Hyperexpression of xylanase from 2-deoxyglucose (2-DG) resistant mutant of Chaetomium thermophilum

Summary: xylanases have got central importance in the utilization of lignocellulosic material in industry. filamentous fungi have got tremendous importance for the production of xylanases. the expression of genes encoding the enzymes is regulated by different factors. the presence of readily metabolizable carbon sources like glucose,cellobiose,xylobiose,or xylose represses the synthesis of xylanase enzymes for the utilization of certain carbon sources such as xylan or cellulose and the process is known as catabolite repression. in filamentous ascomycetes,glucose repression is known to be mediated by cre1. in present study,mutagenesis was applied to a thermophilic fungus chaetomium thermophilum (atcc 28076) by treating spores with n-ethyl-n-nitrosourea (enu) and uv radiations. the mutagenized conidia were grown in liquid minimal medium having 2% xylose and 0.5% (w/v) 2-deoxyglucose (2-dg). colonies were selected with clear zones of dissolved xylan in toxic 2-dg presence as catabolite repressor on agar screening plates containing rose bengal. after mutation,36 mutants were selected and checked for xylanase activity. one mutant strain named as ctm/xyn-mbl gave 2.5 fold higher activity than the wild one in the presence of repressor glucose. the c. thermophilum strain with higher xylanase activity was successfully selected with 2-dg after random mutation with enu. this procedure for xylanase hyperexpression can be used for other fungal strains as well.