Sustainable Denim Bleaching by a Novel Thermostable Bacterial Laccase
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Sustainable Denim Bleaching by a Novel Thermostable Bacterial Laccase Varsha Panwar 1 & Javed Nabibaksha Sheikh 2 & Tanmay Dutta 1 Received: 23 March 2020 / Accepted: 16 July 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Laccases have emerged as environment-friendly multifaceted biocatalysts for diverse biotechnological applications. Here, we isolated a high molecular weight (88 kDa) extremophilic laccase (LacT) from Brevibacillus agri, with the aim to exploit its extreme characters in denim bleaching. LacT has been characterized as a thermostable, acidophilic enzyme with high salt, organic solvent, and divalent metal tolerance properties. Denim bleaching efficiency of LacT was optimum at pH 4.0 and appeared to be surpassing over other reported laccases. LacT also exhibited remarkable efficacy in the decolorization of water-soluble health hazardous azo-dyes, and thus transpired to be a promising biobleaching and dye decolorizing agent. Keywords Bacterial laccase . Thermostable enzyme . Dye decolorization . Denim bleaching
Introduction Various industries like textiles, paper and pulp, electroplating, tanneries, and paint widely utilize more than 100,000 commercial dyes with an approximate annual production of 7 × 105– 1 × 106 tons [1–5]. Many of these dyes are carcinogenic [6, 7], intractable, and highly stable, and thus cannot be entirely eliminated from the effluents by conventional physicochemical methods. Nearly 15% of the used dyes are released into the environment as industrial discharge and subsequently pollute the aquatic environment, which in turn create significant havoc to the ecological balance [8]. In addition, denim bleaching in the textile industry requires sodium hypochlorite or potassium permanganate treatment, which not only releases hazardous chlorite but also the subsequent neutralization step produces enormous amounts of salts
* Tanmay Dutta [email protected]
1
Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
2
Department of Textile Technology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
Applied Biochemistry and Biotechnology
leading to disposal problem [9, 10]. To subside these issues, environment-friendly dyedegrading enzymes, especially laccase, have been introduced with increasing interest for the treatment of industrial effluents and denim bleaching in the textile industry. Laccases (benzenediol—oxygen oxidoreductase; EC 1.10.3.2) are primarily extracellular monomeric multi-copper oxidase enzymes, which catalyze the oxidation of a wide array of phenolic and nonphenolic compounds coupled to the four-electron reduction of molecular oxygen to water [11–14]. Laccase also can participate in catalyzing different types of reactions like ring cleavage of aromatic compounds, crosslinking of monomers, and degradation of polymers [15]. A small molecule mediator, e.g., 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), is required to act as an electron sh
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