ARTICLE IN PRESS JID: JTICE [m5G;May 15, 2017;9:6] Journal of the Taiwan Institute of Chemical Engineers 000 (2017) 1–9 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers journal homepage: www.elsevier.com/locate/jtice Enzyme mediated bacterial biotransformation and reduction in toxicity of 1:2 chromium complex AB193 and AB194 dyes Darshna K. Patel a , Devayani R. Tipre a , Shailesh R. Dave b,∗ a Department of Microbiology and Biotechnology, School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat, India b Department of Forensic Science, School of Sciences, Gujarat University, Ahmedabad 380009, Gujarat, India a r t i c l e i n f o Article history: Received 30 October 2016 Revised 6 February 2017 Accepted 27 February 2017 Available online xxx Keywords: Decolorization Toxicity Biodegradation Consortium Metal complex dyes a b s t r a c t A bacterial consortium was developed and applied for the treatment of 1:2 chromium complex azo dyes. Fed batch process was studied with optimized conditions for the decolorization of AB193 and AB194 up to 1100–1400 mg L −1 of cumulative dye concentration without further nutrient addition. Fed batch adapted consortium showed 39 and 42% enhanced decolorization for AB193 and AB194, respectively as compared to unadapted consortium. After bio-degradation of the dyes, chromium was not detected in the medium supernatant where as chromium was found sorbed on bacterial cell biomass. During the decol- orization process laccase, lignin peroxidase, tyrosinase, azoreductase and NADH-DCIP reductase enzymes were found to be induced. HPLC and FTIR analysis data confirmed the biodegradation of both the dyes. Biodegradation pathways were proposed on the basis of H 1 NMR and GC-HRMS analysis along with role of induced enzymatic system in the degradation process. 45–66% stimulation in growth was observed for Sorghum bicolor and Cicer aeriatinum when biodegradation products of both the dyes were used. Re- duction in toxicity on S. aureus and P. aeruginosa was recorded in the range of 58–100% and 43–100%, respectively. © 2017 Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers. 1. Introduction Important class of azo dyes which complex, cobalt, nickel and copper with azo ligands are referred as metal complex azo dyes (MCADs) [1,2]. Various industries utilizing MCADs include wool and nylon manufacturing units which generate colored effluents. As these dyes are metal complexes, various environmental dam- ages associated with such wastes are of more concern. Hence, requires efficient treatment prior to their disposal. High capital and operating costs of conventional treatment techniques along with incomplete removal of dye containing pollutant compounds produces further pollution problems [3,4]. Benefits of biological treatment techniques for dyes are well explained [5,6]. But, degra- dation of metal complex dyes is limitedly studied. Scanty reports are available explaining biodegradation of this group of dyes [7–9]. Hence, a biological treatment method is applied to treat 1:2 chromium (Cr) complex azo dyes. Various consortia have been already developed and screened against a range of MCADs are reported in earlier study [10]. On the basis of earlier results, focus was made on complete biodegradation study of two 1:2 ∗ Corresponding author. E-mail addresses: shaileshrdave@yahoo.co.in, srdave@gujaratuniversity.ac.in (S.R. Dave). chromium complex dyes viz. Acid blue 193 (AB193) and Acid black 194 (AB194) using already developed bacterial consortium. 2. Materials and methods 2.1. Dyes, media and chemicals AB193 and AB194 used in the study were generous gifts from Apex dyestuff Ltd., Vatva, Ahmedabad, Gujarat, India. Nutrient broth (NB) was purchased from Hi Media, India. Methyl red, ABTS (2,2-azinobis(3-ethylbenzothiazolin-6-sulphonic acid)), NADH (Nicotinamide adenine dinucleotide hydrogen), DCIP (Dichlorophe- nol indophenol) and other chemicals used in the study were pur- chased from Merck, India. 2.2. Consortium development, maintenance and preservation An indigenous bacterial consortium denoted as SDG was devel- oped for degradation of MCADs as mentioned elsewhere [10]. Con- sortium was prepared from MCAD contaminated soil sample col- lected from Vatva GIDC industrial estate. Sequential transfers were given for five times to enrich the bacterial populations degrading MCADs. From the enriched sample, bacterial cultures were isolated and identified by the standard procedures based on morphological, http://dx.doi.org/10.1016/j.jtice.2017.02.027 1876-1070/© 2017 Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers. Please cite this article as: D.K. Patel et al., Enzyme mediated bacterial biotransformation and reduction in toxicity of 1:2 chromium complex AB193 and AB194 dyes, Journal of the Taiwan Institute of Chemical Engineers (2017), http://dx.doi.org/10.1016/j.jtice.2017.02.027