Box-Behnken design in the development of optimized complex medium for phenol degradation using Pseudomonas putida (NICM 2174)

The biodegradation of phenol by Pseudomonas putida (NICM 2174), a potential biodegradent of phenol has been investigated for its degrading potential under different operating conditions. Box-Behnken design has been employed to study the effect of different experimental variables. Four variables of maltose (0.25, 0.5, 0.75?g/l), phosphate (3, 12.5, 22?g/l), pH (7, 8, 9) and temperature (30?°C, 32?°C, 34?°C) were used to identify the significant effects and interactions in the batch studies. A second order polynomial regression model, has been developed using the experimental data. It was found that the degrading potential of Pseudomonas putida (NICM 2174) was strongly affected by the variations in maltose, phosphate, pH and temperature. The experimental values were in good agreement with the predicted values, the correlation coefficient was found to be 0.9980. Optimum conditions of the variables for the growth of Pseudomonas putida (NICM2174) and for maximum biodegradation of phenol are maltose (0.052?g/l), phosphate (8.97?g/l), pH (7.9) and temperature (31.5?°C).     

Biodegradation of malachite green by Ochrobactrum sp.

This study presents the biodegradation of malachite green (MG), a triphenylmethane dye, using a novel microorganism isolated from textile effluent contaminated environment. The organism responsible for degradation was identified as Ochrobactrum sp JN214485 by 16S rRNA analysis. The effect of operating parameters such as temperature, pH, immobilized bead loading, and initial dye concentration on % degradation was studied, and their optimal values were found to be 30 °C, 6, 20 g/L and 100 mg/L, respectively. The analysis showed that the extracellular enzymes were responsible for the degradation. The biodegradation of MG was confirmed by UV–visible spectroscopic and FTIR analysis. The phytotoxicity test concluded that the degradation products were less toxic compared to MG. The kinetics of biodegradation was studied and the activation energy was found to be 10.65 kcal/mol.     

Toluene biodegradation and biofilm growth in an aerobic fixed-film reactor

Summary Aerobic biodegradation of toluene in a biofilm system was investigated. Toluene is easily biodegradable, like several other aromatic compounds. The degradation was first order at bulk concentrations lower than 0.14 mg/l and zero order above 6–8 mg/l. An average yield coefficient of 1 mg biomass/mg toluene degraded was found. A chemical oxygen demand balance relative to three biofilm growth scenarios showed that only a minor fraction of the carbon in the influent accumulated as biomass in the reactor. Of this accumulated biomass only a small fraction was active biomass, about 5% protein. A characterization of the carbon fractions leaving the reactor showed a significant production of soluble polymers and formation of suspended biomass. The latter was probably due to the detachment of filamentous bacteria. A decrease in toluene degradation was observed when the oxygen concentration was increased from 5 to about 20 mg/l. Future studies must show if this effect was due to inhibition. Correspondence to: J. P. Arcangeli     

活性X-3B红染料对作物生态毒理指标影响的比较研究

采用作物种子暴露实验 ,研究了小麦、白菜和水稻等 3种不同作物对活性X 3B红染料污染暴露的生态毒理学指标 .结果表明 ,小麦、白菜和水稻对活性X 3B红染料污染暴露的反应各异 ,具体表现为对3种作物的种子发芽抑制半效应浓度分别为 896 5、70 10和 75 14mg·L-1,对根伸长抑制的半效应浓度分别为 6 5 34、5 882和 45 70mg·L-1;这 3种作物在从种子萌发起至第 7天时去残余种子或种皮后的鲜生物量、干生物量均随活性X 3B红暴露浓度的增加而降低 ,但鲜生物量的降低率普遍高于干生物量的降低率 ;当作物种子暴露于高浓度 (4 5 0 0和 5 0 0 0mg·L-1)的活性X 3B红时 ,小麦生物量受该有机染料污染暴露的影响最为敏感 ,水稻其次 ,白菜最为迟钝 ;就小麦、白菜和水稻等 3种作物对活性X 3B红染料污染暴露的抗性而言 ,小麦最强 ,白菜次之 ,水稻最弱 .     

Use of Box-Behnken design of experiments for the adsorption of verofix red using biopolymer

Box-Behnken design with three variables like temperature, pH?and particle size at three different levels was studied to identify a significant correlation between the effect of these variables to the amount of dye adsorbed. The methodology identifies the principal experimental variables, which have the greatest effect on the adsorption process. The experimental values are in good agreement with predicted values, the correlation coefficient was found to 0.9250.     

Kinetic behaviour of waste tyre rubber as microorganism support in an anaerobic digester treating cane molasses distillery slops

The kinetics of anaerobic digestion of cane molasses distillery slops was investigated using a continuous-flow bioreactor which contained waste tyre rubber as support, to which the microorganisms became immobilized. Hydraulic retention times (HRT) ranging from 1 to 10 days were investigated at an average influent chemical oxygen demand (COD) concentration of 47.7?g/l. The maximum substrate utilization rate, k, and half saturation coefficient, K _L, were determined to be 1.82?kg COD_removed/kg VSS day and 0.33?kg COD/kg VSS day. The yield coefficient, Y, and sludge decay rate coefficient, K _d, were also determined to be 0.06?kg VSS/kg COD_removed and 0.05?day^-1, respectively. Methane production was maximum (6.75?l/l day) at a 2 day HRT corresponding to a biomass loading rate of 2.578?kg COD/kg VSS day. Biogas yield ranged between 0.51?l/g COD (HRT=2 days) and 0.25?l/g COD (HRT=1?day). In addition, the methane percentage in the biogas varied between 70.5% (HRT=10?days) and 47.5% (HRT=1?day). The close relationship between biomass loading rate and specific substrate utilization rate supported the use of Monod equations. Finally, the experimental values of effluent substrate concentration were reproduced with deviations equal to or less than 10% in every case.     

Kinetics of phenol degradation using Pseudomonas putida MTCC 1194

Pseudomonas putida (MTCC 1194) has been used to degrade phenol in water in the concentration range 100–1000?ppm. The inhibition effects of phenol as substrate have become predominant above the concentration of 500?ppm (5.31?mmoles/dm³). The optimum temperature and initial pH required for maximum phenol biodegradation were 30?°C and 7.00 respectively. From the degradation data the activation energy (E _a ) was found to be equal to 13.8?kcal/g mole substrate reacted. The most suitable inoculum age and volume for highest phenol degradation were 12?hrs and 7% v/v respectively. Surfactants had negligible effect on phenol biodegradation process for this microorganism. Monod model has been used to interpret the free cell data on phenol biodegradation. The kinetic parameters have been estimated upto initial concentration of 5.31?mmoles/dm³. μ _max and K _S gradually increased with higher concentration of phenol. However, beyond the phenol concentration of 5.31?mmoles/dm³, the inhibition became prominant. The μ _max has been to be a strong function of initial phenol concentration. The simulated and the experimental phenol degradation profiles have good correspondence with each other.     

Thermal decomposition kinetics of wheat straw treated by Phanerochaete chrysosporium

Combining biological pretreatment with thermal processing may offer an alternative strategy for efficient conversion of lignocellulosic biomass into fuels and chemicals. The thermal decomposition kinetics of biologically pretreated wheat straw by Phanerochaete chrysosporium was investigated in this study using thermogravimetry (TG) - deconvoluted thermogravimetry (DTG) techniques and the Friedman method. This study revealed that biological pretreatment reduced the thermal degradation temperature of the biomass significantly. Relying on the thermal behavior of the biologically pretreated wheat straw, we proposed two biomass degradation phases during the biological degradation of wheat straw. The first phase of biodegradation (within 10 days of biological pretreatment) improved the efficiency of pyrolysis by reducing the temperature demand. In the second phase (after 10 days), although the efficiency of pyrolysis displayed the similar trend as the first phase, it showed a significant increase in activation energy demand. This process is greatly influenced by the residual lignin and cellulose ratios in the biomass. These experimental results will be useful in developing a biological pretreatment based thermochemical conversion process for lignocellulosic biomass.     

Photocatalytic decolorization of congo red over ZnO powder using Box–Behnken design of experiments

Photocatalytic decolorization of congo red under sunlight illumination has been examined using ZnO catalyst. Batch experiments were conducted and Box-Behnken design has been employed to study the effect of different variables on the photodecolorization. Four variables such as dye concentration (0.05, 0.075, 0.10 g/l), weight of catalyst ZnO (0.025, 0.14, 0.25 g/l), pH (4, 7, 10) and time (1, 2, 3 (h)) were used to identify the significant effects and interactions in the batch studies. A second order polynomial regression model has been developed using the experimental data. It was found that the photodecolorization potential of ZnO was strongly affected by the variations in dye concentration, weight of catalyst ZnO, pH and time. The experimental values were in good agreement with the predicted values and the correlation coefficient was found to be 0.9982. Optimum conditions of the variables for the maximum photodecolorization are dye concentration (0.05 g/l) ZnO (0.16 g/l), pH (7.0) and time (2.0) (h). The maximum percentage of photodecolorization was observed to be 97%.     

Microbial decolorization and degradation of synthetic dyes: a review

The synthesis of dyes and pigments used in textiles and other industries generate the hazardous wastes. A dye is used to impart color to materials of which it becomes an integral part. The waste generated during the process and operation of the dyes commonly found to contain the inorganic and organic contaminant leading to the hazard to ecosystem and biodiversity causing impact on the environment. The amount of azo dyes concentration present in wastewater varied from lower to higher concentration that lead to color dye effluent causing toxicity to biological ecosystem. The physico-chemical treatment does not remove the color and dye compound concentration. The decolorization of the dye takes place either by adsorption on the microbial biomass or biodegradation by the cells. Bioremediation takes place by anaerobic and/or aerobic process. The anaerobic process converts dye in toxic amino compounds which on further treatment with aerobic reaction convert the intermediate into CO₂ biomass and inorganics. In the present review the decolorization and degradation of azo dyes by fungi, algae, yeast and bacteria have been cited along with the anaerobic to aerobic treatment processes. The factors affecting decolorization and biodegradation of azo dye compounds such as pH, temperature, dye concentration, effects of CO₂ and Nitrogen, agitation, effect of dye structure, electron donor and enzymes involved in microbial decolorization of azo dyes have been discussed. This paper will have the application for the decolorization and degradation of azo dye compound into environmental friendly compounds.     

Design of experiments in the biodegradation of phenol using immobilized Pseudomonas pictorum (NICM-2077) on activated carbon

Pseudomonas pictorum (NICM-2077) immobilized on various matrices are used to protect the microbes from confronting shock loads of concentrated phenol. The cells were immobilized in activated carbon and were used in biodegradation of phenol. Biodegradation of phenol using immobilized Activated Carbon matrix played an important role in reducing the toxicity of phenol. The degradation was carried and using the Box-Behnken model and analysis of variance have been applied to the experimental degradation studies. Response surface method with three levels of phenol concentration (0.200, 0.400, 0.600 g/l), activated carbon (0.5, 1.0, 1.5 g/l) and pH (7, 8, 9) were used in the identification of significant effects and interactions in the biodegradation studies. Phenol removal rate increases especially when the degradation medium was supplemented with utilizable carbon sources. A first-order polynomial regression model, which was used at first for analysis of the experiment had a significant lack of fit. Therefore, linear and quadratic terms were incorporated into the regression model through variable selection procedures. Effect of incubation phenol concentration, activated carbon and pH were significant. The predicted values using Box-Behnken model was found to be in close agreement with the experimental values, as indicated by the correlation coefficient values of 0.9463.     

Anaerobic biodegradation of a petrochemical waste-water using biomass support particles

During the anaerobic biodegradation of effluent from a dimethyl terephthalate (DMT) manufacturing plant, reduction in chemical oxygen demand (COD) degradation and biogas formation was observed after the waste-water concentration exceeded 25% of added feed COD. This condition reverted back to normal after 25–30 days when the DMT waste-water concentration in the feed was brought down to a non-toxic level. However, the above effects were observed only after the concentration of DMT waste-water reached more than 75% of added feed COD when biomass support particles (BSP) were augmented to the system. In the BSP system, a biomass concentration of up to 7000 mg/l was retained and the sludge retention time increased to > 200 days compared to 2200 mg/l and 8–10 days, respectively, in the system without BSP (control). Formaldehyde in the waste-water was found to be responsible for the observed toxicity. The BSP system was found to resist formaldehyde toxicity of up to 375 mg/l as against 125 mg/l in the control system. Moreover, the BSP system recovered from the toxicity much faster (15 days) than the control (25–30 days). The advantages of the BSP system in anaerobic treatment of DMT waste-water are discussed. Correspondence to: C. Ramakrishna     

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.     

Allelopathic effect of aqueous extracts of three weed species on the growth and leaf chlorophyll content of bread wheat

The purpose of this study was to evaluate the allelopathic effect of weeds (Avena fatua, Melilotus officinalis and Polypogon hissaricus) on germination, growth, dry biomass and chlorophyll concentration of three cultivars of wheat (Ata Habib, Pirsabaq and Serin). In germination test, different concentrations of aqueous extracts (5, 10 and 15?g/l) of the three weeds significantly reduced percent germination; however, 15?g/l extract of M. officinalis resulted in complete failure of germination of cultivar Pirsabaq. In pot culture, root and shoot length, chlorophyll concentration and seedling dry biomass of the three wheat varieties showed differential responses to different weeds. Aqueous extract at 15?g/l of A. fatua increased root and shoot length and dry biomass of cultivar Pirsabaq; however, these parameters were significantly retarded in other two wheat cultivars by extract of weeds. Moisture content of the cultivars did not show any response to allelopathic stress of the weeds. In contrast, chlorophyll concentration in Pirsabaq and Serin was significantly increased by aqueous extract of all the weeds but reduced it in cultivar Ata Habib by 50%. In general, Ata Habib was found to be the most sensitive cultivar to the imposed allelopathic stress. The phytotoxic potential of three weeds was found in the order of A. fatua?>?M. officinalis?>?P. hissaricus.     

Biodegradation of bioaccessible textile azo dyes by Phanerochaete chrysosporium

Azo dyes are important chemical pollutants of industrial origin. Textile azo dyes with bioaccessible groups for lignin degrading fungi, such as 2-methoxyphenol (guaiacol) and 2,6-dimethoxyphenol (syringol), were synthesised using different aminobenzoic and aminosulphonic acids as diazo components. The inocula of the best biodegradation assays were obtained from a pre-growth medium (PAM), containing one of the synthesised dyes. The results of the dye biodegradation assays were evaluated every 7 days, by the decrease of the absorbance at the maximum wavelength of the dye, by the decrease of the sucrose concentration in the culture medium and by the increase of the biomass during the 28 days of assay. It was observed that the extent of dye biodegradation depended on the sucrose concentration, on the degraded dye structure and, on the dye present in the PAM medium.     

Biodegradation of bioaccessible textile azo dyes by Phanerochaete chrysosporium

Azo dyes are important chemical pollutants of industrial origin. Textile azo dyes with bioaccessible groups for lignin degrading fungi, such as 2-methoxyphenol (guaiacol) and 2,6-dimethoxyphenol (syringol), were synthesised using different aminobenzoic and aminosulphonic acids as diazo components. The inocula of the best biodegradation assays were obtained from a pre-growth medium (PAM), containing one of the synthesised dyes. The results of the dye biodegradation assays were evaluated every 7 days, by the decrease of the absorbance at the maximum wavelength of the dye, by the decrease of the sucrose concentration in the culture medium and by the increase of the biomass during the 28 days of assay. It was observed that the extent of dye biodegradation depended on the sucrose concentration, on the degraded dye structure and, on the dye present in the PAM medium.     

Optimization of a medium for enhancing nicotine biodegradation by Ochrobactrum intermedium DN2

AIMS: To optimize a medium for nicotine degradation by Ochrobactrum intermedium DN2 in presence of yeast extract, glucose and Tween 80 using response surface methodology (RSM). METHODS AND RESULTS: In this study, the effects of yeast extract, glucose and Tween 80 on nicotine degradation were investigated in flasks using a novel nicotine-degrading bacterium, O. intermedium DN2. A full factorial central composite design was applied in the design of experiments and in the analysis of the experimental data. The results showed that the most significant variable influencing nicotine degradation was yeast extract, followed by glucose, and then Tween 80. Moreover these three factors interacted with each other and combined to produce positive effects on nicotine degradation. The experimental data also allowed the development of an empirical model (P < 0.0001) describing the inter-relationship between independent and dependent variables. By solving the regression equation, the optimal values of the variables were determined as: yeast extracts 0.094%, glucose 0.101% and Tween 80 0.080%. Using the medium obtained, about 1,220 mg l(-1) of nicotine was degraded (95.55%) within 10 h at the specific biodegradation of 116.59 mg l(-1) h(-1) in 30-l bioreactor containing 25-l tobacco extract. CONCLUSIONS: An optimal medium of nicotine degradation by the strain DN2 was obtained. SIGNIFICANCE AND IMPACT OF THE STUDY: RSM proved to be reliable in developing the model, optimizing factors and analysing interaction effects. The results provide better understanding on the interactions between yeast extract, glucose and Tween 80 for nicotine biodegradation.     

Improved biodegradation of Congored by using Bacillus sp

The biodegradation of Congored, a toxic azo dye, was studied by using a hybrid technique involving sonolysis as pretreatment followed by biological treatment. The experiments were carried out with and without pretreatment using dye solution as a sole source of nutrition with an isolated and acclimatized strain of Bacillus sp. obtained from tannery industry effluent. The pretreatment time was varied as 30, 60, 90, 120, 150 and 180 min and then the pretreated dye solution was subjected to biological treatment. The effectiveness of pretreatment was compared with the results of biological degradation of non pretreated Congored and the results showed that the pretreatment improved the efficiency of the biodegradation of Congored. During the biological degradation, the increase in initial dye concentration decreased the decolorization rate and at high concentrations (1500 and 2000 mg/l), the inhibition was observed. The optimum pH and temperature were determined to be 7.0 and 37 degrees C, respectively. The data obtained through biodegradation experiments were fitted with five different kinetic models and the results were analyzed.     

Biological decolorization of xanthene dyes by anaerobic granular biomass

Biodegradation of a xanthene dyes was investigated for the first time using anaerobic granular sludge. On a first screening, biomass was able to decolorize, at different extents, six azo dye solutions: acid orange 7, direct black 19, direct blue 71, mordant yellow 10, reactive red 2 and reactive red 120 and two xanthene dyes--Erythrosine B and Eosin Y. Biomass concentration, type of electron donor, induction of biomass with dye and mediation with activated carbon (AC) were variables studied for Erythrosine B (Ery) as model dye. Maximum color removal efficiency was achieved with 4.71 g VSS L?1, while the process rates were independent of the biomass concentration above 1.89 g VSS L?1. No considerable effects were observed when different substrates were used as electron donors (VFA, glucose or lactose). Addition of Ery in the incubation period of biomass led to a fivefold increase of the decolorization rate. The rate of Ery decolorization almost duplicated in the presence of commercial AC (0.1 g L?1 AC?). Using different modified AC samples (from the treatment of AC?), a threefold higher rate was obtained with the most basic one, AC(H?), as compared with non-mediated reaction. Higher rates were obtained at pH 6.0. Chemical reduction using Na?S confirmed the recalcitrant nature of this dye. The results attest that decolorization of Ery is essentially due to enzymatic and adsorption phenomena.     

Reactive red azo dye degradation in a UASB bioreactor: Mechanism and kinetics

Textile industry uses azo dyes in its processes, which are complex organic molecules that are not easy to be degraded. Reactive dyes are especially difficult to remove from wastewater because of the characteristics of the molecule: one or more azo bonds, naphthalene‐disulfonate, triazine or chloro‐triazine, and phenyl‐amine groups. The degradation of the azo dye reactive red 272 was studied under anaerobic conditions in a hybrid Upflow Anaerobic Sludge Bed reactor (UASB) with an activated carbon bed. An adapted consortium of microorganisms was used in the kinetic study (batch) and to inoculate the UASB reactor. The experimental design identified the main factors determining the dye reduction efficiency are the initial concentration of dye and dextrose (as electron donor) and the residence time in the reactor. Dye reduction rate was decreased as the concentration increases in the wastewater; as a result, a kinetic model with a change from first to second order is proposed. The kinetic study showed that the process is first abiotic (adsorption) and then biotic (biodegradation).