Production of Thermostable Xylanase by Myceliophthora heterothallica in Solid-State Culture Using Agro-Industrial Residues

Xylanases are enzymes used in the conversion of lignocellulosic substances to fuels, digestion of animal feed, food and textile industries and as bleaching agents in paper production. The present study evaluated the production of a thermostable xylanase of the thermophilic fungus Myceliophthora heterothallica by solid-state fermentation of agro-industrial residues (sugarcane bagasse, sugarcane straw, wheat bran, and a mixture of the three substrates (1:1:1 w/w). Different cultivation parameters for the production of the enzyme were evaluated. The highest production of xylanase occurred in the mixture of the three substrates, after 4 days of cultivation. The activity of the enzyme was higher in the following conditions: water at pH 5.0 and incubation temperature of the fungus at 40 °C, with initial substrate moisture at 80%. The enzyme presented higher activity in the pH range between 5.0 and 6.5, with a peak at pH 5.0 and over 90% stability over a wide pH range (3.5 to 9.5). The optimum temperature was 65 °C and the enzyme showed 100% stability for 1 h, up to 60 °C. The results demonstrate that agro-industrial residues are efficient substrates for xylanase production, allowing the production of an enzyme with high stability under pH and temperature variations, a feature essential for its application in industrial processes.