Mutagenesis of Klebsiella edwardsii for mannanase synthesis

Abstract

The aim of the present study was to produce mutants from Klebsiella edwardsii capable of producing large quantity of mannanase. Mutants of K. edwardsii were generated by subjecting the cell culture to nitrous acid (0.1 M sodium nitrite in phosphate buffer). The mutants and the wild type were screened quantitatively for mannanase synthesis in basal medium containing Locust Bean Gum (LBG) as inducer. Twenty mutants were generated and screened for mannanase production in comparison with the wild type in submerged state fermentation. The isolated mutants were screened in comparison with wild type for the isolation of carbon catabolite activation mutants in the presence of 0.1, 0.5 and 1.0% (w/v) glucose as energy source. The entire mutant strains showed higher mannanase activities than the wild type, with the highest mannanase activity lied on mutant designated HN02. The supplementation of 0.1% (w/v) glucose in the fermentation media caused repression of mannanase synthesis in 60% of the mutants, while only 20% of the mutant exhibited higher mannanase activities when compared with wild type. The supplementation of 0.5 and 1.0% (w/v) glucose in the fermentation media enhanced mannanase production in 80% and 60% of the mutants respectively when compared with the wild type.