Optimization and characterization of high-level thermostable xylanase produced from Aspergillus fumigatus PSF1 cultivated on wheat bran using response surface methodology

Although xylanase has versatile applications in the food, paper, and pharmaceutical industries, certain constraints prevail in industrial enzyme production under submerged fermentation, including the cost of production media and enzyme yield. The present study aimed to optimize essential media parameters (inoculum load, temperature, pH, carbon, and nitrogen) controlling xylanase activity using response surface methodology. After optimization, the xylanase was characterized to understand its properties under the best production conditions. In the current study, successful xylanase fermentation was achieved on day 6 under pre-optimized conditions, yielding a maximum xylanase activity of 445 IU mL−1. The physical parameters including inoculum load, temperature, pH, and nutritional sources like carbon and nitrogen in the present study, were subjected to optimization using response surface methodology, where the maximal xylanase activity was recorded when the inoculum load was 5 discs, pH 5.0, temperature 40 °C, beef extract 1 gL−1 as nitrogen source, and 4% wheat bran as carbon source for enhanced production of xylanase activity from 445 to 624 IU mL−1. The R² value of 0.98 indicated the effectiveness of the model, and the optimized conditions significantly increased xylanase yield. Using SDS-PAGE, the molecular weight of the xylanase was was determined to be 88 kDa,, and this was confirmed by a zymogram that revealed a distinct hydrolysis zone. Xylanase was highly stable at 50 °C, pH 6.0, and 0.8 M NaCl, and, when studying certain elements, it was found that manganese enhanced xylanase activity. The current study demonstrated the in-house culture of Aspergillus fumigatus PSF1 for enhanced xylanase activity, demonstrating its cost-effectiveness and suitability for various industrial applications.