Removal of azo dyes from water by sol–gel immobilized Pseudomonas sp.
Graphical abstract
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)
Effects of colorants in the aquatic environment
Ecotoxicology and Environmental Safety
(1987)- et al.
Remediation of dyes in textile effluent: a critical review on current treatment technologies with a proposed alternative
Bioresource Technology
(2001) - et al.
Developments in microbial methods for the treatment of dye effluents
Advances in Applied Microbiology
(2004) - et al.
Microbial decolorization of textile-dye-containing effluents: a review
Bioresource Technology
(1996) - et al.
Fungal dye decolourization: recent advances and future potential
Environment International
(2009) - et al.
Bacterial decolorization and degradation of azo dyes
International Biodeterioration and Biodegradation
(2007) Dye removal by immobilised fungi
Biotechnology Advances
(2009)- et al.
Aerobic decolorization and degradation of Acid Red B by a newly isolated Pichia sp. TCL
Journal of Hazardous Materials
(2012) - et al.
Decolorization and degradation of azo dye Reactive Violet 5R by an acclimatized indigenous bacterial mixed cultures-SB4 isolated from anthropogenic dye contaminated soil
Journal of Hazardous Materials
(2012) - et al.
Degradation of estrogens by laccase from Myceliophthora thermophila in fed-batch and enzymatic membrane reactors
Journal of Hazardous Materials
(2012)
Azo dye decolorization by a new fungal isolate, Penicillium sp. QQ and fungal-bacterial cocultures
Journal of Hazardous Materials
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
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
Encapsulation of cells within silica matrixes: towards a new advance in the conception of living hybrid materials
Journal of Colloid and Interface Science
Cell viability in a wet silica gel
Acta Biomaterialia
Biodegradation of fuel oxygenates by sol–gel immobilized bacteria Aquincola tertiaricarbonis L108
Enzyme and Microbial Technology
Bioaccumulation of some hazardous metals by sol–gel entrapped microorganisms
Journal of Non-Crystalline Solids
Production of laccase and manganese peroxidase by Lentinus edodes on malt-containing by-product of the brewing process
Process Biochemistry
Decolourization of industrial effluents – Available methods and emerging technologies – A review
Reviews in Environmental Science and Biotechnology
Colour removal from industrial effluents
Chemical Engineering World
Preparation of encapsulated microbial cells for environmental applications
Applied and Environmental Microbiology
Sol-Gel Science
The Chemistry of Silica
Introducing ecodesign in silica sol–gel materials
Journal of Materials Chemistry
Recent bio-applications of sol–gel materials
Journal of Materials Chemistry
Sol–gel biopolymer/silica nanocomposites in biotechnology
Current Nanoscience
Development of sol–gel hybrid materials for whole cell immobilization
Recent Patents on Biotechnology
Whole-cell based hybrid materials for green energy production, environmental remediation and smart cell-therapy
Chemical Society Reviews
Living cells in oxide glasses
Reviews in Mineralogy and Geochemistry
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