Bacillus pumilus BpCRI 6, a promising candidate for cellulase production under conditions of catabolite repression

Abstract

Cellulose degrading organisms have been used for the conversion of cellulolytic materials into soluble sugars or solvents in several biotechnological and industrial applications. In this report, a mutant of Bacillus pumilus was obtained after chemical mutagenesis and screened for cellulase production. This mutant named BpCRI 6 was selected for its ability to produce cellulase under catabolite repression. Cellulase yield by BpCRI 6 was four times higher than that of the wild type under optimum growth conditions (pH 6.5, 25°C and Ca 2+ 1mM). In shaking flask cultures, production of cellulase by the wild type was completely repressed in the presence of 25 mM glucose, while BpCRI 6 strain still exhibited a residual cellulase production of 80 and 40% at 25 mM and 40 mM of glucose concentrations respectively. The mutant strain is stable and grows rapidly in liquid and solid media. Under conditions of catabolite repression (40 mM of glucose), the production of cellulase by this mutant is particularly significant when compared to Trichoderma reesei a well-known cellulase producer, which is under control of end-product inhibition. This is the first report of a successful catabolite repression insensitivity of cellulase production by a mutant of B. pumilus.

Lignocellulose biotechnology: issues of bioconversion and enzyme production

“…The first catabolite repressed Bacillus pumilus with cellulase yield four times higher than the wild type strain was created through mutagenesis (Kotchoni et al 2003).…”

Chemical Mutagenesis of Penicillium italicum for the Development of Catabolite Insensitive Mutants

“…This observation may also be applicable to mannanase production in mutants generated, because mannanase activity was reduced in some mutants in the presence of different sugar concentrations. Regulation of cellulase production had been well researched and documented (Moreno et al, 2001;Kotchoni et al, 2003); however, scanty information has been reported on regulation of mannanase production in microorganisms to date. The improvement in some of the mutants evaluated in media supplemented with mannose suggested that their regulatory genes might have lost their regulatory functions, thereby allowing the catabolite insensitive mutants to produce mannanase without inhibition by sugars.…”

Enzyme activity of a Phanerochaete chrysosporium cellobiohydrolase (CBHI.1) expressed as a heterologous protein from Escherichia coli

“…Lignocellulolytic microorganisms and their lignocellulolytic enzymes have many potential biotechnological applications ranging from the production of bio-fuel, chemicals, proteins, and to improving textiles, woodpulping and animal feeds for domesticated herbivores (Bhat and Bhat, 1997;Coughlan, 1985;Kotchoni et al, 2003;Ojumu et al, 2003). The white-rot, basidiomycete fungus, Phanerochaete chrysosporium, has attracted considerable research interest since it efficiently degrades all three components of lignocellulose (Baldrian, 2003;Tuomela et al, 2002;Yadav 2003).…”