Abstract
Conventional leather processing involving depilation of animal hide by lime and sulphide treatment generates considerable amounts of chemical waste causing severe environmental pollution. Enzymatic depilation is an environmentally friendly process and has been considered to be a viable alternative to the chemical depilation process. We isolated an extracellular protease from Pseudomonas aeruginosa strain MCM B-327 with high depilation activity using buffalo hide as a substrate. This 33 kDa protease generated a peptide mass fingerprint and de novo sequence that matched perfectly with LasB (elastase), of Pseudomonas aeruginosa. In support of this data a lasB mutant of MCM B-327 strain lacked depilatory activity and failed to produce LasB. LasB heterologously over-produced and purified from Escherichia coli also exhibited high depilating activity. Moreover, reintroduction of the lasB gene to the P. aeruginosa lasB mutant via a knock-in strategy also successfully restored depilation activity thus confirming the role of LasB as the depilating enzyme.
Highlights
Leather-making, is a by-product of the meat industry and reduces potential waste as well as contributing to economic growth [1]
We report the cloning of a candidate gene coding for the depilatory protease and present evidence using gene knock-out and knock-in strategies, showing that the depilatory activity is due to the product of the lasB gene
In P. aeruginosa MCM B-327, secretion of the depilating enzyme initiated only in early stationary phase and its accumulation in spent medium showed a steady increase till the culture reached the late stationary phase (72 h of incubation)
Summary
Leather-making, is a by-product of the meat industry and reduces potential waste as well as contributing to economic growth [1]. In the conventional pretanning process, depilation of animal hide is done by employing lime and sulphide. These two chemicals alone account for 70% of the total pollution in terms of biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS) and total suspended solids (TSS) [3]. The alkaline nature of tannery effluents and the high sulphide content pollute ground water sources and cause serious health problems to the tannery workers and people living in the vicinity of leather-processing industries [4], [5]. The proteases having high depilatory properties with mild or no collagenolytic activity are considered to be the best proteases for depilating animal hide [12], [13], [14], [15], [16]
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