RESUMO
Xylanases assume special importance in the paper and pulp industry as they replace toxic chemicals such as chlorine and chlorine dioxide for developing eco-friendly processes. This study evaluated xylanases produced by two fungi, the mesophilic fungus Trichoderma harzianum and a thermophilic fungus Chaetomium thermophilum. Among the polymeric substrates studied for xylanase production by both the fungi, birch wood xylan was found to be the best inducer of xylanases. Xylanases induction was subject to glucose repression. Partially purified xylanases preparation from T. harzianum and C. thermophilum exhibited optimal activities at pH 5 and 6 and at 60ºC and 70ºC, respectively. The apparent Km and Vmax values for the partially purified xylanase from T. harzianum using oat spelt xylan as a substrate were 4.8 mg mL-1 and 0.526 µmol min-1 mg-1, respectively. Whereas values of the partially purified xylanase from C. thermophilum were 2.96 mg mL-1 and 0.25 µmol min-1 mg-1, respectively. These findings in this study have great implications for the future applications of xylanases.