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Traditionally, universally used pelt bating technologies rely on the application of trypsin, neutral and alkaline microbial proteases but suffer from complicated operation, limited bating efficiency and unsatisfactory leather performance. Therefore, devising a new pelt bating approach to achieve high bating efficiency and excellent leather performance has always been wished for by the leather industry. To pursue this goal, years of persistent research work enabled us to develop a novel approach for pelt bating by means of acidic proteases in pickling process. Initially, basic enzymatic characteristics and bating effectiveness of several typical acidic proteases in pelt pickling medium were investigated; then, the bating effectiveness through the quantitative characterization of protease activity of the optimal acidic protease was compared with that of the conventional bating enzyme. The results indicated that all of the selected acidic proteases had good salt-tolerance and exhibited optimum activity at pH 3.0–4.0. The novel pickling-bating method based on microbial origin acidic protease L80A led to an outstanding performance on pelt bating at the dosage of 150 U/mL of collagenolytic activity. The bating effectiveness of acidic protease L80A was comparable to and even better than that of trypsin BEM due to its moderate proteolytic ability. Moreover, the deep and even penetration of acidic protease in the pelt permitted it to produce soft, organoleptically stable and overall better quality crust leather than that of the conventional trypsin bating method. Additionally, pelt bating was performed along with the pickling process without extra inactivation and washing operation, making the bating operation more efficient, economical, and environment friendly. Results had made us to conclude that this cutting-edge acidic proteases based pickling-bating method could be the first step/ way forward to replace the decades-old traditional pelt bating technology.

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The degradation of elastin in skins during leather manufacturing can increase the yield area, softness and flatness of the leather, but, excessive degradation of elastin in leather processing induces looseness and increases veininess in the final leather product. However, the characterization of the degradation degree of elastin in skins and leathers was mostly studied through histological analysis qualitatively. There is an urgent need to develop a more efficient quantitative analytical strategy to evaluate the degradation of elastin in leather making processes. In this study, a simple and rapid HPLC method is developed for measuring elastin degradation in skins, leathers and leather processing liquors through determining the biological markers of elastin, namely desmosines. The separation of analytes was conducted on an C18 column (4.6 × 150 mm, 4.0 ?m) at 30 ?; the wavelength of diode array detector (DAD) was set at 275 nm; the mobile phases were composed of methanol and aqueous acetic acid (2.0 %, v/v). A gradient elution was carried out at a flow rate of 0.5 mL/min. It has been witnessed that Cr (III) has no effect on the retention time and peak area of desmosines, when the concentration of Cr (III) was in the range of 0 to 200 mg/L. In quantitative analysis, all of the calibration curves showed good linear regression (R2 ? 0.9990) within the tested ranges, and the recovery of desmosines was 100.9 % and 102.6 % for elastin hydrolysate and Cr-tanned elastin hydrolysate, respectively. The content of desmosines in elastin fiber, Cr-tanned elastin fiber and leather manufacturing liquors measured by established HPLC-DAD were comparable to the results obtained by amino acid analyzer. In the wet blue bating process, the quantitative analysis results are consistent with the histological staining results. The results demonstrate that the developed method is accurate and effective and can be readily utilized for the comprehensive process control of leather manufacturing.

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