Hydrolytic enzymes production by Bacillus licheniformis growth on fermentation media formulated with sewage sludge

In this work, the production of hydrolytic enzymes by Bacillus licheniformis grown in media formulated with sewage sludge as the main carbon and nitrogen source with induction by keratins has been studied. The three main types of enzymes of industrial interest produced were proteases, lipases and cellulases. The addition of an inductor, keratin in our case, improves the production of these enzymes to reach a productivity of 16.89 mU/mL· day, 0.25 mU/mL·day, and 0.51 mU/mL·day for proteases, lipases and cellulases, respectively. The secretion of proteins and enzymes into the fermentation media was studied by electrophoretic and proteomic methods, which revealed the presence of proteases, lipases, and cellulases in the fermentation media, among other excreted proteins. Our results show that the growth of B. licheniformis in fermentation media formulated with sewage sludge as the main carbon and nitrogen sources, supplemented with keratin from feather meal as an inductor could be used for the industrial production of these enzymes, particularly of proteases.