Application of enzymes in leather processing: a comparison between chemical and coenzymatic processes

Ultrasound-assisted extraction of chromium from tanned leather shavings: A promising continuous flow technology for the treatment of solid waste

In this work, a continuous flow extraction system assisted by ultrasound (US) was developed for the extraction of Cr(III) from residual tanned leather shavings. US energy was delivered into the system by a tubular applicator (clamp-on tube US applicator). The effect of the US energy was investigated at 20 kHz of frequency and electrical input power of 75, 150, 300 and 600 W. Residence time and temperature profile were also evaluated. It was observed that the internal temperature profile was affected by the presence of US and inverted in comparison with the conditions without US. In this way, the temperature profile generated by the US was reproduced by using electrical resistances in order to compare the obtained results. The US intensity was measured using a hydrophone connected to a sound pressure meter. The use of the US did not alter the dynamic behavior of the system but increased the extraction efficiency when compared to the silent condition. US power above 75 W did not lead to increased extraction efficiency, when the residence time was 30 min. However, when 60 min of residence time were employed, the optimized US power was 150 W, resulting in an extraction efficiency of 71.7 ± 0.7 %, about 28 % higher when compared to the silent condition in the same temperature and other conditions. The US energy allowed a reduction in processing time and operational temperature when compared to the silent condition with the same temperature profile. The overall energy consumption with US was similar or lower than that observed without US, showing the feasibility of the proposed extraction system.

Microbial lipases and their industrial applications: a comprehensive review

Lipases are very versatile enzymes, and produced the attention of the several industrial processes. Lipase can be achieved from several sources, animal, vegetable, and microbiological. The uses of microbial lipase market is estimated to be USD 425.0 Million in 2018 and it is projected to reach USD 590.2 Million by 2023, growing at a CAGR of 6.8% from 2018. Microbial lipases (EC 3.1.1.3) catalyze the hydrolysis of long chain triglycerides. The microbial origins of lipase enzymes are logically dynamic and proficient also have an extensive range of industrial uses with the manufacturing of altered molecules. The unique lipase (triacylglycerol acyl hydrolase) enzymes catalyzed the hydrolysis, esterification and alcoholysis reactions. Immobilization has made the use of microbial lipases accomplish its best performance and hence suitable for several reactions and need to enhance aroma to the immobilization processes. Immobilized enzymes depend on the immobilization technique and the carrier type. The choice of the carrier concerns usually the biocompatibility, chemical and thermal stability, and insolubility under reaction conditions, capability of easy rejuvenation and reusability, as well as cost proficiency. Bacillus spp., Achromobacter spp., Alcaligenes spp., Arthrobacter spp., Pseudomonos spp., of bacteria and Penicillium spp., Fusarium spp., Aspergillus spp., of fungi are screened large scale for lipase production. Lipases as multipurpose biological catalyst has given a favorable vision in meeting the needs for several industries such as biodiesel, foods and drinks, leather, textile, detergents, pharmaceuticals and medicals. This review represents a discussion on microbial sources of lipases, immobilization methods increased productivity at market profitability and reduce logistical liability on the environment and user.

Progress and mechanism of breaking glycoconjugates by glycosidases in skin for promoting unhairing and fiber opening-up in leather manufacture. A review

Abstract

The glycoconjugates, herein glyco-proteins, existing in animal skins are closely related to the effectiveness of unhairing and fiber opening-up. Glycosidases have been used in leather making processes to reduce pollutants and improve leather quality. But the selection of glycosidases is still blind because the related mechanisms are not well understood yet. Hence, the animal skin structures and glycoconjugates components, the advances in the methods and mechanisms of removing glycoconjugates related to unhairing and fiber opening-up in leather manufacture, the kinds, compositions, structures and functions of typical glycoconjugates in skin are summarized. Then the approaches to destroy them, possible glycosidases suitable for leather making and their acting sites are analyzed based on the recognition of glycoconjugates in skin and the specificities of glycosidases toward substrates. It is expected to provide useful information for the optimization of glycosidases and the development of new enzymes and the cleaner technologies of unhairing and opening up fiber bundles assisted by glycosidases.

Graphical abstract

Improving characteristics of biochar produced from collagen-containing solid wastes based on protease application in leather production

Preparation of biochar from industrial solid wastes is receiving increasing attention in recent years. In this paper, alkaline protease, neutral protease and collagenolytic protease are used in preliminary steps of leather production, which are expected to replace the traditional chemical agents while preserving quality of the finished leather. The protease application has remarkable positive influence towards characteristics of biochar prepared by collagen-containing solid wastes produced in preliminary steps. The enzymatic action time should be more than 3 h for complete permeation and catalysis, and the diameters of treated collagen fibers were in the range of 10 to 20 nm. The micro-cracks occurring on collagen fibers would have an obviously impact on the formation of biochar. The application of proteases reduce the pollution of traditional production through replacing traditional polluted chemicals, and the characteristics of biochars are obviously improved with good surface area and high carbon content approximately 70%. Its surface area can reach 967 m²/g. These biochars contain oxygen-containing functional groups, and the oxygen content of biochars are all over 20%. The enzyme application in leather production are effective to the properties of biochars prepared by collagen-containing solid wastes. This research can serve as a basis for the preparation of biochar derived from of natural bio-wastes thereby promoting the development of biomaterials.

Alkaline protease for an efficacious rehydration of skin matrix by a novel Bacillus crolab MTCC 5468 in sustainable leather production: a green approach

OBJECTIVES

The utilization of biotechnology in leather sector has more extensive in modern years; more particular to proteolytic enzymes and employed in several steps of the leather making such as soaking, dehairing, bating, solid waste management etc. The current study evaluates the performance of alkaline protease from Bacillus crolab MTCC 5468 in single soaking of goat skins matrix by comparing with the conventional multiple soaking processes.

RESULTS

According to the obtained results, the optimum concentration for maximum rehydration of goat skins was accomplished at 1.0% (v/w) of alkaline protease at duration of 3 h over traditional rehydration method (4-6 h). The moisture level, total protein, chloride content and total organic carbon of enzymatic rehydration was superior to that of conventional rehydration and it was also used to measure the effectiveness of rehydration process. Scanning electron microscopic images of enzymatically processed leather exhibits enhanced opening of fiber bundles and smooth grain surface than conventional method. Furthermore, the alkaline protease treated leather exhibited improved moisture uptake, removal of chlorides and suppleness because of hydrolysis of non-collagenous proteins as indicated by well opened up fiber bundles in histological analysis.

CONCLUSIONS

The application of alkaline protease in rehydration operation of leather production confirmed scope for diminishing water quantity around 66.6%, soaking duration at 50%, minimizing use of harmful dehairing chemicals at 50-60%, thereby, eliminating the bating operation during pre-tanning. These outcomes suggest that alkaline protease have potential application in rehydration of skins for immense environmental concerns of leather tanning sectors.

Alkaliphilic Enzymes and Their Application in Novel Leather Processing Technology for Next-Generation Tanneries

Leather manufacturing involves conversion of raw skin and hides into leather (stable material) through series of mechanical and chemical operations. The leather industry has attracted public outcry due to severe environmental degradation, pollution and health and safety risks. Currently the industry faces serious sustainability challenge due to extensive use of toxic chemicals and generation of hazardous waste. This chapter describes the polluting chemicals consumed in different stages of conventional leather processing and the nature of waste generated. In order to overcome the hazards caused by toxic chemicals in tanneries and protect the environment, enzymes have been identified as a realistic alternate for chemicals used in beam house operation and waste management. Alkaline active proteases of alkaliphiles offer advantages over the use of conventional chemical catalysts for numerous reasons, for example, they exhibit high catalytic activity and high degree of substrate specificity, can be produced in large amounts and are economically viable. This is because the enzymes of these alkaliphiles are capable of catalysing reactions at the extremes of pH, temperature and salinity of leather-manufacturing processes.The chapter describes how alkaliphilic enzyme can effectively be used in soaking, dehairing, bating and degreasing operations to prevent waste generation, help in recovery of valuable by-products, reduce cost and increase leather quality. It is worth noting that protease has the capability to replace sodium sulphide in the dehairing process. In addition, alkaline proteases have shown remarkable ability in bioremediation of waste generated during the industrial processes. Intensive efforts are being directed towards chemical-based industries to use viable clean technology in their operation to reduce their negative impact on the environment. Similarly, leather industry should adopt the use of eco-friendly reagents such as enzymes to achieve long-term sustainability and clean environment and avert health hazards. Application of enzyme technology in clean leather processing strongly depends on legislation, political will and allocation of financial resources in research, development and implementation of this potentially powerful technology. Graphical Abstract.

Ionic liquids: new age materials for eco-friendly leather processing

The manufacture of leather is a challenging and complicated process, which converts natural biomaterial to various high end applications.