Isolation and characterization of a lead (Pb) tolerant Pseudomonas aeruginosa strain HF5 for decolorization of reactive red-120 and other azo dyes

Diesel degradation capability and environmental robustness of strain Pseudomonas aeruginosa WS02

Petroleum hydrocarbon (PHC) degrading bacteria have been frequently discovered. However, in practical application, a single species of PHC degrading bacterium with weak competitiveness may face environmental pressure and competitive exclusion due to the interspecific competition between petroleum-degrading bacteria as well as indigenous microbiota in soil, leading to a reduced efficacy or even malfunction. In this study, the diesel degradation ability and environmental robustness of an endophytic strain Pseudomonas aeruginosa WS02, were investigated. The results show that the cell membrane surface of WS02 was highly hydrophobic, and the strain secreted glycolipid surfactants. Genetic analysis results revealed that WS02 contained multiple metabolic systems and PHC degradation-related genes, indicating that this strain theoretically possesses the capability of oxidizing both alkanes and aromatic hydrocarbons. Gene annotation also showed many targets which coded for heavy metal resistant and metal transporter proteins. The gene annotation-based inference was confirmed by the experimental results: GC-MS analysis revealed that short chain PHCs (C10-C14) were completely degraded, and the degradation of PHCs ranging from C15-C22 were above 90% after 14 d in diesel-exposed culture; Heavy metal (Mn2+, Pb2+ and Zn2+) exposure was found to affect the growth of WS02 to some extent, but not its ability to degrade diesel, and the degradation efficiency was still maintained at 39-59%. WS02 also showed a environmental robustness along with PHC-degradation performance in the co-culture system with other bacterial strains as well as in the co-cultured system with the indigenous microbiota in soil fluid extracted from a PHC-contaminated site. It can be concluded that the broad-spectrum diesel degradation efficacy and great environmental robustness give P. aeruginosa WS02 great potential for application in the remediation of PHC-contaminated soil.

Decolorization of Reactive Red 120 by a novel bacterial consortium: Kinetics and heavy metal inhibition study

<abstract><p>Juru River is one of the most polluted rivers in Malaysia. A dye-degrading bacterial consortium has been isolated from the river's sediment. This consortium JR3 consists of <italic>Pseudomonas aeruginosa</italic> MM01, <italic>Enterobacter</italic> sp. MM05 and <italic>Serratia marcescens</italic> MM06, which were able to decolorize up to 700 ppm of the Reactive Red 120 (RR120) dye under optimal conditions with limited substrate available. Substrate inhibition kinetics were investigated, and, based on the best model, Aiba, the maximum growth rate was 0.795 h^–1, while the saturation constant and inhibitory constant were 0.185% and 0.14%, respectively. In addition, the influence of various metal ions on the growth and decolorization rate of this bacterial consortium on RR120 was investigated. Chromium showed the weakest effect on the decolorization of 200 ppm RR120, with 73.5% removal and bacterial growth of 11.461 log CFU mL^–1. Zinc yielded the second weakest effect, followed by silver and lead, with percentages of RR120 decolorization of 63.8%, 54.6% and 50.5%, respectively. Meanwhile, cadmium, arsenic and copper reduced the decolorization of RR120 in consortium JR3 by half. Mercury strongly inhibited decolorization by 32.5%. Based on the least inhibited heavy metal in RR120 decolorization activity of consortium JR3, the best inhibitory kinetic model was Levenspiel, with a maximum growth rate of 0.632 h^–1, while the saturation constant and inhibitory constants were 15.08% and 0.5783%, respectively. The metal-tolerant azo dye-degrading bacterial consortium will be very useful in dye remediation in metal-laden polluted environments.</p></abstract>

Noval porous phosphate-solubilizing bacteria beads loaded with BC/nZVI enhanced the transformation of lead fractions and its microecological regulation mechanism in soil

Soil lead pollution becomes a serious environmental problem. Microbial remediation has received widespread attentions due to high efficiency and no secondary pollution. In this research, a noval porous spherical phosphate-solubilizing bacteria bead loaded with biochar/nZVI (Bio-bead) was used to passivate lead in soil, and the effects and microecological regulation mechanisms of this process were also investigated. The results showed that the pH, OM, and AP of soil in the Bio-bead group were increased and the ORP was decreased over time compared with the blank group. The proportion of stable (oxidizable and residue) fractions of lead in Bio-bead group (45%) was much higher than that of the blank group (35%). In addition, the result of microbial community structure showed that Bio-beads did not change the species of dominant bacterial, excepting the abundance of Pseudomonas increased significantly and the abundance of Sphingomonas reduced during remediation. Redundancy analysis showed that pH, OM, AP and the ratio of residual and oxidizable fractions lead in soil were positively correlated with the abundance of Pseudomonas, while ORP was negatively correlated with the abundance of Pseudomonas. These findings have proved that Bio-bead is a potential strategy for remediation of lead-contaminated soil even in complexed soils.

Biodegradation of Brown 706 Dye by Bacterial Strain Pseudomonas aeruginosa

Dyes are the most challenging pollutants for the aquatic environment that are not only toxic, but also interfering photosynthesis as light penetration into deep water is changed. A number of methods are used for the water reclamation, however, among them biological methods are preferably used due to their compatibility with nature. In the present research, 15 different bacterial strains were used to decolorize Brown 706 dye. Among the bacterial strains, Pseudomonas aeruginosa showed maximum decolorization activity; hence in the subsequent experiments Pseudomonas aeruginosa was used. First the decolorization activities were carried out under different physicochemical conditions to obtain the optimum decolorization benefits of the selected microorganism. The optimum conditions established were 37°C, pH of 7 and operation cycle time 72 h. In the subsequent experiment all optimum conditions were combined in a single experiment where 73.91% of decolorization efficiency was achieved. For the evaluation of metabolites formed after decolorization/degradation the aliquots containing bacteria were homogenized, filtered and then subjected to extraction. The extracted metabolites were then subjected to the silica gel column isolation. UV–Vis, FTIR, and NMR techniques were used to elucidate structures of the metabolites. Out of the collected metabolites only P-xylene was identified, which has been formed by cleavage of azo linkage by azo reductase enzyme of bacteria following the deamination and methylation of nitro substituted benzene ring.

Biodecolourisation of Reactive Red 120 as a Sole Carbon Source by a Bacterial Consortium-Toxicity Assessment and Statistical Optimisation

The application of microorganisms in azo dye remediation has gained significant attention, leading to various published studies reporting different methods for obtaining the best dye decolouriser. This paper investigates and compares the role of methods and media used in obtaining a bacterial consortium capable of decolourising azo dye as the sole carbon source, which is extremely rare to find. It was demonstrated that a prolonged acclimation under low substrate availability successfully isolated a novel consortium capable of utilising Reactive Red 120 dye as a sole carbon source in aerobic conditions. This consortium, known as JR3, consists of Pseudomonas aeruginosa strain MM01, Enterobacter sp. strain MM05 and Serratia marcescens strain MM06. Decolourised metabolites of consortium JR3 showed an improvement in mung bean's seed germination and shoot and root length. One-factor-at-time optimisation characterisation showed maximal of 82.9% decolourisation at 0.7 g/L ammonium sulphate, pH 8, 35 °C, and RR120 concentrations of 200 ppm. Decolourisation modelling utilising response surface methodology (RSM) successfully improved decolourisation even more. RSM resulted in maximal decolourisation of 92.79% using 0.645 g/L ammonium sulphate, pH 8.29, 34.5 °C and 200 ppm RR120.

Biodegradation and biosorption of Reactive Red 120 dye by immobilized Pseudomonas guariconensis: Kinetic and toxicity study

Reactive dyes are pernicious pollutants in textile effluent, which are to be treated passably before discharging into the environment. In the present study, a potential dye degrading bacterial strain Pseudomonas guariconensis was isolated from paddy rhizosphere and was characterized by 16S rRNA gene sequencing. The biodegradation ability of the strain was evaluated by time-based study with immobilized bacterial cells in calcium alginate biocarrier matrix and also with free cells. The results indicated that the strain exhibited maximum degradation of 91% when immobilized in the biocarrier matrix. The enzymatic study revealed the production of oxidoreductase enzymes. The degraded products were identified as 2-amino-3-phenylpropanoic acid and benzoquinone by gas chromatography-mass spectroscopy (GC-MS) analysis, and a degradative pathway was derived based on the enzymatic profile. A packed bed column was designed using P. guariconensis VITSAJ5 immobilized in calcium alginate beads as a biosorbent for the removal of Reactive Red 120. The immobilized bacterial cells exhibited 87% uptake of RR120, whereas the nonimmobilized bacterial cells exhibited a maximum uptake of 37%. The phytotoxicity analysis by seed germination assay revealed an enhanced plumule and radicle length, indicating the nontoxic byproducts after the treatment of Reactive Red 120 by VITSAJ5 compared to the untreated Reactive Red 120 solution. PRACTITIONER POINTS: Current study is the first report on Pseudomonas guariconensis capable of degrading reactive dyes (Reactive Red 120) It was observed that the degradation potential was maximum when cells were immobilized with Ca-Ag biocarrier matrix Breakdown metabolism of Reactive Red 120 was derived through pathway prediction Employing immobilized bacteria in a packed bed column found to possess a prominent biosorption ability on the matrix enhancing the degradation process Toxic reactive dye was converted into nontoxic compounds, evidenced by phytotoxicity studies.

Bacillus firmus strain FSS2C ameliorated oxidative stress in wheat plants induced by azo dye (reactive black-5)

This study was conducted to determine the ability of a bacterial strain FSS2C to ameliorate growth of wheat plants grown under induced stress of reactive black-5 (RB-5). The strain was taxonomically identified as Bacillus firmus on the basis of its 16S rRNA gene sequence analysis. The B. firmus FSS2C was found physiologically potent in phosphate solubilization, indole-3-acetic acid production and ammonia synthesis in the presence of varying concentrations of azo dye RB-5. Moreover, it decolorized RB-5 in vitro with the maximum decolorization (%) found at pH 7 and 30 °C. Inoculation of wheat plants, growing under stress induced by RB-5 dye, with rifampicin-resistant derivatives of the strain FSS2C substantially reduced the cellular oxidative stress, thereby resulting in higher plant biomass as compared to non-inoculated plants. Similarly, the inoculated plants revealed higher nutrient content in shoots as compared to non-inoculated ones. It was concluded that B. firmus strain FSS2C alleviated the oxidative stress impairment caused by reactive black-5 in wheat plants. Therefore, the strain can be used as bio-inoculant in wastewater irrigated soils.