Azo dye decolorization by halophilic and halotolerant microorganisms

Abstract

Different types of microorganisms are capable of degrading azo dyes due to their high metabolic potentials. However, many of them cannot be used as degrading agents due to the harsh conditions of dyepolluted environments. Here, halophilic and halotolerant microorganisms can be the best candidates for a practical biodecolorization process as they are able to grow easily at high concentrations of salts. In addition, some of them can tolerate the presence of other stress factors such as toxic oxyanions and heavy metals which are so common in industrial wastewaters. In recent years, several studies have been focused on halophilic and halotolerant microorganisms and their abilities for decolorization of azo dyes. For example, Shewanella putrefaciens was determined to be capable of the complete removal of Reactive Black-5, Direct Red-81, Acid Red-88 and Disperse Orange-3 (all 100 mg l −1 ) within 8 h in the presence of 40 g l −1 NaCl. Another halophilic example is Halomonas sp. GTW which has shown a remarkable performance in the removal of different azo dyes within 24 h in the presence of 150 g l −1 NaCl. Although these approaches need to be studied in more detail, some studies have designed different types of fermentation processes and even specific fermentors to provide a practical methodology for industrial wastewater remediation.Sequential anaerobic EGSB (expanded granular sludge blanket) and aerobic reactor was the result of an important attempt to design an effective approach to large-scale biodecolorization.

Biodegradation of Rubine GFL by Galactomyces geotrichum MTCC 1360 and subsequent toxicological analysis by using cytotoxicity, genotoxicity and oxidative stress studies

“…In the last few decades, several physicochemical treatment methods have been developed, including flocculation combined with flotation, electroflocculation, membrane filtration, electrokinetic coagulation, electrochemical destruction, ion-exchange, irradiation, precipitation and ozonation involving the use of activated carbon and air mixtures, but these technologies are generally expensive, are ineffective in colour removal from textile dyestuffs, are not adaptable to a wide range of dye wastewaters, and produce a large amount of sludge or cause secondary pollution due to excessive chemical usage (Joe et al, 2008;Tamboli et al, 2010a;Saratale et al, 2011;Amoozegar et al, 2011). Therefore, there is a need to develop alternative means of dye decolorization.…”

Discoloration of Indigo Carmine Using Aqueous Extracts from Vegetables and Vegetable Residues as Enzyme Sources

“…From the results shown in Table 3, it can be perceived that the enzymes present in the aqueous extract of green pea seeds are able to discolor the dye completely, even in the presence of 10% NaCl. The biocatalytic activity of green pea seeds can be compared to that of halotolerant and halophilic microorganisms that are capable to discolor azo dyes in the presence of 4 to 15% of NaCl [28]. There are some reports about the reduction of the PPO activity in the presence of NaCl [29].…”

Hydrolytic Enzymes in Halophilic Bacteria, Properties and Biotechnological Potential

“…Bioremediation of toxic compounds including organic and inorganic materials, production of haloenzymes, compatible solutes, and other valuable compounds could be valuable in different fi elds of biotechnology and industries (Oren 2002a ;Amoozegar et al 2011Amoozegar et al , 2012Alavi et al 2014 ).…”