Cellulase-free Xylanase: Production by Thermomyces lanuginosus TISTR3465 in solid state fermentation and efficiency on bioleaching

Abstract

The mixed substrate (12g) consisting of NaOH-treated corncob, wheat bran and rice husk at ratios between 5:5:2 to 4:6:2 were optimal ratios for xylanase production 250 ml Erlemeyer flask by Thermomyces lanuginosus TISTR3465 in static solid state cultivation at 70% initial moisture content at 50 ◦C. Addition of 0.12-0.75 g wood xylan to the substrates enhanced the enzyme production 1.30-1.58 folds. Addition of nitrogen sources to the mixed substrates did not increase the enzyme production indicating that wheat bran served as a sufficient nitrogen source. A temperature of 45-50 ◦C with 70% initial moisture content of the mixed substrates was the optimal conditions for the enzyme production by this strain. Aeration in a static tray solid-state culture was remarkably required for the enzyme production by this strain at higher thickness of substrate beds. Maximum xylanase activity, 1764 U/g dry solid, was obtained at a substrate thickness of 1 cm with an aeration rate of 0.24 l/g/h after cultivation for 5 days. The xylanase from T. lanuginosus TISTR3465 was found to be effective in release of reducing sugars from eucalyptus pulp. Treatment of pulp with -xylanase (220 U/g dry weight pulp) followed with 2% hydrogen peroxide significantly decreased in kappa number (5.7 U) and improved brightness up to 45.2%