Chromium (VI) tolerance and bioaccumulation by Candida tropicalis isolated from textile wastewater
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(2020) 30:29
Sustainable Environment Research
RESEARCH
Open Access
Chromium (VI) tolerance and bioaccumulation by Candida tropicalis isolated from textile wastewater Sidra Ilyas1, Dilara A. Bukhari2 and Abdul Rehman1*
Abstract In the present study a yeast strain isolated from industrial wastewater, identified as Candida tropicalis, showed chromium (Cr) tolerance level up to 5 mM. Yeast grown in minimal salt medium containing Cr (VI) ions for 48 h and crude enzyme extracts were tested for chromate reductase activity. Optimum temperature and pH of chromate reductase were 30 °C and pH of 7. The enzyme activity was greatly enhanced in the presence of divalent metal cations. Total protein profile revealed some protein bands were present in hexavalent chromium [Cr (VI)] treated samples but were absent in non-treated samples, especially low molecular-weight protein bands in the mass range of < 25 kDa with greater intensity in Cr (VI) treated samples. Yeast cells were able to uptake Cr (VI) between 21 and 80 mg g− 1 within 2–12-d of time, indicating yeast strain promising potential for Cr (VI) removal from the wastewater. The present study results suggest that C. tropicalis is a suitable candidate for bioremediating chromium ions from the contaminated-environment. Keywords: Candida tropicalis, Cr (VI) resistance, Chromate reductase, Bioremediation
Introduction One of the most abundant elements on earth is chromium (Cr) existing in various oxidation states ranging from 0 to + 6 [1]. Cr is used in leather tanning, textile dyeing, chrome electroplating and finishing, metal processing industries, wood treatment, mining equipment, corrosion inhibition in power plants, manufacturing of refractory materials, and pigments. This extensive anthropogenic use has increased its concentration in environment higher than the recommended into the environment [2, 3]. The United State Environmental Protection Agency has declared it as a priority pollutant [4]. Cr poses several health threats to humans and has been reported to link to mutagenicity, genotoxicity, carcinogenicity, and allergenicity [5–7]. Generally, industrial effluents
contain multiple metals including chromium and chromium salts which have adverse effects on the microbial biota [8]. Chromium exists in several forms but trivalent Cr (III) and hexavalent Cr (VI) are the most stable forms [9]. Cr (VI) compounds are 100 times more toxic than Cr (III) due to having higher solubility, greater permeability through biological membrane systems and their successive interaction with intracellular macromolecules including nucleic acids and proteins [10, 11]. On the other hand, Cr (III) which is an essential trace element plays a significant role in glucose and fat metabolism by helping the smooth insulin functioning [12] in almost all types of living organisms. Cr (VI) inside the cells is partially reduced to highly unstable Cr (IV) and Cr(V) radicals that
* Correspondence: [email protected] 1 Department of Microbiology and Molecular Genetics, University of the Punjab, Lahore
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