Design of efficient dispase one-bath strategy with low pollution and life cycle assessment for eco-sustainable leather processing

A reproducible dispase produced by Bacillus subtilis was employed in a one-bath strategy, to efficiently replace the conventional lime/alkali system that typically involves multiple pollution and cumbersome operations in the beamhouse. The components and contents of the dispase were identified and examined through ion mobility spectrometry (IMS). A comparative study was conducted to assess the effects of the one-bath strategy on dehairing and splitting collagen fibers, as well as its impact on the physical and thermal properties and aggregate structure of crust leather. The results indicated that dispase is a complex enzyme, primarily consisting of neutral metalloproteinase (A7UAM1 and A0A7U5AW19, 34.16 %), alpha-amylase (A7DWA9, H9BPX5, and O82953, 27.35 %), peptidase (A0A7U4I0I3 and A0A7U5AV24, 3.99 %), protease (M5AKX0, 2.32 %), 2’ 3’-cyclic nucleotide 2’-phosphodiesterase (A0A7U5CN75, 2.84 %), endoglucanase (H6WUK0, 0.78 %), and others (28.56 %). Compared to the conventional lime/alkali system, the efficiency of dehairing, splitting fibers, and bating for the alkali pre-expanded cattle hide using the one-bath strategy was enhanced by 42.3 %, simplifying the process significantly. The physical properties of crust leather were superior to those of the conventional strategy, while the pollution loads were considerably decreased and water consumption decreased by nearly 80 %. Most importantly, when employing NaOH pre-expanded cattle hide in the one-bath strategy, proteoglycans and elastin were rapidly hydrolyzed, with minimal hydrolysis of collagen. The dispersion of collagen fibrils, grain smoothness, fluffiness of collagen fibers, and physical properties of its crust leather are at their best. Furthermore, the hydrothermal shrinkage temperature was on par with that of the conventional strategy. According to the life cycle assessment (LCA) study, except for the environmental impacts of stratospheric ozone depletion, land use, and water consumption, the other impact categories from the newly developed one-bath strategy significantly outperformed the conventional strategy. This work and its results might provide bath methodological and theoretical contributions for simplifying the complex unit operations of conventional beamhouse, reducing environmental pollution, and developing high-quality eco-leather.