Biosynthesis of xylanolytic and xylan-debranching enzymes in Melanocarpus albomyces IIS 68

Melanocarpus albomyces IIS 68 synthesizes xylanase, beta-xylosidase and xylan debranching enzymes, namely, acetyl esterase, alpha-L-arabinofuranosidase and alpha-D-glucuronidase, when grown on various substrates. All five enzymes were found to be inducible. Wheat straw was found to be the best carbon source for production of extracellular xylanase (172 IU/ml) and the maximum number of xylanase isoenzymes. Out of the seven xylanase isoenzymes, xylanase Ic was found to be constitutive whereas the other six xylanases, namely, Ia, Ib, IIa, IIb, IIc and IId, exhibited more specific inducibility, the magnitude of which depended on the nature of the inducer. The best inducer for beta-xylosidase and acetyl esterase synthesis by washed mycelia was wheat straw whereas arabinose and birchwood xylan brought about the maximum induction of alpha-L-arabinofuranosidase and alpha-L-glucuronidase, respectively. In general, complex substrates were more effective inducers for xylanolytic enzymes than simple sugars.