Valorization of tannery fleshing waste into nitrogen source for sustainable production of microbial enzymes

Fleshing waste, a major hazardous solid waste, can be sustainably managed through its conversion into value-added products, thereby mitigating its environmental footprint. In the present study, fleshing waste was enzymatically hydrolyzed using Bacillus subtilis MTCC 6537 protease and formulated into fleshings extract (FE) by spray drying process and its effectiveness as nitrogen source for various enzyme production was assessed. The spray drying process parameters were standardized by central composite rotatable design (CCRD), a tool of response surface methodology (RSM) and the optimized conditions yielded 96.70% of product recovery with 4.33% moisture content and 824.37 mg/g protein content. The results on chemical characterization of FE using FTIR and ¹H NMR are highly comparable with commercially available nitrogen sources. The potential of the FE as nitrogen source for production of microbial enzymes viz., protease (Bacillus subtilis), urease (Arthrobacter creatinolyticus) and lipase (Cryptococcus sp. and Aspergillus niger) was investigated. The resulting activities of 25.12 U/mL (protease), 17.93 U/mL (urease), 62.52 U/mL (Cryptococcus sp. lipase) and 25.19 U/mL (A. niger lipase) are highly comparable with that of the activities obtained with soyabean meal, meat extract, yeast extract and corn steep liquor as nitrogen sources. Thus, the preparation of nitrogen source from the tannery fleshing waste provides a sustainable solution for its disposal and a viable method for industrial production of enzymes at large scale.