A sustainable and cleaner speedy tanning system based on condensed tannins catalyzed by laccase

Condensed tannins, a sustainable and environmental-friendly vegetable tanning agent, is confined in the wide application of leather industry owing to its poor shrinkage temperature (Ts). In this work, the tanning effect of condensed tannins was enhanced by the green biocatalyst laccase. Meanwhile, the molecular weight and chemical structure of condensed tannins catalyzed by laccase were observed. Its polydispersity index (PDI) was decreased from 2.88 to 1.77 and the Mw from 6354 to 4041. The changes of relative molecular mass were confirmed by Gel permeation chromatography (GPC) analysis. The UV–visible spectroscopy (UV–vis) and X-ray photoelectron spectroscopy (XPS) spectra provided evidence for the catalyzing change from o-hydroxylation to o-quinones. From the aspects of the thermal stability, tensile strength, breaking elongation, tear strength, thickening percentage and morphological analysis, the leather tanned by catalyzed condensed tannins (BA) was proved to have more excellent physical properties contrast with that of the leather tanned by untreated BA. This indicates that the physical properties of leather tanned by BA were improved significantly, whilst the catalyzed sustainable agent can be independently used as a promising quick tanning agent of sheepskin light leather.