhanced by 2.34-fold after executing statistical optimization of various fermentative parameters. Crude α-L-arabinofuranosidase was found to be highly stable for 3 h at its optimum temperature (55°C) and pH (4.0). The assessment of the crude enzyme extract in saccharification of alkali-treated maize stover revealed that the supplementation of crude α-L-arabinofuranosidase to commercial cellulase and crude xylanase mixture increased the saccharification yield up to 730 mg/g of maize stover. Conclusions The newly isolated A. niger ADH-11 was found to be a potential producer of α-L-arabinofuranosidase. The crude enzyme was active at low pH and high temperature which makes it suitable for various industrial applications such as enzymatic saccharification of lignocellulosic biomass. The supplementation of α-L-arabinofuranosidase enzyme to commercial cellulases and hemicellulases improves the bioconversion of lignocellulosic biomass to a greater extent.