Sorghum straw for xylanase hyper-production by Thermomyces lanuginosus (D 2W 3) under solid-state fermentation

Abstract

This paper reports the production of very high levels of cellulase free xylanase and associated hemicellulases by an indigenous thermophilic isolate of Thermomyces lanuginosus (D 2W 3) using solid-state fermentation. Sorghum straw, an inexpensive and abundant source of carbon supported maximal xylanase activity (11,855 units/g dry substrate). Culturing T. lanuginosus D 2W 3 on sorghum straw and optimizing other culture conditions (media types, particle size of carbon source, inoculum level, inoculum age and additives), yielded increased levels of xylanase (39,726 units/g dry substrate). Further optimization of enzyme production was carried out using Box–Behnken design of experiments with three independent variables (inoculum level, glycerol and ammonium sulphate concentrations) which resulted in very high levels of xylanase, 48,000 ± 1774 units/g dry substrate, and 2.6 ± 0.2, 13.4 ± 0.56, 68 ± 1.7, 1.4 ± 0.08, 1.2 ± 0.05 (units/g dry substrate) of β-xylosidase, α-galactosidase, pectinase, β-mannosidase and α- l-arabinofuranosidase, respectively.