Integrated Physical and Proteomic Approaches Dissect the Effect of Leather Degradation by Bacteria

Landfills and incineration of leather wastes cause serious environmental pollution. In contrast, leather biodegradation by microbes is an environmentally friendly option for the disposal of leather. However, the microbial degradation mechanism is not fully understood. In this study, Bacillus licheniformis (Gram-positive bacterium) and Pseudomonas putida (Gram-negative bacterium) were isolated from leather artifacts. The effects of leather degradation by these two bacteria were systematically investigated. P. putida and B. licheniformis destroyed the morphology of the leather and caused obvious color aberration by darkening, greening, and bluing the leather. The tensile strength of sheep leather was significantly damaged by B. licheniformis. P. putida and B. licheniformis altered the elemental contents and disrupted the collagen structure of cow and sheep leathers to varying degrees. Proteomic profiling revealed a significant depletion of structural proteins in cow and sheep leather substrates mediated by B. licheniformis, including collagen alpha-1(II) chain, collagen type VI, and fibrillar collagen. In contrast, many proteases and peptidases of B. licheniformis were increased, such as acylaminoacyl peptidase, aminopeptidase, and carboxypeptidase, suggesting that these enzymes contribute to the degradation of leather proteins. These findings highlighted that B. licheniformis can effectively degrade leather by secreting proteases and peptidases. This study provided new insights into the conservation and biodegradation of leather, which will contribute to green development of the leather industry.