Hexavalent chromium reduction potential of Cellulosimicrobium sp. isolated from common effluent treatment plant of tannery industries

https://doi.org/10.1016/j.ecoenv.2017.08.040Get rights and content

Highlights

  • Characterization of Cr(VI) reducing bacterium from tannery wastewater.

  • 16S rRNA gene sequence analysis identified bacterium as Cellulosimicrobium sp.

  • SEM, EDX & FTIR analysis.

  • MIC values ranging from 250 to 800 mg/L for different heavy metals.

Abstract

Present study deals with the isolation and characterization of a bacterium capable for the effective reduction of Cr(VI) from tannery wastewater. Based on the 16S rRNA gene sequence analysis, this bacterium was identified as Cellulosimicrobium sp. (KX710177). During the Cr(VI) reduction experiment performed at 50, 100, 200,and 300 mg/L of Cr(VI) concentrations, the bacterium showed 99.33% and 96.98% reduction at 50 and 100 mg/L at 24 and 96 h, respectively. However, at 200 and 300 mg/L concentration of Cr(VI), only 84.62% and 62.28% reduction was achieved after 96 h, respectively. The SEM analysis revealed that bacterial cells exposed to Cr(VI) showed increased cell size in comparison to unexposed cells, which might be due to either the precipitation or adsorption of reduced Cr(III) on bacterial cells. Further, the Energy Dispersive X-ray (EDX) analysis showed some chromium peaks for cells exposed to Cr(VI), which might be either due to the presence of precipitated reduced Cr(III) on cells or complexation of Cr(III) with cell surface molecules. The bacterium also showed resistance and sensitivity against the tested antibiotics with a wide range of MIC values ranging from 250 to 800 mg/L for different heavy metals. Thus, this multi-drug and multi-metal resistant bacterium can be used as a potential agent for the effective bioremediation of metal contaminated sites.

Introduction

The contamination of environments (soil and water) with various toxic metals is a serious threat for ecosystem and human health, and requires the implementation of appropriate remedial measures. Heavy metals, such as chromium, cadmium, mercury, arsenic, lead etc. are considered as major environmental pollutants due to their toxic effects on environment as well as on human health (Ray and Ray, 2009). In developing countries, different types of industrial wastes (solid and liquid) containing a number of toxic metals in high concentration are directly or indirectly discharged into the environment without adequate treatment (Dixit et al., 2015, Chandra et al., 2009). Industries such as metallurgical, chemical, refractory brick, leather, wood preservation, pigments and dyes are the major sources of toxic metals contamination in environment (USEPA, 1998, Ryan et al., 2002).

However, tannery industries are the major source of chromium contamination into the environment. Tannery industries consume a huge volume of water in tanning of hides and skin, as it is wholly a wet process and generate ~ 30–35 L of wastewater per kg skin/hides processed (Nandy et al., 1999). There are ~ 3000 tanneries in India, mainly located in the states of Tamil Nadu, West Bengal, Uttar Pradesh, Andhra Pradesh, Bihar, Gujarat, and Maharashtra, generating total ~ 1,75,000 m3 wastewater per day (Kaul et al., 2005). In Uttar Pradesh, ~ 444 tanneries are in operation mainly in Kanpur and Unnao region generating 22.1 MLD of wastewater per day (CPCB, 2013) and this wastewater is reported to contain 0.01–4.24 mg/L of Cr(VI) (MOWR, 2013). However, most of the tanneries (nearly 80%) are engaged in chrome tanning process that releases ~ 2000–3200 t of Cr into the environment annually (Belay, 2010). The Cr concentration in tannery wastewater ranges between 2000 and 5000 mg/L, which is much higher than the permissible limit of 2 mg/L for wastewater discharge (Belay, 2010).

Like organic pollutants, metals are not degraded and tend to accumulate into the environment, may enter the food chain and cause toxic, genotoxic, mutagenic and carcinogenic effects (Chandra et al., 2011). Chromium compounds are well known to have toxic, genotoxic, mutagenic, and carcinogenic effects on humans, animals, plants, and as well as in microbes (Cheung and Gu, 2007, Mishra and Bharagava, 2016). In nature, chromium exists in several oxidation states ranging from − 2 to + 6, but only trivalent (III) and hexavalent (VI) forms of chromium is most prevalent and stable. Out of these two forms, hexavalent chromium [Cr(VI)] is highly toxic, mutagenic, teratogenic, carcinogenic to human and animals and has been designated as priority pollutant by US Environmental Protection Agency (USEPA) (1998). If Cr(VI) concentration into the environment exceeds > 0.05 mg/L, then it may affect the human physiology and if enter the food chain, it may cause severe health hazards such as skin irritation, nasal irritation, ulceration, eardrum perforation, and lung carcinoma etc. (WHO, 2011, Srinath et al., 2002).

Cr(VI) also acts as a strong oxidizing agent and exists only in oxygenated forms as hydro-chromate (HCrO4-), chromate (CrO4-) and dichromate (Cr2O7−2) ionic species in aqueous systems. Cr(VI) compounds are comparatively more toxic than Cr(III) compounds due to their higher solubility in water, rapid permeability through biological membranes and subsequent interaction with intracellular proteins and nucleic acids (Thacker et al., 2006; Cheung and Gu, 2007). Although a number of conventional/traditional methods are reported either for removal or detoxification of Cr(VI) from industrial wastes such as chemical precipitation, reverse osmosis, ion-exchange, filtration, membrane technologies, evaporation recovery, absorption on coal, activated carbon, alum, kaolinite, and fly ash etc. (Saxena et al., 2016, Ahluwalia and Goyal, 2007). These methods are very costly, less effective and also generate a metal rich sludge as secondary pollutants. Therefore, it becomes very essential to develop an eco-friendly, cost-competitive and effective method for removal/detoxification of Cr(VI) for the safety of environment and human health protection.

However, microbial reduction of toxic Cr(VI) to non-toxic Cr(III) by chromium resistant bacteria (CRB) is the most pragmatic approach that offers an economical as well as eco-friendly option for chromate detoxification and bioremediation. Microbes have diverse resistance mechanisms to cope with chromate toxicity that enable them to survive in such harsh environmental conditions (Cervantes and Campos-Gracia, 2007). These detoxification strategies include biosorption, bioaccumulation and biotransformation by enzymatic reduction, diminished intracellular accumulation through either direct obstruction of ion uptake system or active chromate efflux, precipitation, and reduction of Cr(VI) to less toxic and less mobile Cr(III) (Cheung and Gu, 2003, Ramirez-Diaz et al., 2008). Hence, the objectives of this study were to isolate and characterize chromium resistant bacteria, which should be capable to reduce/detoxify the toxic Cr(VI) into less toxic and less mobile Cr(III) for environmental cleanup and human health safety.

Section snippets

Collection of tannery wastewater

The tannery wastewater was collected from Common Effluent Treatment Plant (CETP) of Jajmau Unit, Kanpur (26°26'59.7228"N and 80°19'54.7335"E), Uttar Pradesh, India in a pre-sterilized conical flask (Cap. 2 L), brought to laboratory, maintained at 4 °C and used in analysis of physico-chemical parameters as well as for the isolation of bacterial strains capable for the reduction of hexavalent chromium.

Physico-chemical analysis of tannery wastewater

The physico-chemical analysis of tannery wastewater was made in triplicate as per the standard

Physico-chemical characteristics of tannery wastewater

Thephysico-chemical analysis of tannery wastewater reveals that it was alkaline in nature (pH 8.49 ± 0.2), light yellowish in color and deficient in dissolved oxygen. In addition, the BOD, COD, total solids, TDS, TSS, phenol, sulphate, and total chromium content was 160 ± 15.8, 322 ± 28.6, 11,028 ± 805.2, 3491.3 ± 239.4, 194 ± 23.5, 12.7 ± 1.2, 1445 ± 67.9 and 5.7 ± 0.2 mg/L, respectively as shown in Table 1. The alkaline pH and high EC of collected tannery wastewater could affect the biological

Conclusion

Metals such as chromium, cadmium, mercury, arsenic, lead etc. are considered as a major environmental pollutant due to their toxic effects on environment as well as on human health. Based on the results of this study, it can be concluded that the isolated bacterium can be a good agent for the reduction/detoxification of hexavalent chromium from contaminated environments. During the chromium reduction experiment, the bacterium was found capable to reduce 99.33% and 96.98% Cr(VI) at 50 and 100 

Acknowledgements

Authors are highly grateful to the University Grant Commission (UGC), Government of India (GOI), New Delhi for UGC Fellowship. Authors also acknowledge the support from USIC B. B. Ambedkar University for SEM and FTIR analysis.

References (57)

  • V. Kumari et al.

    Genotoxicity evaluation of tannery effluent treated with newly isolated hexavalent chromium reducing Bacillus cereus

    J. Environ. Manag.

    (2016)
  • Y. Liu et al.

    Cr(Cl) reduction by Bacillus sp. isolated from chromium landfill

    Process. Biochem.

    (2006)
  • D.P. Mungasavalli et al.

    Biosorption of chromium from aqueous solutions by pre-treated Aspergillus niger batch and column studies

    Colloids Surf. A: Physicochem. Eng. Asp.

    (2007)
  • S. Sagar et al.

    Hexavalent chromium reduction and plant growth promotion by Staphylococcus arlettae Strain Cr11

    Chemosphere

    (2012)
  • T. Srinath et al.

    Chromium (VI) biosorption and bioaccumulation by chromate resistant bacteria

    Chemosphere

    (2002)
  • S. Sultan et al.

    Reduction of toxic hexavalent chromium by Ochrobactrum intermedium strain SDCr-5 stimulated by heavy metals

    Bioresour. Technol.

    (2007)
  • U. Thacker et al.

    Hexavalent chromium reduction by Providencia sp

    Process. Biochem.

    (2006)
  • U. Thacker et al.

    Reduction of chromate by cell-free extract of Brucella sp. isolated from Cr(VI) contaminated sites

    Bioresour. Technol.

    (2007)
  • A. Zahoor et al.

    Isolation of Cr(VI) reducing bacteria from industrial effluents and their potential use in bioremediation of chromium containing wastewater

    J. Environ. Sci.

    (2009)
  • J.C. Akan et al.

    Assessment of tannery industrial effluent from Kano metropolis, Nigeria Asian network for Scientific information

    J. Appl. Sci.

    (2007)
  • S.F. Altschul et al.

    Gapped BLAST and PSIBLAST: a new generation of protein database search programs

    Nucleic Acids Res.

    (1997)
  • APHA

    Standard Methods for the Examination of Water and Wastewater

    (2012)
  • G.I. Barrow et al.

    Cowan and Steel's Manual for the Identification of Medical Bacteria

    (1993)
  • A.A. Belay

    Impacts of chromium from tannery effluent and evaluation of alternative treatment options

    J. Environ. Prot.

    (2010)
  • R.N. Bharagava et al.

    Isolation and characterization of aerobic bacteria capable of the degradation of synthetic and natural melanoidins from distillery wastewater

    World J. Microbiol. Biotechnol.

    (2009)
  • R.N. Bharagava et al.

    Antibiotic and heavy metal resistance properties of bacteria isolated from the aeration lagoons of common effluent treatment plant (CETP) of tannery industries (Unnao, India)

    Ind. J. Biotechnol.

    (2014)
  • G. Cabrera et al.

    Bacterial removal of chromium (VI) and (III) in a continuous system

    Biodegradation

    (2007)
  • Central pollution control board (CPCB)

    Pollution Assessment: River Ganga. Status of Grossly Polluting Industries (GPI)

    (2013)
  • Cited by (263)

    View all citing articles on Scopus
    View full text