Optimization of β-1,4-Endoxylanase Production by an Aspergillus niger Strain Growing on Wheat Straw and Application in Xylooligosaccharides Production

Plant biomass constitutes the main source of renewable carbon on the planet. Its valorization has traditionally been focused on the use of cellulose, although hemicellulose is the second most abundant group of polysaccharides on Earth. The main enzymes involved in plant biomass degradation are glycosyl hydrolases, and filamentous fungi are good producers of these enzymes. In this study, a new strain of Aspergillus niger was used for hemicellulase production under solid-state fermentation using wheat straw as single-carbon source. Physicochemical parameters for the production of an endoxylanase were optimized by using a One-Factor-at-a-Time (OFAT) approach and response surface methodology (RSM). Maximum xylanase yield after RSM optimization was increased 3-fold, and 1.41- fold purification was achieved after ultrafiltration and ion-exchange chromatography, with about 6.2% yield. The highest activity of the purified xylanase was observed at 50 degrees C and pH 6. The enzyme displayed high thermal and pH stability, with more than 90% residual activity between pH 3.0-9.0 and between 30-40 degrees C, after 24 h of incubation, with half-lives of 30 min at 50 and 60 degrees C. The enzyme was mostly active against wheat arabinoxylan, and its kinetic parameters were analyzed (K-m = 26.06 mg center dot mL(-1) and V-max = 5.647 U center dot mg(-1)). Wheat straw xylan hydrolysis with the purified beta-1,4 endoxylanase showed that it was able to release xylooligosaccharides, making it suitable for different applications in food technology.

Automated summary

Plant biomass is a major source of renewable carbon, with hemicellulose being the second most abundant polysaccharide on Earth after cellulose. This study focused on the production of hemicellulases by a new strain of Aspergillus niger, resulting in significantly increased enzyme yield and high stability under various conditions, making it suitable for wheat straw xylan hydrolysis and applications in food technology.