Mutagenic treatment of aspergillus niger with hydroxylamine for improved cellulase synthesis from cellulosic wastes

Abstract

Cellulases present exciting possibilities for use in lignocellulosic bioconversion. Since microbial sources of cellulases appear to be the cheapest option, the search for strains of microorganisms with robust characteristics is open ended. Conidia of parental strains of Aspergillus niger isolated from soil were mutagenised with hydroxylamine. The selected mutant coded Aspergillus niger AH3, obtained after treatment with hydroxylamine was tested for the production of cellulase on carboxymethylcellulose, bagasse, corn cob and corn straw in shake flask incubated at 320C after ball milling the crystalline lignocelluloses to 250µ particle and the pH maintained at 4.8. Cellulase were evaluated and compared with Trichoderma reesei cellulase preparation (ECONASE CEP) as control. Maximum enzyme activity was at 96 and 120 hours for both mutant and wild strains fermenting amorphous and chrystalline cellulose respectively. Generally, enzyme expression in the lignocellulosics was in the order: bagasse > corn cob > corn straw. Maximal cellulase yield, 0.04888IU/ml/min., was obtained from bagasse fermented with the mutant than with wild, 0.04158, on same substrate thus translating to 18% increase in activity. The candidate mutant and sugarcane bagasse therefore holds great potential as chemical factory and raw material for commercial production of cellulases.