Microbial enzymes for hair removal: an integrated biotechnological approach for application in the leather tanning industry

ABSTRACT Microbial enzymes have been used for decades in a number of processes in the industrial, biomedical, environmental, and agro-food sectors. The dehairing phase of the leather tanning process is currently mediated by sulphur/sulphides chemicals, requiring expensive and complex procedures for water depollution and increasing safety risks for workers. This project is aimed at the development of a microbially-driven process for hair removal based on secreted enzymes. The first phase of the project consisted in the isolation of microorganisms naturally present on raw hides (cow skin) and displaying dehairing ability. A collection of 52 pure bacterial isolates was first screened for proteolytic activity (25 positive isolates) and then for their ability to grow on minimal media (10 positive isolates). The genome of these 10 isolates was sequenced and the supernatants containing secreted enzymes (and potential other metabolites) were tested for enzymatic activity and dehairing capacity at a laboratory scale. The secretome analysis reported the presence of more than 200 secreted proteins for each isolate and showed an increase in the release of hydrolytic enzymes during growth on minimal media. Further selection among the 10 isolates was based on proteomic analysis, pilot scale dehairing tests and yields after the downstream process The 4 isolates, selected on the base of the unhairing ability, secretome analysis and downstream yields, were subjected to further characterization to choose the most promising for the desired activity. Isolate 1Dm15, selected for the dehairing ability demonstrated at pilot scale, was grown in bioreactor and once the parameters were defined a scale-up of the process was performed. In conclusion, in this work we identified a Bacillus sp. strain able to grow on minimal media and secrete a pool of enzymes active in the dehairing of hides. This microbially driven process shows promising application in the industrial practice substituting the use of reducing agents.