Removal of azo dyes from water by sol–gel immobilized Pseudomonas sp.

https://doi.org/10.1016/j.jece.2013.12.003Get rights and content

Highlights

  • Bacteria have been immobilized in silicate pearls without losing their viability or ability to decolorize azo dyes.

  • Immobilized bacteria produced more than seven times higher amounts of extracellular enzymes.

  • The immobilized bacteria was successfully evaluated with repeated-batch decolourization experiments.

  • The decolourization was over 75%, 79% and 83% for remazol black, methyl orange and benzyl orange, respectively.

Abstract

Water pollution control is presently one of the major scientific research areas. Sol–gel immobilized Pseudomonas sp. able to enzymatically reduce azo groups was used for the decolourization of water containing azo dyes. It was observed that immobilized bacteria produced more than seven times higher amounts of extracellular enzymes involved in the biodegradation of azo dyes. The reusability of the immobilized bacteria was successfully evaluated with repeated-batch decolourization experiments. Indeed, after four repeated experiments, the decolourization was over 75%, 79% and 83% for remazol black, methyl orange and benzyl orange, respectively. The herein sol–gel immobilized bacteria offer advantages such as high viable cell densities, high stability and extended reaction times. Thus it would be applied as a cost-effective and efficient treatment to remove dyes from effluents.

Introduction

Water pollution control is presently one of the major scientific research areas. Particularly, colored organic compounds generally represent a minor fraction of the organic components of wastewaters but their color renders them esthetically unacceptable. The color of waste effluents is due to the presence of phenolic compounds such as tannins or lignins (2–3%), organic colorants (3–4%) and especially dyes and dye intermediates [1]. Dyes are difficult to be decolourized due to their complex structure, synthetic origin and recalcitrant nature, which makes it obligatory to remove them from industrial effluents before being disposed into hydrological systems [2]. These dyes include several structural forms such as acidic, reactive, basic, disperse, azo, diazo, anthraquinone based and metal-complex dyes [3]. In this sense, Government legislation imposes strict regulating measures that compel industries to treat their waste effluents to increasingly high quality levels. During the past two decades, several decolourization techniques have been reported, few of which have been accepted by industries. Thus, there is a need to find alternative cost-effective and efficient treatments to remove dyes and colorants from effluents [4]. Among the different methods to treat effluents, the advantage of biological treatments over certain physico chemical treatment methods is that over 70% of the organic material present may be converted to biosolids [5]. In this aspect, numerous bacteria capable of dye decolourization [6], [7], [8], [9] have been reported [10], [11], [12], [13], [14].

Immobilized microorganisms are being increasingly used for wastewater treatment bioreactors as they offer advantages such as high cell densities, high stability, absence of cell washout, and extended reaction times [15]. Among the different immobilization techniques, sol–gel chemistry is an interesting domain because it allows obtaining materials with desirable new chemical and mechanical properties [16], [17]. Moreover, it was early identified as an eco-friendly process compared to traditional synthesis routes to ceramics and glasses, thus improving sustainability in product developments [18]. During the last 15 years several works reported the encapsulation of living cells in sol–gel silica matrices [19], [20], [21], [22], [23]. Indeed, since Carturan et al. [24] pioneered the encapsulation of living microorganisms in sol–gel silica matrices several works were reported extending the process to other cell types [25], [26] such us bacteria, yeast, algae and mammalian cells which were successfully immobilized in silica matrices [27], [28], [29], [30], [31], [32]. In most cases it was demonstrated that the employment of biocompatible molecules such as glycerol, polyethylene glycol or glycine betaine further improve the biocompatibility of the immobilization process [33], [34], [35], [36], [37].

Nowadays, this technology is well established for the development of immobilization matrices and its application in different processes is growing fast. Particularly, the immobilization of bacteria in sol–gel matrices for environmental biotechnological processes constitutes an active area of research [38], [39], [40], [41], [42], [43], [44], [45], [46]. Especially, because it will allow using them in environments that are normally hostile to biosystems [47], [48]. Herein we report the immobilization of Pseudomonas sp. in sol–gel silica matrices and its application for water treatment. Indeed, the immobilized bacteria were successfully applied to decolorize remazol black (RB), methyl orange (MO) and benzyl orange (BO), which are azo dyes commonly used in industrial processes. To the best of our knowledge, it is the first time that sol–gel immobilized Pseudomonas sp. with excellent decolorizing ability against azo dyes has been reported.

Section snippets

Bacterial strains, culture conditions, and viability determination

Pseudomonas sp. was gently provided by the Higiene y Sanidad group from the Microbial Culture Collection of Facultad de Farmacia y Bioquimica (CCM 29), University of Buenos Aires, Argentina. Cells were grown for 24 h at 35 °C and maintained in Luria–Bertani (LB) medium (yeast extract, 5 g l−1; NaCl, 10 g l−1 and tryptone, 10 g l−1) up to OD (600 nm) 0.800, centrifuged and resuspended in LB medium. The number of colony-forming units (cfu) per milliliter of this suspension was determined by the plate

Activity of extracellular enzymes

Microbial extracellular enzymes have a potential to degrade a wide range of complex aromatic dyestuffs. Thus, the analysis of the activity and release of these enzymes from immobilized bacteria is highly important when foreseeing industrial applications. In this sense, the activity of laccase, tyrosinase, azoreductase and lignin peroxidase were measured in supernatants of free and immobilized bacteria cultures in the presence of the dye. It was observed that the activity of the enzymes lignin

Conclusions

Herein, bacteria have been immobilized in silicate pearls without losing their viability or ability to decolorize the three dyes assayed. In comparison with other cells, soil bacteria survive best sol–gel process of encapsulation into silica gels [57], [58]. Moreover, immobilized bacteria have gained certain advantages. One important advantage of the herein presented biodegradation system is the production of higher levels of extracellular enzymes involved in the biodegradation of the dyes.

Acknowledgements

The authors would like to acknowledge the support of grants from the University of Buenos Aires UBACYT B049 (to L.E.D.) and 20020090200051 (to M.F.D.) and from Agencia Nacional de Investigaciones Científicas y Técnicas PICT 2012-1441.

References (58)

  • M. Gou et al.

    Azo dye decolorization by a new fungal isolate, Penicillium sp. QQ and fungal-bacterial cocultures

    Journal of Hazardous Materials

    (2009)
  • O. Anjaneya et al.

    Decolorization of sulfonated azo dye Metanil Yellow by newly isolated bacterial strains: Bacillus sp. strain AK1 and Lysinibacillus sp. strain AK2

    Journal of Hazardous Materials

    (2011)
  • G. Carturan et al.

    Inorganic gels for immobilization of biocatalysts: inclusion of invertase-active whole cells of yeast (Saccharomyces cerevisiae) into thin layers of SiO2 gel deposited on glass sheets

    Journal of Molecular Catalysis

    (1989)
  • C.F. Meunier et al.

    Encapsulation of cells within silica matrixes: towards a new advance in the conception of living hybrid materials

    Journal of Colloid and Interface Science

    (2010)
  • A. Nieto et al.

    Cell viability in a wet silica gel

    Acta Biomaterialia

    (2009)
  • A. Pannier et al.

    Biodegradation of fuel oxygenates by sol–gel immobilized bacteria Aquincola tertiaricarbonis L108

    Enzyme and Microbial Technology

    (2010)
  • M. Al-Saraj et al.

    Bioaccumulation of some hazardous metals by sol–gel entrapped microorganisms

    Journal of Non-Crystalline Solids

    (1999)
  • N. Hatvani et al.

    Production of laccase and manganese peroxidase by Lentinus edodes on malt-containing by-product of the brewing process

    Process Biochemistry

    (2001)
  • Y. Anjaneyulu et al.

    Decolourization of industrial effluents – Available methods and emerging technologies – A review

    Reviews in Environmental Science and Biotechnology

    (2005)
  • C. Raghavacharya

    Colour removal from industrial effluents

    Chemical Engineering World

    (1997)
  • K.E. Stormo et al.

    Preparation of encapsulated microbial cells for environmental applications

    Applied and Environmental Microbiology

    (1992)
  • C. Brinker et al.

    Sol-Gel Science

    (1990)
  • R. Iler

    The Chemistry of Silica

    (1979)
  • N. Baccile et al.

    Introducing ecodesign in silica sol–gel materials

    Journal of Materials Chemistry

    (2009)
  • D. Avnir et al.

    Recent bio-applications of sol–gel materials

    Journal of Materials Chemistry

    (2006)
  • T. Coradin et al.

    Sol–gel biopolymer/silica nanocomposites in biotechnology

    Current Nanoscience

    (2006)
  • M.F. Desimone et al.

    Development of sol–gel hybrid materials for whole cell immobilization

    Recent Patents on Biotechnology

    (2009)
  • A. Léonard et al.

    Whole-cell based hybrid materials for green energy production, environmental remediation and smart cell-therapy

    Chemical Society Reviews

    (2011)
  • J. Livage et al.

    Living cells in oxide glasses

    Reviews in Mineralogy and Geochemistry

    (2006)
  • Cited by (40)

    • Immobilization of microbes and enzymes for textile wastewater treatment

      2023, Current Developments in Bioengineering and Biotechnology: Advances in Eco-friendly and Sustainable Technologies for the Treatment of Textile Wastewater
    • Ionic liquids as extraction solvents for removal of dyes

      2021, Ionic Liquid-Based Technologies for Environmental Sustainability
    View all citing articles on Scopus
    View full text