Abstract

Chromium (Cr) (VI) has long been known as an environmental hazard that can be reduced from aqueous solutions through bioremediation by living cells. In this study, we investigated the efficiency of reduction and biosorption of Cr(VI) by chromate resistant bacteria isolated from tannery effluent. From 28 screened Cr(VI) resistant isolates, selected bacterial strain SH-1 was identified as Klebsiella sp. via 16S rRNA sequencing. In Luria–Bertani broth, the relative reduction level of Cr(VI) was 95%, but in tannery effluent, it was 63.08% after 72 h of incubation. The cell-free extract of SH-1 showed a 72.2% reduction of Cr(VI), which indicated a higher activity of Cr(VI) reducing enzyme than the control. Live and dead biomass of SH-1 adsorbed 51.25 mg and 29.03 mg Cr(VI) per gram of dry weight, respectively. Two adsorption isotherm models—Langmuir and Freundlich—were used for the illustration of Cr(VI) biosorption using SH-1 live biomass. Scanning electron microscopy (SEM) analysis showed an increased cell size of the treated biomass when compared to the controlled biomass, which supports the adsorption of reduced Cr on the biomass cell surface. Fourier-transform infrared analysis indicated that Cr(VI) had an effect on bacterial biomass, including quantitative and structural modifications. Moreover, the chickpea seed germination study showed beneficial environmental effects that suggest possible application of the isolate for the bioremediation of toxic Cr(VI).

Highlights

  • Wastewater from industrial applications contain potentially toxic metals and anonymous organics that cause alarming environmental pollution worldwide [1,2]

  • Chemicals and reagents used in this study were American Chemical Society (ACS) analytical grade unless stated otherwise

  • Geneversion sequence andIBM, blast analysis identified the bacterial as Klebsiella triplicates unless otherwise stated

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Summary

Introduction

Wastewater from industrial applications contain potentially toxic metals and anonymous organics that cause alarming environmental pollution worldwide [1,2]. Despite chromium (Cr) being a highly toxic metal, different tannery industries frequently use this metal [3]. Chromium discharge in wastewater contaminates water bodies, endangers aquatic lives, and poses a severe health hazard [4]. It is a public health concern that needs to be addressed by reducing toxicity or Cr load from industrial effluents [3]. There are about 250 leather tanning industries at Hazaribagh and Hemayetpur in Dhaka city, the capital of Bangladesh, which discharge liquid and solid wastes into canals and rivers, increasing. Res. Public Health 2020, 17, 6013; doi:10.3390/ijerph17176013 www.mdpi.com/journal/ijerph

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