Heterologous expression of azoreductase-encoding gene azrS of Bacillus sp. MR-1/2 for enhanced azo dye decolorization an
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ORIGINAL PAPER
Heterologous expression of azoreductase‑encoding gene azrS of Bacillus sp. MR‑1/2 for enhanced azo dye decolorization and wastewater treatment Ali Abbas1 · Aqsa Mushtaq1 · Ayesha Iftikhar Cheema1 · Faisal Mahmood2 · Muhammad Asaf Khan1 · Tahir Naqqash3 · Mohsin Khurshid4 · Irfan Manzoor1 · Sher Muhammad1 · Muhammad Shahid1 Received: 8 April 2020 / Revised: 22 May 2020 / Accepted: 4 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In Pakistan, 55% of textile exports are contributed by textile-units of Faisalabad. The effluents of these textile units, being discharged without any treatment, contain the contamination of a huge amount of synthetic azo dyes. The objective of the current research was to evaluate the contribution of an azoreductase-encoding gene (azrS) from a pre-characterized azo dye decolorizing bacterial strain Bacillus sp. MR-1/2 in a high copy number host system (pUC19-T7-Top-T) of Escherichia coli strain DH5α followed by in-silico prediction of azoreductase enzyme (AzrS) function. The recombinant cells that contained azrS had a significantly higher rate of color removal in congo red and reactive black-5 dyes when compared to wild-type MR-1/2 and E. coli DH5α after 72 h of incubation. Moreover, we were able to show that the recombinant strain significantly reduced the values of all tested parameters (pH, EC, turbidity, TSS, and COD) in actual wastewater. In support of our results, it was also predicted through bioinformatics analysis that the deduced azoreductase protein of strain MR-1/2 is linked with the dye decolorization ability of the strain through NAD(P)H-ubiquinone: oxidoreductase activity. Furthermore, we also found that the deduced protein resembled closely related proteins of protein databank in many features, yet some unique features were predicted in the enzyme activity of strain MR-1/2. It was concluded that the recombinant strain could be examined in pilot-scale experiments for textile wastewater treatment. Keywords Azo dyes · Azoreductase · Decolorization · Gene expression · Transformation
Introduction
Communicated by Erko Stackebrandt. Ali Abbas and Aqsa Mushtaq contributed equally in this study. * Muhammad Shahid [email protected] 1
Department of Bioinformatics and Biotechnology, Government College University, Faisalabad 38000, Pakistan
2
Department of Environmental Sciences and Engineering, Government College University, Faisalabad 38000, Pakistan
3
Institute of Molecular Biology and Biotechnology, Bahauddin Zakariya University, Multan 60800, Pakistan
4
Department of Microbiology, Government College University, Faisalabad 38000, Pakistan
Water in urban areas is mainly polluted by the undeviating release of industrial effluents and sewage (Moglia et al. 2018). In Pakistan, textile industries produce a larger quantity of effluents carrying different types of salts, synthetic dyes, and metal ions which are terrifically dangerous for all living organisms and these effluents are being directly discharged into the env
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