Studies on the application of ultrasound in leather enzymatic unhairingUltrasonics Sonochemistry

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Authors
Song Jian, Tao Wenyi, Chen Wuyong
Year
2010
DOI
10.1016/j.ultsonch.2009.10.003
Subject
Radiology Nuclear Medicine and imaging / Chemical Engineering (miscellaneous) / Acoustics and Ultrasonics

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Keywords:

Ultrasound

Enzymatic unhairing lean er u be e en as c unhairing capacities of enzymes. It is noted that amylase can interact with proteoglycans by attacking an im g has openin cess [ the slow diffusion of enzyme through skins.

According to Yates, approximately 70% of the total unhairing time was occupied by the enzymes reaching the follicle site which was the attacking region of the enzymatic unhairing [6]. Obviously, a considerable reduction in overall time would be achieved if the diffusion rate could be increased.

On the other hand, ultrasound is another clean technology which has potential use in leather industry. Sound waves with freIn fact, the medium was powder phase, not liquid phase, so the cavitation phenomenon was not produced [6]. In our research, the unhairing experiments were carried out in bath, and the cavitation therefore took effect.

On the other hand, whether ultrasound has any adverse effect on the physical properties of leather or not is a question. Moreover, the effect of ultrasound on the activities of enzymes must also be considered. In this study, the two questions were investigated [11,12].

During the enzymatic unhairing, the cementing substances known under the term ‘‘proteoglycans” or as ‘‘mucoids”, which * Corresponding author. Tel.: +86 510 83731996.

Ultrasonics Sonochemistry 17 (2010) 376–382

Contents lists availab o lsE-mail address: sj6807@163.com (S. Jian).Unfortunately, unhairing is a heavy pollution process. The convention lime–sulfide process produces a large amount of sulfide which is toxic and difficult to dispose [2]. Therefore, pressure is being placed on the industry to design and utilize cleaner technology. One such under consideration is enzymatic unhairing [3,4].

The main difficulty which hinders the utilization of enzymatic unhairing is to confine the proteolytic activity to the desired locations (including epidermis layer, hair follicles/hair and basement membrane) without damaging the collagen fiber structure which is the fundamental structure of leather [5]. The other problem is chemicals diffusing through the pores of skin matrix. Therefore, ultrasound can be applied in many unit operations in leather industry, such as soaking, liming, degreasing and fat liquoring [7–10].

However, less research about the combination of ultrasound and enzyme in unhairing has been reported. To the best of our knowledge, only Yates investigated the effect of ultrasound on enzymatic unhairing rate. According to Yates, ultrasound had little effect on enzymatic unhairing. But in Yates’ experiments, he prepared enzyme powder into a paste that was painted on the skins.Amylase

Protease

Diffusion 1. Introduction

It’s well known that unhairing is process in leather industry. Unhairin the removal of hair, and the other is brous structure for the following pro1350-4177/$ - see front matter  2009 Elsevier B.V. A doi:10.1016/j.ultsonch.2009.10.003saccharide side chains, thus having some unhairing capacity. Ultrasound can improve the unhairing capacity of amylase more effectively. Furthermore, amylase does no harm on the collagen fibrous structure and can be used safely without the need for a high degree of control. So it is possible to use amylase in enzymatic unhairing in combination with protease. In short, using ultrasound in amylase and protease unhairing is a promising clean technology.  2009 Elsevier B.V. All rights reserved. portant and necessary two main aims. One is g-up of the collagen fi1]. quency above the human audible range of 16 kHz are called ultrasound. When the ultrasound waves pass through a liquid medium, microbubbles can appear, grow, oscillate and collapse. This phenomenon is called cavitation. Cavitations produce remarkable mechanical and chemical effects such as agitation, emulsification and dispersion. Especially, ultrasound can enhance the rate ofAvailable online 9 October 2009 sound has little effect on enzyme activities, and also has little influence on the physical and mechanical properties of leather. Ultrasound can enhance the diffusion of enzyme through skins, thus improving theStudies on the application of ultrasound

Song Jian a,*, Tao Wenyi b, Chen Wuyong c a School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu 21403 b The Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan Univer cDepartment of Leather Engineering, Sichuan University, Chengdu, Sichuan 610065, PR a r t i c l e i n f o

Article history:

Received 23 July 2009

Received in revised form 10 September 2009

Accepted 2 October 2009 a b s t r a c t

Enzymatic unhairing is a c zation of enzymes in leath technology, ultrasound can effects of ultrasound on th the enzymatic unhairing w

Ultrasonics S journal homepage: www.ell rights reserved.leather enzymatic unhairing

R China , Wuxi, Jiangsu 214036, PR China a technology for leather industry. However, one problem hinders the utilinhairing is the slow diffusion of enzymes through skins. As another clean applied to accelerate the diffusion of enzymes through skins. In this work, zymatic unhairing were investigated. Effect of frequency of ultrasound on ompared, and 20 kHz was chosen in this work. Under our conditions, ultrale at ScienceDirect nochemistry evier .com/locate /u l tsonch

The salted pigskins were provided by Huajin Tannery Corpora(from Chendu Jiuzhou Ultrasonic Technology Co. Ltd., China). Two ultrasonic transducers (20 kHz and 40 kHz) were used and the ultrasound power density at both frequencies was adjusted to the same value 2.2 W/cm2. The probe-type transducer was immersed 5 cm under the surface of enzyme bath. 2.6. Effect of ultrasound on physical and mechanical properties of leather

Prepared pigskins placed in water were subjected to ultrasound irradiation (20 kHz), and were unhaired by lime–sulfide process, tanned, fatliquored, dried and buffed in the same process [18] (see Appendix II). Then the physical and mechanical properties of leather, including tensile strength, elongation at break and tearing load, were measured by standard methods [19] (the methods are similar to IUP8 and IUP6 which are the standard methods recommended by international union of leather chemists societies physical testing commission). Control tests without ultrasound were also done under the identical conditions, and compared with the tests with ultrasound irradiation. 2.7. Enzymatic unhairing