Microbial diversity, transformation and toxicity of azo dye biodegradation using thermo-alkaliphilic microbial consortia.

In this research, the transformation and toxicity of Reactive Red 141 and 239 biodegraded under anaerobic-aerobic conditions as well as metagenomic analysis of Reactive Red 239 degrading microbial consortia collected from Shala Hot spring were investigated. Toxicity of dyes before treatment and after treatment on three plants, fish and microorganisms were done. A halotolerant and thermo-alkaliphilic bacterial consortia decolorizing azo dyes (>98% RR 141 and > 96% RR 239 in 7 h) under optimum conditions of salt concentration (0.5%), temperature (55 °C) and pH (9), were used. Toxicity effect of untreated dyes and treated dyes in Tomato > Beetroot > Cabbage plants, while the effect was Leuconostoc mesenteroides > Lactobacillus plantarum > Escherichia coli in microorganisms. Among fishes, the toxicity effect was highest in Oreochromis niloticus followed by Cyprinus carpio and Clarias gariepinus. The three most dominant phyla that could be in charge of decolorizing RR 239 under anaerobic-aerobic systems were Bacteroidota (22.6-29.0%), Proteobacteria (13.5-29.0%), and Chloroflexi (8.8-23.5%). At class level microbial community structure determination, Bacteroidia (18.9-27.2%), Gammaproteobacteria (11.0-15.8%), Alphaproteobacteria (2.5-5.0%) and Anaerolineae (17.0-21.9%) were dominant classes. The transformation of RR 141 and RR 239 into amine compounds were proposed via high performance liquid chromatography-mass spectroscopy (HPLC/MS) and fourier transform infrared spectroscopy (FT-IR). Overall, dye containing wastewaters treated under anaerobic-aerobic systems using thermo-alkaliphilic microbial consortia were found to be safe to agricultural (fishes and vegetables) purposes.

Evaluating the potential of thermo-alkaliphilic microbial consortia for azo dye biodegradation under anaerobic-aerobic conditions: Optimization and microbial diversity analysis.

Wastewaters in textile industry are mainly characterized by higher pH, color, salt and chemical oxygen demand (COD) values, which are environmentally undesirable. Among these textile effluent characteristics, color removal is the most challenging task. In this study, the potential of Rift Valley halotolerant and thermo-alkaliphilic microbial consortia (collected from Shala hot spring located in Ethiopia) for azo dye biodegradation under anaerobic-aerobic conditions were evaluated. Optimization and microbial diversity analysis were done using Reactive Red 141. Under optimum conditions of pH (9), temperature (55 °C), salinity (0.5%), and nutrients, microbial consortia can remove >98% color and 92.7 ± 7.3% COD under anaerobic and aerobic conditions, respectively. In addition, the consortia was capable of decolorizing initial dye concentrations of 100-1000 mg/L, and various dye types including Everzol Blue LX, RY 84, RR 239, RB 198 and RY 700. The 16S rRNA gene sequence results showed that Bacteroidetes (25.3%) > Proteobacteria (21.0%) > Chloroflexi (18.5%) > Halobacterota (6.2%) dominant phyla. Based on the findings, non-color effluent adapted Rift Valley halotolerant and thermo-alkaliphilic bacterial consortia can be a potential candidate for bioremediation of textile and other industries characterized by higher salinity, temperature and pH.

Biodecolorization of textile azo dye using Bacillus sp. strain CH12 isolated from alkaline lake.

Textile azo dye decolorizing bacteria were isolated from alkaline Lakes Abaya and Chamo using Reactive Red 239 (RR239) dye. Through subsequent screening process, strain CH12 was selected to investigate the effects of nutrient supplement, DO, pH, temperature, dye concentration and types on decolorization. Based on 16S rRNA gene sequence analysis, strain CH12 was identified as Bacillus sp. Decolorization efficiencies were significantly enhanced with carbon (≥98%) and organic nitrogen (∼100%) supplements. Complete decolorization was also observed under anoxic and anaerobic conditions, and at the temperature of 30 °C and the pH of 10. However, the azo dye decolorization efficiency of strain CH12 was significantly reduced when NaNO3 (1-8%) was supplemented or under aerobic culturing condition (≤6%), indicating that RR239 was less preferred electron acceptor. Overall, strain CH12 can be a promising candidate for decolorization applications due to its potential to effectively decolorize higher RR239 concentrations (50-250 mg/L) and six additional dyes.