Shahjahan Baig

Enhanced production of alkaline protease by a mutant of Bacillus licheniformis N-2 for dehairing

The purpose of the present investigations was to improve the yield of alkaline protease for leather dehairing by subjecting the indigenous proteolytic strain Bacillus licheniformis N-2 to various mutagenic treatments viz. UV irradiations, NTG (N-methyl-N-nitro-N-nitrosoguinidine) and MMS (methyl methane sulfonate). After screening on skim milk agar plates, a total of nine positive mutants were selected for shake flask experiments. Among these, the best proteolytic mutant designated as UV-9 showed 1.4 fold higher alkaline protease activity in preoptimized growth medium than the parent strain. The fermentation profile and kinetic parameters such u(h-1), Yp/s, Yp/x, Yx/s, qs, Qs, qp and Qp also indicated the superiority of the selected mutant UV-9 for alkaline protease production over the parent strain and rest of the mutants. The dehairing capability of mutant UV-9 alkaline protease was analyzed by soaking goat skin pieces for different time intervals (3-15 h) at 40 o C. A complete dehairing without degradation of collagen was achieved after 12 h, indicating its commercial exploitation in leather industry.

Impact of laccase enzyme inducers on solid waste compost maturity and stability

The influence of inducers of laccase produced by Pleurotus ostreatus-P1 on the physicochemical properties of solid waste compost was investigated. In order to examine the degree of humification and time period for maturity and stability of compost, three different treatments (T: laccase; T1: laccase+CuSO4; and T2: laccase+CuSO4+CaCl2) were inoculated on solid waste in the initial stage of the composting process. During the composting process, the carbon nitrogen ratio (C/N), nitrate (), ammonium nitrogen (), cation exchange capacity (CEC), humic acid (HA) and fulvic acid (FA) humification rate (HR), Humification Index (HI), and degree of polymerization (DP) were assessed for the evaluation of compost maturity and stability, and it was found that T2 treatment C/N, CEC, and HI was greater, 46.8%, 37.2%, and 38.46%, respectively, than T at the end of the maturation phase. Optimum degree of maturity was also appraised by the Germination Index, 98.25% was attained by T2, whereas 88.65% and 71.23% by T1 and T, respectively. Significant Pearson correlation was also found between compost characteristics such as C/N, CEC, HA, FA, DP, HI, and HR. In addition, also obstinate the mineralizations of nitrogen under laboratory incubation, using soil amended by 50 and 100 kg-N/ha and examined an increasing trend in nitrogen mineralization with the application rate. Moreover, it was concluded that the laccase inducers increase the disintegration and humification process during solid waste composting.