Biodegradation of high concentration of nitrobenzene by Pseudomonas corrugata embedded in peat-phosphate esterified polyvinyl alcohol

Efficiency on biodegradation of high concentration of nitrobenzene (NB) by peat-phosphate esterified polyvinyl alcohol-embedded NB-degrading bacteria Pseudomonas corrugata was conducted compared to free bacteria cells. Its biodegradation kinetics, reuse ability, degradation effect in the absence of the essential element needed for the growth of bacteria and degradation efficiency of the raw water from the contaminated site were also invested. Results show that the degradation rate when the concentration of NB was at 600, 750, and 900 mg/L reached 91.02, 83.23, and 55.9 %, which was higher than that observed in free bacteria at the same concentration levels. Biodegradation kinetics of the material could be well described by first- and zero-order kinetics when the concentration of NB was at 300, 450 mg/L and 600, 750, 900 mg/L, respectively. Stable degradation activity (stayed at a level of approximately 70 %) was displayed during the 11th repeat-batch experiment. The affect of absence of phosphorus in the medium can be abated ascribed to the addition of peat, which contributes with organic matter and other elements such as nitrogen and phosphorus necessary to maintain metabolically active the microorganisms. Effective biodegradation of the raw water from the experimental site revealed that the material can be a potential candidate for treating NB-contaminated wastewater in the practical setting.     

裂褶菌cfcc7252菌株对孔雀石绿染料的高效降解

【目的】评价裂褶菌cfcc7252菌株降解孔雀石绿(Malachite Green,MG)的能力及其潜在的应用价值。【方法】采用单因子液体培养实验,研究了通气、p H、温度、碳源和氮源种类及浓度、金属离子、盐度、染料浓度对该菌降解效果的影响;采用平皿培养实验,利用植物种子萌发和微生物抑菌实验对降解产物进行毒性测试。【结果】研究结果表明,裂褶菌cfcc7252菌株在好氧和厌氧条件下均能高效降解MG。该菌在10.0 g/L葡萄糖,5.0 g/L酵母浸粉,0.01 mmol/L Zn2+,p H为4.0的液体培养基中培养36 h,对350 mg/L的MG降解率达67.8%;连续降解7次后,其降解率还能保持在95.4%以上。此外,该菌在盐度低于10.20%时,其对MG的降解率均达到98%以上。对植物、微生物的毒性测试结果表明,MG降解产物对红豆、豌豆等植物、金黄色葡萄球菌、枯草芽孢杆菌和铜绿假单胞杆菌等微生物基本没有毒性。【结论】裂褶菌cfcc7252菌株在处理以MG为主的染料废水时具有很强的应用潜力。     

Decolorization of chemically different dyes by white-rot fungi in submerged cultures

Forty-two white-rot fungi in submerged cultures were tested to determine their dye decolorization capacity and the optimal conditions for the decolorization process. Trametes pubescens Cui 7571 was found to be the most effective strain in terms of decolorization performance on the azo dye Congo Red, and it exhibited excellent reusability as well as persistence in sequential decolorization experiments. Optimization of the decoloration process was also conducted to evaluate the effects of a number of chemical compounds, metal salts, inducers, and mediators on the dye decolorization rate. On the seventh day, a highest dye removal of 98.83 % was observed with addition of copper at 2.5 mmol L^?1, Tween 80 at 1.0 % (v/v), and ferulic acid at 0.50 μmol L^?1, respectively. The adsorption of mycelia to dyes was not a significant contributor to dye removal, and decolorization by the functional fungus T. pubescens depended on biodegradation by enzymes, as evidenced by the results of the moist heat sterilization treatment (121°C for 20 min), induction of extracellular enzymes, and scanning electron microscopy. Four dye degradation metabolites, i.e., naphthalene amine, biphenyl amine, biphenyl ,and naphthalene diazonium, were identified by Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry. The phytotoxicity tests indicated that degraded metabolites had almost a negligible effect on the plant seeds as compared to that of dye, which is indicative of the less toxic nature of the metabolites. Our results suggest that white-rot fungus T. pubescens could be developed into a novel azo dye bioremediation strategy.     

Degradation of Sulphonated Azo Dye Red HE7B by Bacillus sp. and Elucidation of Degradative Pathways

Bacteria capable of degrading the sulfonated azo dye Red HE7B were isolated from textile mill effluent contaminated soil. The most efficient isolate was identified as Bacillus sp. Azo1 and the isolate could successfully decolorize up to 89 % of the dye. The decolorized cultural extract analyzed by HPLC confirmed degradation. Enzymatic analysis showed twofold and fourfold increase in the activity of azoreductase and laccase enzymes, respectively, indicating involvement of both reductive and oxidative enzymes in biodegradation of Red HE7B. Degraded products which were identified by GC/MS analysis included various metabolites like 8-nitroso 1-naphthol, 2-diazonium naphthalene. Mono azo dye intermediate was initially generated from the parent molecule. This mono azo dye was further degraded by the organism, into additional products, depending on the site of cleavage of R–N=N–R molecule. Based on the degradation products identified, three different pathways have been proposed. The mechanism of degradation in two of these pathways is different from that of the previously reported pathway for azo dye degradation. This is the first report of a microbial isolate following multiple pathways for azo dye degradation. Azo dye Red HE7B was observed to be phytotoxic, leading to decrease in root development, shoot length and seedling fresh weight. However, after biotreatment the resulting degradation products were non-phytotoxic.     

Cometabolic Degradation of Trichloroethylene by Single- and Two-Phase Systems

The cometabolic degradation of trichloroethylene (TCE) by Pseudomonas putida F1 (strain ATCC 700007) at different concentrations was studied in single- and two-phase systems using 2-undecanone as the second organic phase. Toluene vapors were used as the primary growth substrate for Pseudomonas putida F1. The effects of the biomass concentration and the phase ratio on the biodegradation process were investigated. The best biomass concentration and the most suitable phase ratio were found to be 0.462 and 0.025 g/L (v_org/v_aq), respectively. In the single-phase system, 36.5 mg/L TCE was degraded completely in 15 hours and only 78% of 55 mg/L TCE was degraded in 27 hours, while in the two-phase system 55 mg/L TCE was degraded completely in 14 hours. The use of the two-phase system not only decreased the biodegradation time of TCE but also prevented the inhibition effect of high concentrations of TCE on the microbial biomass.     

Biodegradation of triphenylmethane dye Malachite Green by <Emphasis Type="Italic">Sphingomonas paucimobilis</Emphasis>

Triphenylmethane dyes belong to the most important group of synthetic colorants and are used extensively in the textile industries for dying cotton, wool, silk, nylon, etc. They are generally considered as the xenobiotic compounds, which are very recalcitrant to biodegradation. Sphingomonas paucimobilis, was isolated from the soil sample collected from contaminated sites of textile industry located in KsarHellal, Tunisia, and it was able to decolorize Malachite Green (MG) dye (50 mg/l) within 4 h under shaking condition (pH 9 and temperature 25°C). The effect of inoculum size, dye concentration, temperature and initial pH of the solution were studied. The results obtained from the batch experiments revealed the ability of the tested bacteria to remove dye. UV–Vis spectroscopy and FTIR analysis of samples before and after decolorization confirmed the ability of the tested strain to decolorize MG. In addition, the phytotoxicity study revealed the degradation of MG into non-toxic product by S. paucimobilis.     

Biochemical and Biophysical Response to Calcium Chloride Stress in Aspergillus niger and its Role in Malachite Green Degradation

Filamentous fungi show great promise in remediation of environmental contaminants such as industrial dyes. In the current study, Aspergillus niger (Genbank ID: JF437542) decolorized 82 % of the test dye malachite green (MG; 50 mg/l) during cultivation for 24 h. The organism decolorized only 6 % of the MG at higher concentration (250 mg MG/l) during the same time period and growth was inhibited at this higher MG concentration. Exposing A. niger to different types of stress resulted in variable impacts on ability to decolorize MG. CaCl₂ had the largest positive impact on decolorization. A. niger cultures treated with CaCl₂ (1 M) decolorized 46 % of the MG (250 mg/l) in 1 h compared to 6 % in untreated control cultures. CaCl₂ also increased catalase production in A. niger which strongly supported a direct relationship between stress response and decolorizing ability. Spectrophotometric measurement confirmed MG decolorization while Fourier transform infrared spectroscopy suggested that biodegradation of MG occurred. Cultures treated with CaCl₂ accumulated fewer toxic MG by-products than untreated cultures. CaCl₂-induced stress increased the permeability and conductivity of the fungal cell membrane. An observed increase in medium [H⁺] also suggested a change in Ca²⁺/H⁺ exchange capacity in the fungal cell. Calcium ions had a pronounced effect on membrane properties and this may have had an important impact on signal transduction. We conclude that A. niger decolorizes MG and that CaCl₂ enhances this process; the CaCl₂ effect appears to be associated with stress response.     

Isolation,selection, and biological characterization research of highly effective electricigens from MFCs for phenol degradation

The microbial fuel cells (MFCs) are recognized to be highly effective for the biodegradation of phenol. For isolating the phenol-degrading bacteria, the sample containing 500 mg/L phenol was collected from the MFCs. The strain (WL027) was identified basing on the 16S rRNA gene analysis and phylogenetic analysis as Bacillus cereus. The effects of pH, temperature, concentrations of phenol, heavy metal ions, and salt on the growth of strain as well as the degradation of phenol have been carefully studied. The WL027-strain exhibited favorable tolerance for the metal cations including Cr²⁺, Co²⁺, Pb²⁺, and Cu²⁺ with the concentration of 0.2 mg/L and NaCl solution with a high concentration of 30 g/L. In 41 h, 86.44% of 500 mg/L phenol has been degraded at the initial pH at 6 and the temperature of 30 °C. The strain was highly active electrogenesis bacteria and the coulombic efficiency reached 64.25%, which showed significant advantage on the efficient energy conversion. Therefore, due to the highly efficient degradation of phenol, WL027-strain could be used in the treatment of phenol-containing wastewater.     

Biodegradation of methidathion by Serratia sp. in pure cultures using an orthogonal experiment design, and its application in detoxification of the insecticide on crops

An enrichment culture method was applied to the isolation of a bacterial strain responsible for biodegradation of methidathion residues, from a methidathion-treated orchard. The strain (SPL-2) was identified as Serratia sp. according to its physiological characteristics and 16S rRNA gene phylogenetic analysis. Serratia sp. was able to grow in a poor medium consisting of mineral salts and using methidathion as the sole carbon source at a concentrations of 50–150 mg/L. The effects of multifactors on degradation of methidathion in pure cultures by Serratia sp. were investigated using an orthogonal experimental design L₉ (3⁴). On the basis of range analysis and ANOVA results, the most significant factors were temperature and inoculum size. The optimal conditions for methidathion biodegradation in pure cultures were a temperature in 30 °C, an inoculum size of 10 %, pH?=?7 and an aeration rate of 200 rpm. Two different concentrations of strain SPL-2 fermenting liquids (OD₆₀₀?=?0.2 and OD₆₀₀?=?0.4) were prepared and applied to remove methidathion residues from agricultural products, and this process can be described by a first order rate model. In contrast to controls, the DT₅₀ of methidathion was shortened by 35.7 %, 8.2 % and by 62.3 %, 57.5 % on OD₆₀₀?=?0.2 and OD₆₀₀?=?0.4 treated haricot beans and peaches, respectively. These results suggest that the isolated bacterial strain may have potential for use in bioremediation of methidathion-contaminated crops.     

Degradation of a xenobiotic textile dye, Disperse Brown 118, by Brevibacillus laterosporus

The toxic textile dye, Disperse Brown 118, was degraded by Brevibacillus laterosporus. 96 % decolorization was achieved within 48 h at pH 7, 40 °C at 50 mg dye l^?1 accompanied by significant increases in the activities of veratryl alcohol oxidase, tyrosinase and NADH-DCIP reductase. HPTLC and FT-IR spectroscopy confirmed biodegradation after dye decolorization. As identified by GC–MS, biodegradation products of Disperse Brown 118 were N-carbamoyl-2-[(8-chloroquinazolin-4-yl)oxy] acetamide and N-carbamoyl-2-(quinazolin-4-yloxy)acetamide which were much less toxic than parent dye as evidenced by phytotoxicity tests.     

Optimization of triazo Acid Black 210 dye degradation by Providencia sp. SRS82 and elucidation of degradation pathway

The current work is aimed to evaluate the degradation of triazo textile dye Acid Black 210 (AB210) by Providencia sp. SRS82 that degrade 100 mg/L dye within 90 min under optimum conditions and was also found tolerant to as high as 2000 ppm of dye AB210. Optimum conditions for decolourization and degradation of AB210 with the isolate were viz. temperature 30 °C, pH 8, NaCl concentration 2.5% (w/v) and initial cell load of 8 × 10⁸ cells/mL under static condition. Induction of intracellular and extracellular lignin peroxidase, intracellular laccase and tyrosinase, azoreductase, and DCIP reductase indicated their contribution in the biodegradation of AB210. The products obtained from Providencia sp. SRS82 degradation was monitored through UV–Vis spectrophotometer and were characterized by FTIR, HPTLC, HPLC, GC/MS and LCMS. The proposed metabolic pathway for the biodegradation of AB210 is elucidated for the first time, which showed production of 4 molecules of benzene, one of naphthalene and 4-aminophenyl-N-(4-amino phenyl) benzene sulphonamide. Microbial toxicity and cytotoxicity studies revealed the comparatively less toxic nature of metabolites generated after degradation of AB210. Providencia sp. SRS82 was found competent to degrade actual effluent and diverse dyes that could be present in textile industry effluent showing usefulness of the organism for possible commercial application.     

Biodegradation of C.I. Acid Blue 92 by Nasturtium officinale: Study of Some Physiological Responses and Metabolic Fate of Dye

The present study was conducted to evaluate the potential of aquatic vascular plant, Nasturtium officinale, for degradation of C.I. Acid Blue 92 (AB92). The effect of operational parameters such as initial dye concentration, plant biomass, pH, and temperature on the efficiency of biological decolorization process was determined. The reusability of the plant in long term repetitive operations confirmed the biological degradation process. The by-products formed during biodegradation process were identified by GC-MS technique. The effects of the dye on several plant physiological responses such as photosynthetic pigments content and antioxidant enzymes activity were investigated. The content of chlorophyll and carotenoids was significantly reduced at 20 mg/L of the dye. The activities of superoxide dismutase and peroxidase were remarkably increased in the plant root verifying their importance in plant tolerance to the dye contamination.     

A Possible Role of Aspergillus niger Mitochondrial Cytochrome c in Malachite Green Reduction Under Calcium Chloride Stress

In previous work, decolorization of malachite green (MG) was studied in Aspergillus niger in the presence and absence of calcium chloride stress. Decolorization took place within 24 h, and a signal transduction process that initiated MG decolorization was suggested to be involved. In the present study, further investigation of the relationship between calcium chloride stress and enhanced MG biodegradation was conducted at the sub-cellular level. MG-NADH reductase activity, a key enzyme in MG decolorization, was produced as decolorization commenced, and enzyme activity increased threefold upon exposure to calcium chloride. Inhibitors of cytochrome p450, Ca²⁺ channel activity as well as activity of the signaling protein phosphoinositide 3-kinase were tested. All three activities were inhibited to different extents resulting in reduced MG decolorization. Spectral analysis of the mitochondrial fraction showed a heme signal at 405 nm and A₄₀₅/A₂₈₀ ratio that is characteristic of the porphoryin ring of cytochromes. There were no peaks detected for cytochromes a or b, but a shoulder appearing at 550 nm was observed, which suggested that cytochrome c is involved; the absorbance for cytochrome c doubled after calcium chloride stress supporting this idea. MG decolorization took place via a series of demethylation steps, and cytotoxicity analysis revealed a decrease in the toxicity associated with generation of leucomalachite green.     

Degradation of paracetamol by pure bacterial cultures and their microbial consortium

Three bacterial strains utilizing paracetamol as the sole carbon, nitrogen, and energy source were isolated from a paracetamol-degrading aerobic aggregate, and assigned to species of the genera Stenotrophomonas and Pseudomonas. The Stenotrophomonas species have not included any known paracetamol degraders until now. In batch cultures, the organisms f1, f2, and fg-2 could perform complete degradation of paracetamol at concentrations of 400, 2,500, and 2,000 mg/L or below, respectively. A combination of three microbial strains resulted in significantly improved degradation and mineralization of paracetamol. The co-culture was able to use paracetamol up to concentrations of 4,000 mg/L, and mineralized 87.1 % of the added paracetamol at the initial of 2,000 mg/L. Two key metabolites of the biodegradation pathway of paracetamol, 4-aminophenol, and hydroquinone were detected. Paracetamol was degraded predominantly via 4-aminophenol to hydroquinone with subsequent ring fission, suggesting new pathways for paracetamol-degrading bacteria. The degradation of paracetamol could thus be performed by the single isolates, but is stimulated by a synergistic interaction of the three-member consortium, suggesting a possible complementary interaction among the various isolates. The exact roles of each of the strains in the consortium need to be further elucidated.     

Biodegradation of Methyl Orange by alginate-immobilized Aeromonas sp. in a packed bed reactor: external mass transfer modeling

Azo dyes are recalcitrant and xenobiotic nature makes these compounds a challenging task for continuous biodegradation up to satisfactorily levels in large-scale. In the present report, the biodegradation efficiency of alginate immobilized indigenous Aeromonas sp. MNK1 on Methyl Orange (MO) in a packed bed reactor was explored. The experimental results were used to determine the external mass transfer model. Complete MO degradation and COD removal were observed at 0.20 cm bead size and 120 ml/h flow rate at 300 mg/l of initial dye concentration. The degradation of MO decreased with increasing bead sizes and flow rates, which may be attributed to the decrease in surface of the beads and higher flux of MO, respectively. The experimental rate constants (k _ps) for various beads sizes and flow rates were calculated and compared with theoretically obtained rate constants using external film diffusion models. From the experimental data, the external mass transfer effect was correlated with a model J _D = K Re ^?(1 ? n). The model was tested with K value (5.7) and the Colburn factor correlation model for 0.20, 0.40 and 0.60 bead sizes were J _D = 5.7 Re ^?0.15, J _D = 5.7 Re ^?0.36 and J _D = 5.7 Re ^?0.48, respectively. Based on the results, the Colburn factor correlation models were found to predict the experimental data accurately. The proposed model was constructive to design and direct industrial applications in packed bed reactors within acceptable limits.     

Performance of trichlorfon degradation by a novel <Emphasis Type="Italic">Bacillus tequilensis</Emphasis> strain PA F-3 and its proposed biodegradation pathway

The novel trichlorfon (TCF)-degrading bacterium PA F-3, identified as Bacillus tequilensis, was isolated from pesticide-polluted soils by using an effective screening and domesticating procedure. The TCF biodegradation pathways of PA F-3 were also systematically elucidated. As revealed by high-performance liquid chromatography, the TCF residues in the mineral salt medium demonstrated that PA F-3 can utilize TCF as its sole carbon source and reach the highest degradation of 71.1 % at an initial TCF concentration of 200 mg/L within 5 days. The TCF degradation conditions were optimized using response surface methodology as follows: temperature, 28 °C; inoculum amount, 4 %; and initial TCF concentration, 125 mg/L. Biodegradation treatments supplemented with exogenous carbon sources and yeast extract markedly increased the microbial dry weights and TCF-degrading performance of PA F-3, respectively. Meanwhile, five metabolic products of TCF were identified through gas chromatography/mass spectrometry, and a biodegradation pathway was proposed. Results indicated that deoxidation and dehydration (including the cleavage of the P–C phosphonate bond and the C–O bond) were the preferred metabolic reactions of TCF in this TCF-degrading bacterium.     

Biodegradation of reactive dye (Verofix Red) by the white-rot fungus Phanerochaete chrysosporium using Box-Behnken experimental design

Biodegradation of reactive dye using the white rot fungus Phanerochaete chrysosporium was demonstrated by the disappearance of the colour of reactive dye. An increase in dye concentration showed decreased dye degradation, and maximum dye degradation and increased biomass was observed in medium amended with limited source of nitrogen. Increasing days showed increased biomass production as well as dye degradation. Box- Behnken design with three variables like dye concentration (200, 700 and 1200?mg/l), days (2, 6 and 10) and nitrogen concentration at three different levels (0.054, 0.081 and 0.108?g/l) were studied to identify a significant correlation between the effect of these variables on the amount of biodegradation of reactive dye. The methodology identifies the principal experimental variables, which have the greatest effect in the biodegradation process. The experimental values are in good agreement with predicted values, the correlation coefficient being 0.9988.     

Aerobic decolorization of Acid Brilliant Scarlet GR by microbial community and the community dynamics during sequencing batch processes

In this research, aerobic decolorization of Acid Brilliant Scarlet GR by microbial community was studied. Effects of conditions and dye concentraion on decolorization processes were investigated. Additionally, continuous decolorization was evaluated through sequencing batch tests and the microbial dynamics during this process was analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis. The results showed that 100 mg l^?1 of the dye was completely decolorized within 12 h, which was mainly caused by biodegradation. The optimal decolorization conditions were as follows: inoculation size 2.07 g l^?1 (wet cell pellet), rotation speed 150 r min^?1, pH 5.0–7.0 and 30 °C. The processes were well described by zero-order kinetics, and more than 700 mg l^?1 of the dye would inhibit the activity of the consortium. Furthermore, the microbial community exhibited high efficiency in sequencing batch processes for continuous decolorization. Microbial community structure shifted obviously when exposed to higher concentration of the dye (500 mg l^?1), and all the dominant microorganisms were affiliated with four different phyla of Actinobacteria, Bacteroidetes, Proteobacteria and Firmicutes.     

Adsorption with biodegradation for decolorization of reactive black 5 by Funalia trogii 200800 on a fly ash-chitosan medium in a fluidized bed bioreactor-kinetic model and reactor performance

A non-steady-state mathematical model system for the kinetics of adsorption and biodegradation of reactive black 5 (RB5) by Funalia trogii (F. trogii) ATCC 200800 biofilm on fly ash-chitosan bead in the fluidized bed process was derived. The mechanisms in the model system included adsorption by fly ash-chitosan beads, biodegradation by F. trogii cells and mass transport diffusion. Batch kinetic tests were independently performed to determine surface diffusivity of RB5, adsorption parameters for RB5 and biokinetic parameters of F. trogii ATCC 200800. A column test was conducted using a continuous-flow fluidized bed reactor with a recycling pump to approximate a completely-mixed flow reactor for model verification. The experimental results indicated that F. trogii biofilm bioregenerated the fly ash-chitosan beads after attached F. trogii has grown significantly. The removal efficiency of RB5 was about 95 % when RB5 concentration in the effluent was approximately 0.34 mg/L at a steady-state condition. The concentration of suspended F. trogii cells reached up to about 1.74 mg/L while the thickness of attached F. trogii cells was estimated to be 80 μm at a steady-state condition by model prediction. The comparisons of experimental data and model prediction show that the model system for adsorption and biodegradation of RB5 can predict the experimental results well. The approaches of experiments and mathematical modeling in this study can be applied to design a full-scale fluidized bed process to treat reactive dye in textile wastewater.     

Pathway and Molecular Mechanisms for Malachite Green Biodegradation in Exiguobacterium sp. MG2

Malachite green (MG), N-methylated diaminotriphenylmethane, is one of the most common dyes in textile industry and has also been used as an effective antifungal agent. However, due to its negative impact on the environment and carcinogenic effects to mammalian cells, there is a significant interest in developing microbial agents to degrade this type of recalcitrant molecules. Here, an Exiguobacterium sp. MG2 was isolated from a river in Yunnan Province of China as one of the best malachite green degraders. This strain had a high decolorization capability even at the concentration of 2500 mg/l and maintained its stable activity within the pH range from 5.0 to 9.0. High-pressure liquid chromatography, liquid chromatography-mass spectrometry and gas chromatography–mass spectrometry were employed to detect the catabolic pathway of MG. Six intermediate products were identified and a potential biodegradation pathway was proposed. This pathway involves a series of reactions of N-demethylation, reduction, benzene ring-removal, and oxidation, which eventually converted N-methylated diaminotriphenylmethane into N, N-dimethylaniline that is the key precursor to MG. Furthermore, our molecular biology experiments suggested that both triphenylmethane reductase gene tmr and cytochrome P450 participated in MG degradation, consistent with their roles in the proposed pathway. Collectively, our investigation is the first report on a biodegradation pathway of triphenylmethane dye MG in bacteria.