Modulation of hide protein resistance to enzymatic hydrolysis by calcium ions: rational design of enzyme-assisted unhairing for high-quality leather production
Abstract Enzymatic unhairing is an environmentally friendly and efficient method for leather processing. However, controlling protease hydrolysis remains challenging, leading to incomplete hair removal and potential grain damage. In modern leather manufacturing, the synergistic application of protea...
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| Language: | English |
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SpringerOpen
2025-08-01
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| Series: | Collagen and Leather |
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| Online Access: | https://doi.org/10.1186/s42825-025-00208-7 |
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| author | Hao Liu Xuyang Chen Juntao Kang Bi Shi Yunhang Zeng |
| author_facet | Hao Liu Xuyang Chen Juntao Kang Bi Shi Yunhang Zeng |
| author_sort | Hao Liu |
| collection | DOAJ |
| description | Abstract Enzymatic unhairing is an environmentally friendly and efficient method for leather processing. However, controlling protease hydrolysis remains challenging, leading to incomplete hair removal and potential grain damage. In modern leather manufacturing, the synergistic application of proteases, lime, and sulfide is increasingly employed to achieve satisfactory hair-saving unhairing performance. This study investigated the action mechanism of calcium ions in modulating the hydrolysis of hide proteins by proteases and proposed a balanced enzyme-assisted unhairing process. Enzymological and fluorescence spectroscopy analyses revealed that calcium ions could enhance the enzymatic resistance of hide proteins, including noncollagenous proteins and collagen, by binding to them. This enhancement in enzymatic resistance was more pronounced for globular proteins than for collagen fibers. In detail, following the addition of 20 g/L calcium ions, the hydrolytic activity of neutral and alkaline proteases decreased by 66.7% and 57.9% on bovine serum albumin, and by 40.7% and 48.1% on collagen fibers, respectively. Furthermore, the performance of the five unhairing processes was evaluated by varying the sequence of lime and protease application and type of protease used. Results indicated that while calcium ions exerted a protective effect on hide proteins and reduced damage to collagen fibers, they simultaneously hindered the removal of undesired noncollagenous proteins during unhairing. Consequently, the sequential application of lime followed by proteases resulted in the inadequate removal of interfibrillar substances, leading to unsatisfactory leather quality. Additionally, compared with an alkaline protease, a neutral protease was more easily inhibited under alkaline unhairing conditions, posed a lower risk of damage to the hide grain. Therefore, the neutral protease–lime–sodium sulfide unhairing process was chosen as the optimal strategy. This process involves the addition of neutral protease (50 U/g hide) for 60 min, followed by 1.0% lime for 90 min and 2.0% sodium sulfide for 90 min. These findings provide scientific insights for designing a controlled and efficient approach to enzyme-assisted unhairing processes. Graphical Abstract |
| format | Article |
| id | doaj-art-1d90b01c4e904c618cd6235cc3e7538a |
| institution | Kabale University |
| issn | 2097-1419 2731-6998 |
| language | English |
| publishDate | 2025-08-01 |
| publisher | SpringerOpen |
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| series | Collagen and Leather |
| spelling | doaj-art-1d90b01c4e904c618cd6235cc3e7538a2025-08-20T03:46:16ZengSpringerOpenCollagen and Leather2097-14192731-69982025-08-017111410.1186/s42825-025-00208-7Modulation of hide protein resistance to enzymatic hydrolysis by calcium ions: rational design of enzyme-assisted unhairing for high-quality leather productionHao Liu0Xuyang Chen1Juntao Kang2Bi Shi3Yunhang Zeng4Key Laboratory of Leather Chemistry and Engineering (Ministry of Education), National Engineering Laboratory for Clean Technology of Leather Manufacture, College of Biomass Science and Engineering, Sichuan UniversityKey Laboratory of Leather Chemistry and Engineering (Ministry of Education), National Engineering Laboratory for Clean Technology of Leather Manufacture, College of Biomass Science and Engineering, Sichuan UniversitySichuan Decision New Material Technology Co., Ltd.Key Laboratory of Leather Chemistry and Engineering (Ministry of Education), National Engineering Laboratory for Clean Technology of Leather Manufacture, College of Biomass Science and Engineering, Sichuan UniversityKey Laboratory of Leather Chemistry and Engineering (Ministry of Education), National Engineering Laboratory for Clean Technology of Leather Manufacture, College of Biomass Science and Engineering, Sichuan UniversityAbstract Enzymatic unhairing is an environmentally friendly and efficient method for leather processing. However, controlling protease hydrolysis remains challenging, leading to incomplete hair removal and potential grain damage. In modern leather manufacturing, the synergistic application of proteases, lime, and sulfide is increasingly employed to achieve satisfactory hair-saving unhairing performance. This study investigated the action mechanism of calcium ions in modulating the hydrolysis of hide proteins by proteases and proposed a balanced enzyme-assisted unhairing process. Enzymological and fluorescence spectroscopy analyses revealed that calcium ions could enhance the enzymatic resistance of hide proteins, including noncollagenous proteins and collagen, by binding to them. This enhancement in enzymatic resistance was more pronounced for globular proteins than for collagen fibers. In detail, following the addition of 20 g/L calcium ions, the hydrolytic activity of neutral and alkaline proteases decreased by 66.7% and 57.9% on bovine serum albumin, and by 40.7% and 48.1% on collagen fibers, respectively. Furthermore, the performance of the five unhairing processes was evaluated by varying the sequence of lime and protease application and type of protease used. Results indicated that while calcium ions exerted a protective effect on hide proteins and reduced damage to collagen fibers, they simultaneously hindered the removal of undesired noncollagenous proteins during unhairing. Consequently, the sequential application of lime followed by proteases resulted in the inadequate removal of interfibrillar substances, leading to unsatisfactory leather quality. Additionally, compared with an alkaline protease, a neutral protease was more easily inhibited under alkaline unhairing conditions, posed a lower risk of damage to the hide grain. Therefore, the neutral protease–lime–sodium sulfide unhairing process was chosen as the optimal strategy. This process involves the addition of neutral protease (50 U/g hide) for 60 min, followed by 1.0% lime for 90 min and 2.0% sodium sulfide for 90 min. These findings provide scientific insights for designing a controlled and efficient approach to enzyme-assisted unhairing processes. Graphical Abstracthttps://doi.org/10.1186/s42825-025-00208-7LeatherUnhairingProteaseCalcium ionsCollagenHide proteins |
| spellingShingle | Hao Liu Xuyang Chen Juntao Kang Bi Shi Yunhang Zeng Modulation of hide protein resistance to enzymatic hydrolysis by calcium ions: rational design of enzyme-assisted unhairing for high-quality leather production Collagen and Leather Leather Unhairing Protease Calcium ions Collagen Hide proteins |
| title | Modulation of hide protein resistance to enzymatic hydrolysis by calcium ions: rational design of enzyme-assisted unhairing for high-quality leather production |
| title_full | Modulation of hide protein resistance to enzymatic hydrolysis by calcium ions: rational design of enzyme-assisted unhairing for high-quality leather production |
| title_fullStr | Modulation of hide protein resistance to enzymatic hydrolysis by calcium ions: rational design of enzyme-assisted unhairing for high-quality leather production |
| title_full_unstemmed | Modulation of hide protein resistance to enzymatic hydrolysis by calcium ions: rational design of enzyme-assisted unhairing for high-quality leather production |
| title_short | Modulation of hide protein resistance to enzymatic hydrolysis by calcium ions: rational design of enzyme-assisted unhairing for high-quality leather production |
| title_sort | modulation of hide protein resistance to enzymatic hydrolysis by calcium ions rational design of enzyme assisted unhairing for high quality leather production |
| topic | Leather Unhairing Protease Calcium ions Collagen Hide proteins |
| url | https://doi.org/10.1186/s42825-025-00208-7 |
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