A novel process for biodegradation and effective utilization of chrome shavings, a solid waste generated in tanneries, using chromium resistant Bacillus subtilis P13

Abstract

Present work deals with the development of an efficient and value-added process for the management of chrome shavings, a protein-rich, chromium-containing solid waste, produced in large quantities during the post-tanning operations in the leather industry, using Bacillus subtilis P13, a hot spring isolate. This bacterium was able to effectively degrade and grow using chrome shavings as the protein source and produce in the spent medium high levels of a keratinolytic serine protease that can be proficiently applied for the pre-tanning processing step of hide dehairing. The bacterium was moderately chromium resistant tolerating up to 35ppm and 350ppm of Cr(VI) and Cr(III) salts, respectively and showed bioaccumulation and bio-sorption of Cr(III) and Cr(VI). Growth profile and enzyme production were comparable in basal and production media containing chrome shavings. An efficient waste management process is described using solid substratum column reactor, leading to the liquefaction of the proteinaceous waste and the recovery of dehairing protease as concentrated product as well as Cr recovery for reuse in tanning. A continuous reactor scheme is proposed, where the biomass can be reused as the seed for chrome shaving hydrolysis for in-house waste management and by-product recovery in the tannery industry.