Economical and bio-friendly approaches are needed to remediate dye-contaminated wastewater from various industries. In this study, a novel bacterial strain capable of decolorizing triarylmethane dyes was isolated from a textile wastewater treatment plant in Greece. The bacterial isolate was identified as Aeromonas hydrophila and was shown to decolorize three triarylmethane dyes tested within 24 h with color removal in the range of 72% to 96%. Decolorization efficiency of the bacterium was a function of operational parameters (aeration, dye concentration, temperature, and pH) and the optimal operational conditions obtained for decolorization of the dyes were: pH 7-8, 35°C and culture agitation. Effective color removal within 24 h was obtained at a maximum dye concentration of 50 mg/L. Dye decolorization was monitored using a scanning UV/visible spectrophotometer which indicated that decolorization was due to the degradation of dyes into non-colored intermediates. Phytotoxicity studies carried out using Triticum aestivum, Hordeum vulgare, and Lens esculenta revealed the triarylmethane dyes exerted toxic effects on plant growth parameters monitored. However, significant reduction in toxicity was obtained with the decolorized dye metabolites thus, indicating the detoxification of the dyes following degradation by Aeromonas hydrophila.
This study was carried out to evaluate the biostimulant potentials of Capra aegagrus hircus manure for bioremediation of crude oil contaminated soil (COCS) under tropical conditions. 1 kg of COCS sample was amended with 0.02 kg of C. a. hircus manure and monitored at 14-day intervals for total petroleum hydrocarbon (TPH), nutrient content, and changes in microbial counts. At the end of the study period, there was 62.08% decrease in the concentration of TPH in the amended sample compared to 8.15% decrease in the unamended sample, with significant differences (P < 0.05) in TPH concentrations for both samples at different time intervals. Similarly, there was a gradual decrease in the concentrations of total organic carbon, nitrogen, phosphorus, and potassium in both samples. The culturable hydrocarbon-utilizing bacteria (CHUB) increased steadily from 8.5 × 105 cfu/g to 2.70 × 106 cfu/g and from 8.0 × 105 cfu/g to 1.78 × 106 cfu/g for both samples. Acinetobacter, Achromobacter, Bacillus, Flavobacterium, Klebsiella, Micrococcus, Pseudomonas, and Staphylococcus were isolated from amended sample with Pseudomonas being the predominant isolated bacterial genus. This study demonstrated that C. a. hircus manure is a good biostimulant, which enhanced the activities of indigenous hydrocarbonoclastic bacteria resulting in significant decrease in TPH concentration of COCS.
The decolorization and degradation of Direct Blue 71 were investigated using a mono culture of Pseudomonas aeruginosa. The bacterium was able to decolorize the dye medium to 70.43 % within 48 h under microaerophilic conditions. The medium was then aerated for 24 h to promote the biodegradation of the aromatic amines generated from azo bond cleavage. Reduction in total organic carbon in dye medium was 42.58 % in the microaerophilic stage and 78.39 % in the aerobic stage. The degradation metabolites formed were studied using UV–vis techniques, high performance liquid chromatography, Fourier transform infra red spectroscopy and nuclear magnetic resonance spectroscopy analysis. Data obtained provide evidence for the formation of aromatic amines and their subsequent oxidative biodegradation by a single strain of P. aeruginosa during successive microaerophilic/aerobic stages in the same flask. The influence of incubation temperature (20–45 °C), medium pH (5–10) and initial dye concentration (25–150 mg/L) on decolorization was evaluated to greatly influence decolorization extent. The optimal decolorization conditions were determined by response surface methodology based on three-variable central composite design to obtain maximum decolorization and to determine the significance and interaction effect of the variables on decolorization. The optimal conditions of response were found to be 35.15 °C, pH 8.01 and 49.95 mg/L dye concentration giving an experimental decolorization value of 84.80 %. Very high regression coefficient between the variables and the response (R2 = 0.9624) indicated a good evaluation of experimental data by polynomial regression model.
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