Optimization of nutrient medium components for production of a client endo-β-1,4-xylanase from Aspergillus fumigatus var. niveus using a recombinant Aspergillus nidulans strain

Abstract

The goal of this study was to optimize a nutrient medium to maximize production of endo-β-1,4-xylanase (hereafter referred to as xylanase) using an Aspergillus nidulans modified by integration of an AFUMN-GH10 gene from Aspergillus fumigatus var. niveus. This modification resulted in high-yield secretion and accumulation of recombinant protein. Xylanases are an industrially relevant enzyme class used in food production and bioprocessing. High-titer production of xylanase was achieved by the cultivation of A. nidulans in the presence of maltose. A 2-level Plackett-Burman design was used to determine which medium components significantly affected xylanase production. NaNO3, maltose and KCl showed significant effects on xylanase production. These three medium components were further optimized using a 3-level Box-Behnken design, and their optimum levels were maltose, 120 g/L; NaNO3, 12 g/L and KCl, 2 g/L. A xylanase activity of 1,620 U/mL, (12,460 U/g of maltose) was observed when using the optimum medium, which was 280% greater than the maximum level obtained with the basic medium. Pyridoxine concentration in the optimum medium was reduced to limit growth and divert substrate toward enzyme production. Reducing pyridoxine from 1,000 μg/ml to 300 μg/ml increased xylanase activity to 1,790 U/ml. Optimized medium with reduced pyridoxine was then tested in a stirred tank bioreactor, which resulted in 112% more xylanase activity and 43% less dry cell weight compared with the medium containing 1,000 μg/ml of pirydoxine.