Regulatory mutations affecting the synthesis of cellulase in Bacillus pumilus

A wild strain of Bacillus pumilus was investigated for cellulase production, and putative mutants of this strain were screened for catabolite repression insensitivity after chemical mutagenesis using ethyl methanesulphonate (EMS) as a mutagenic agent. Out of four classes of mutants studied and classified according to their cellulase induction rate and level of cellulase production in the presence of high concentrations of glucose (2.6%w/v]), classes III and IV exhibited cellulase production up to 6.2 mg cellulase and 11.4 mg cellulase per gram of dry cell mass respectively. These mutants were referred to as catabolite repression-insensitive when compared to the wild strain which exhibited a total repression of cellulase synthesis under the same conditions. How EMS triggered the catabolite repression insensitivity in these mutants was not established. However this mutation brought out new strains of cellulase hyperproducers (mutants 6 and 11) in the presence of glucose when compared to other cellulase producers such as Aspergillus terreus, A. nidulans and Trichoderma reesei, which exhibited catabolite repression of cellulase synthesis. These mutants were selected as the most promising candidates for cellulase synthesis even at high glucose concentration.