Substrate Versatility Studies on the Aerobic Degradation of BTX Compounds
01 Jan 2005-pp 105-121
TL;DR: In this article, the versatility of a bacterial consortium taken from a domestic sewage treatment plant was evaluated using a mixture of benzene, Toluene and Xylene (BTX) as the sole carbon source.
Abstract: Biodegradation studies were carried out in aerobic batch systems using Benzene, Toluene and Xylene (BTX) as the sole carbon source to evaluate the versatility of a bacterial consortium taken from a domestic sewage treatment plant. This mixed microbial culture was acclimatized using individual BTX compounds and the potential capability of microbes precultured on a single substrate to degrade other compounds was studied over a wide range of BTX concentrations (∼50-500mg/L). The biodegradation pattern and growth rates ascertained experimentally in these versatility studies were compared with results obtained from individual degradation experiments studied earlier. Similar growth pattern was observed for all the substrate with inhibition occurring at higher concentrations (∼200 mg/L for Benzene and Xylene, ∼250mg/L for Toluene). Toluene was degraded more than the other substrates followed by benzene and xylene. Adaptation to a more toxic compound like benzene and xylene improved the utilization of toluene. On the other hand microbes grown on a less toxic compound (toluene), grew at a lower rate in the presence of more toxic compounds. Kinetic parameters such as μmax, KI and KS were determined using the Haldane’s and Levenspiel’s substrate inhibition models. Results from Haldane’s model were more illustrative of the experimental observations and were found to satisfactorily explain the system behavior.
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TL;DR: The results showed that, increasing the concentration of xylene increased the cumulative BTEX removal (BTEXT-RE), however the reverse occurred when benzene concentrations were increased from low to high levels, and the RSM approach was found efficient in explaining the main, squared and interaction effects among individual BTEX concentrations on the BTEXT- RE in a more statistically meaningful way.
Abstract: The removal of benzene, toluene, ethylbenzene and xylene (BTEX) as quaternary mixtures were studied in batch systems using a well-defined mixed microbial culture. The synergistic and antagonistic effects of total BTEX removal (BTEXT-RE) due to the presence of mixed substrate was evaluated through experiments designed by response surface methodology (RSM). The low and high concentrations of individual BTEX were 15 and 75 mg l(-1), respectively. The results showed that, increasing the concentration of xylene increased the cumulative BTEX removal (BTEXT-RE), however the reverse occurred when benzene concentrations were increased from low to high levels. A mixed response of increasing and decreasing trend in the BTEXT-RE value was observed when either of toluene or ethylbenzene concentration was increased. When the concentrations of individual BTEX compounds were 30 mg l(-1), the BTEXT-RE was about 58%. Complete BTEXT-RE was achieved at optimal BTEX concentrations of 48.1, 45.6, 49.3 and 56.6 mg l(-1). The RSM approach was found efficient in explaining the main, squared and interaction effects among individual BTEX concentrations on the BTEXT-RE in a more statistically meaningful way.
65 citations
01 Jan 1994
TL;DR: In this article, a new internal filter feedback system with a stainless steel filter was introduced and its application for continuous ethanol fermentation was investigated and its performance was highly influenced by agitation speed and yeast concentration.
Abstract: A new internal filter feedback system with a stainless steel filter was introduced and its application for continuous ethanol fermentation was investigated. The filter performance was highly influenced by agitation speed and yeast concentration. Retention coefficient with a filter of 2 μm pore size was found more than 97.5%, and the filter was suitable for yeast separation. Maximum yeast concentration was 157 g/L and the best operable cell concentration was between 90 and 150 g/L. Which was similar to that obtained in the external membrane cell recycle culture. The cell concentration in the fermentor was maintained by manipulation of dilution rate and bleed ratio with the growth rate. The internal filter feedback system was successfully operated for more than 10 days. This study shows that the internal filter feedback system with a stainless steel filter can be used high‐density cell culture and ethanol fermentation. Furthermore, it can be scaled up more easily than the external cell recycle system. © 1993 John Wiley & Sons, Inc.
39 citations
TL;DR: Fitting the experimental data to pseudo first-order biodegradation kinetics model showed the BX were biodegraded faster in the presence of optimum surfactant at pH 7 than pH 4, demonstrating that acclimating wastewater inoculum at pH 4 increased the fungal to bacterial ratio.
Abstract: The aim of this work was to explore the effect of lowering pH and application of surfactants (Brij 35, Tween 20 and Saponin) in increasing bioavailability and biodegradability of benzene and o-xylene (BX) as two hydrophobic VOCs in a liquid mixture. All experiments were conducted at neutral and acidic pH to evaluate the effect of population change from bacteria to fungi on the BX biodegradation. The experiments demonstrated that acclimating wastewater inoculum at pH 4 increased the fungal to bacterial ratio. An increase of 11% for benzene and 22% for o-xylene was observed at pH 4 unamended-culture as compared to pH 7. Brij 35 was chosen as the optimum surfactant which was favorable for enhancing the bioavailability of BX at pH 4. Fitting the experimental data to pseudo first-order biodegradation kinetics model showed the BX were biodegraded faster in the presence of optimum surfactant at pH 7 than pH 4.
10 citations
TL;DR: The results showed that P. aeruginosa S8 strain has a high o-cresol biodegradation potential; it could degrade completely 1250 mg L−1 o- cresol within 85 h and was slightly affected by alkalinity, presence of heavy metals and salinity.
Abstract: The aim of this study was to evaluate the potential of a selected Pseudomonas aeruginosa strain (strain S8) isolated from an Algerian soil to degrade o-cresol in water. This strain was used to study the biodegradation of o-cresol in batch aerobic experiments under variable pH values, heavy metals ions (Zn2+, Cd2+ and Cu2+) and NaCl concentrations. The results showed that P. aeruginosa S8 strain has a high o-cresol biodegradation potential; it could degrade completely 1250 mg L−1 o-cresol within 85 h. Furthermore, o-cresol biodegradation potential of the strain was slightly affected by alkalinity (pH 9), presence of heavy metals and salinity (NaCl). Growth kinetics and degradation activity data obtained for the concentrations ranging between 250–1250 mg L−1 fitted well to Andrews growth kinetic model with a coefficient of determination (R2) higher than 0.99. Due to its high o-cresol biodegradation potential and its relative tolerance to alkalinity, salinity and heavy metals, the strain S8 seems to ...
4 citations
References
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Book•
01 Jan 1993
TL;DR: An Introduction to Environmental Organic Chemicals is given in this article, where the authors present an overview of the main steps in the development of these processes, including the following: Sorption I: General Introduction and Sorption Processes Involving Organic Matter. Sorption II: Partitioning to Living Media - Bioaccumulation and Baseline Toxicity.
Abstract: Preface. Part I: Introduction. 1. General Topic and Overview. 2. An Introduction to Environmental Organic Chemicals. Part II: Equilibrium Partitioning Between Gaseous, Liquid, and Solid Phases. 3. Partitioning: Molecular Interactions and Thermodynamics. 4. Vapor Pressure. 5. Activity Coefficient and Solubility in Water. 6. Air-Organic Solvent and Air-Water Partitioning. 7. Organic Liquid-Water Partitioning. 8. Organic Acids and Bases: Acidity Constant and Partitioning Behavior. 9. Sorption I: General Introduction and Sorption Processes Involving Organic Matter. 10. Sorption II: Partitioning to Living Media - Bioaccumulation and Baseline Toxicity. 11. Sorption III: Sorption Processes Involving Inorganic Surfaces. Part III: Transformation Processes. 12. Thermodynamics and Kinetics of Transformation Reactions. 13. Chemical Transformations I: Hydrolysis and Reactions Involving Other Nucleophilic Species. 14. Chemical Transformations II: Redox Reactions. 15. Direct Photolysis. 16. Indirect Photolysis: Reactions with Photooxidants in Natural Waters and in the Atmosphere. 17. Biological Transformations. Part IV: Modeling Tools: Transport and Reaction. 18. Transport by Random Motion. 19. Transport Through Boundaries. 20. Air-Water Exchange. 21. Box Models. 22. Models in Space and Time. Part V: Environmental Systems and Case Studies. 23. Ponds, Lakes, and Oceans. 24. Rivers. 25. Groundwater. Appendix. Bibliography. Index (Subject Index, Compound Index, List of Illustrative Examples).
4,403 citations
Book•
01 Jan 1961
TL;DR: In this paper, the biological processes that take place in the soil and their importance to soil fertility, plant growth, and environmental quality are investigated from both descriptive and functional viewpoints, including microbial ecology, the carbon and nitrogen cycles, mineral transformation, and ecological interrelationships.
Abstract: Characterizes soil microflora from descriptive and functional viewpoints; considers the biological processes that take place in the soil and their importance to soil fertility, plant growth, and environmental quality. Deals with the biochemical basis for soil processes, including microbial ecology, the carbon and nitrogen cycles, mineral transformation, and ecological interrelationships.
2,728 citations
TL;DR: The biodegradation of benzene, certain arenes, biphenyl and selected fused aromatic hydrocarbons, by single bacterial isolates, are dealt with in detail.
Abstract: Aromatic compounds of both natural and man-made sources abound in the environment. The degradation of such chemicals is mainly accomplished by microorganisms. This review provides key background information but centres on recent developments in the bacterial degradation of selected man-made aromatic compounds. An aromatic compound can only be considered to be biodegraded if the ring undergoes cleavage, and this is taken as the major criteria for inclusion in this review (although the exact nature of the enzymic ring-cleavage has not been confirmed in all cases discussed).
801 citations
"Substrate Versatility Studies on th..." refers background in this paper
...These compounds have been found to be degraded effectively by naturally occurring soil microorganisms, and other mixed aerobic bacterial populations (Smith, 1990; Alvarez and Vogel, 1991; Chang et al., 1993; Oh et al., 1994)....
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TL;DR: It is concluded that much of the diversity in shapes of mineralization curves is a result of the interactions of substrate concentration and population density.
Abstract: The rates of mineralization of [14C]benzoate by an induced population of Pseudomonas sp. were measured at initial substrate concentrations ranging from 10 ng/ml to 100 micrograms/ml. Plots of the radioactivity remaining in the culture were fit by nonlinear regression to six kinetic models derived from the Monod equation. These models incorporate only the variables of substrate concentration and cell density. Plots of the mineralization kinetics in cultures containing low, intermediate, and high initial substrate concentrations were well fit by first-order, integrated Monod, and logarithmic kinetics, respectively. Parameters such as maximum specific growth rate, half-saturation constant, and initial population density divided by yield agreed between cultures to within a factor of 3.4. Benzoate mineralization by microorganisms in acclimated sewage was shown to fit logistic (sigmoidal), Monod, and logarithmic kinetics when the compound was added at initial concentrations of 0.1, 1.0, and 10 micrograms/ml, respectively. The mineralization of 10 micrograms of benzoate per ml in sewage also followed logarithmic kinetics in the absence of protozoa. It is concluded that much of the diversity in shapes of mineralization curves is a result of the interactions of substrate concentration and population density. Nonlinear regression with models incorporating these variables is a valuable means for analysis of microbial mineralization kinetics.
405 citations
"Substrate Versatility Studies on th..." refers methods in this paper
...To develop more predictive capability of kinetic parameters, the rate data observed experimentally has to be fitted to appropriate kinetic models (Simkins and Alexander, 1984)....
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TL;DR: Of the models tested, a sum kinetics with interaction parameters (SKIP) model provided the best description of the paired substrate results, and provided an excellent prediction of the biodegradation kinetics for the three-component mixture.
Abstract: Although microbial growth on substrate mixtures is commonly encountered in bioremediation, wastewater treatment, and fermentation, mathematical modeling of mixed substrate kinetics has been limited. We report the kinetics of Pseudomonas putida F1 growing on benzene, toluene, phenol, and their mixtures, and compare mathematical models to describe these results. The three aromatics are each able to act as carbon and energy sources for this strain. Biodegradation rates were measured in batch cultivations following a protocol that eliminated mass transfer limitations for the volatile substrates and considered the culture history of the inoculum and the initial substrate to inoculum mass ratio. Toluene and benzene were better growth substrates than phenol, resulting in faster growth and higher yield coefficients. In the concentration ranges tested, toluene and benzene biodegradation kinetics were well described by the Monod model. The Monod model was also used to characterize phenol biodegradation by P. putida F1, although a small degree of substrate inhibition was noted. In mixture experiments, the rate of consumption of one substrate was found to be affected by the presence of the others, although the degree of influence varied widely. The substrates are catabolized by the same enzymatic pathway, but purely competitive enzyme kinetics did not capture the substrate interactions well. Toluene significantly inhibited the biodegradation rate of both of the other substrates, and benzene slowed the consumption of phenol (but not of toluene). Phenol had little effect on the biodegradation of either toluene or benzene. Of the models tested, a sum kinetics with interaction parameters (SKIP) model provided the best description of the paired substrate results. This model, with parameters determined from one- and two-substrate experiments, provided an excellent prediction of the biodegradation kinetics for the three-component mixture.
379 citations
"Substrate Versatility Studies on th..." refers background in this paper
...Values of indicate the ability of microbes to grow at low substrate levels (Reardon et al., 2000) and values indicate the sensitivity of the culture to substrate inhibition (Shim and Yang, 1999)....
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