Kinetics of phenol biodegradation in the presence of glucose

Mathematical modeling for operative improvement of the decoloration of Acid Red 27 by a novel microbial consortium of Trametes versicolor and Pseudomonas putida: A multivariate sensitivity analysis

In this work, it is presented a first approach of a mathematical and kinetic analysis for improving the decoloration and further degradation process of an azo dye named acid red 27 (AR27), by means of a novel microbial consortium formed by the fungus Trametes versicolor and the bacterium Pseudomonas putida. A multivariate analysis was carried out by simulating scenarios with different operating conditions and developing a specific mathematical model based on kinetic equations describing all stages of the biological process, from microbial growth and substrate consuming to decoloration and degradation of intermediate compounds. Additionally, a sensitivity analysis was performed by using a factorial design and the Response Surface Method (RSM), for determining individual and interactive effects of variables like, initial glucose concentration, initial dye concentration and the moment in time for bacterial inoculation, on response variables assessed in terms of the minimum time for: full decoloration of AR27 (R1 = 2.375 days); maximum production of aromatic metabolites (R2 = 1.575 days); and full depletion of aromatic metabolites (R3 = 12.9 days). Using RSM the following conditions improved the biological process, being: an initial glucose concentration of 20 g l-1, an initial AR27 concentration of 0.2 g l-1 and an inoculation moment in time of P. putida at day 1. The mathematical model is a feasible tool for describing AR27 decoloration and its further degradation by the microbial consortium of T. versicolor and P. putida, this model will also work as a mathematical basis for designing novel bio-reaction systems than can operate with the same principle of the described consortium.

Biodegradation modeling of phenol using Curtobacterium flaccumfaciens as plant-growth-promoting bacteria

Phenol is a major worry pollutant resulting from industrialized manufacturing and chemical reactions. The growth kinetics and biodegradation of phenol were initially investigated using C. flaccumfaciens, a recently identified plant growth stimulating bacterium. Based on the Haldane inhibition model, Haldane's growth kinetics inhibition coefficient (Ki), half-saturation coefficient (Ks), and the maximum specific growth rate (max) for phenol-dependent growth kinetics were estimated to be 329 (mg/L), 9.14 (mg/L), and 1.05 (h⁻¹), respectively. With a sum of squared error (SSR) of 1.36 × 10⁻³, the Haldane equation is well adapted to empirical data. The improved Gombertz model also accurately predicts phenol biodegradation trends. The rate of phenol biodegradation and the lag time both increased as the initial phenol concentrations were increased. C. flaccumfaciens growth and phenol biodegradation were best achieved at a pH of 7.0 at a temperature of 28 °C incubation. A phenol biodegradation mechanism by C. flaccumfaciens has been proposed. In conclusion, this study revealed the ability of C. flaccumfaciens to promote plant growth and biodegrade phenol simultaneously. This could aid in rhizoremediation and crop yield preservation in phenol-stressed conditions.

Efficacy of free and encapsulated Bacillus lichenformis strain SL10 on degradation of phenol: A comparative study of degradation kinetics

The present study exemplifies phenol degradation efficacy of the free and encapsulated bacterial isolate, explored the degradation kinetics and storage stability in detail. In brief, isolation, identification and phenol degradation potential of the bacterial made from wastewater treated sludge samples. The organism identified as B. licheniformis demonstrates phenol degradation at a concentration more than 1500 ppm. Optimization of environmental parameters reduces the time taken for degradation considerably. The organism has further been encapsulated using whey protein and the efficacy of encapsulated species suggested that encapsulation protects the cells from high concentration of phenol and at the same time expedite the degradation of the chosen pollutant at appreciable level. The encapsulated species effectively degrade 3000 ppm concentration of phenol within 96 h of incubation. Both pH and temperature stability observed in the encapsulated species suggests the effectiveness of the encapsulation. The encapsulated cells displayed storage stability for a four week period at 4 C and reusability up to three exposures. Degradation effected through intracellular catechol 2,3 dioxygenase. In conclusion, encapsulation of B. licheniformis (i) protects the cells from direct exposure to toxic pollutants; (ii) facilitates the field scale application and (iii) eliminate the practical difficulties in handling wet biomass in field application and assures the best possible way of remediating the phenol contaminated soil.

Biodegradation of phenol at high concentration by a novel fungal strain Paecilomyces variotii JH6

A novel phenol-degrading filamentous fungus, strain JH6, was isolated from activated sludge and identified as a member of Paecilomyces variotii based on standard morphological and phylogenetic analysis. The degradation assays suggested that the strain was able to utilize phenol as the sole source of carbon and energy at concentrations up to 1800 mg/l. The strain exhibited optimum phenol degradation performance with the addition of 100 mg/l glucose at pH 5, 37°C. Haldane's model could be fitted to the growth kinetics data well over a wide range of initial phenol concentrations (100-1800 mg/l), with kinetic values μ(max)=0.312 h(-1), K(s)=130.4 mg/l, and K(i)=200 mg/l. The decay coefficient was found to be 0.0073 h(-1). Complete phenol degradation by strain JH6 could be achieved in the presence of other toxicants, such as m-cresol and quinoline, which were often found in the real phenol-containing wastewater.

Performance of pulsed plate bioreactor for biodegradation of phenol

Biodegradation of phenol was carried out using Nocardia hydrocarbonoxydans immobilised on glass beads, in a pulsed plate bioreactor. The effect of operating parameters like frequency of pulsation and amplitude of pulsation on the performance of pulsed plate bioreactor for biodegradation of phenol in a synthetic wastewater containing 500ppm phenol was studied. Axial concentration profile measurements revealed that the pulsed plate bioreactor shows continuous stirred tank behaviour. As the amplitude was increased, percentage degradation increased, reaching 100% at amplitude of 4.7cm and higher. Introduction of pulsation is found to increase the percentage degradation. Percentage degradation has increased with increase in frequency and 100% degradation was achieved at 0.5s(-1) and above. Biofilms developed in a non-pulsed bioreactor were thicker than those in the pulsed plate bioreactor. But biofilm thickness remained almost constant with increasing frequency. Biofilm density was found to be influenced by pulsation. The time required to reach steady state was more for pulsed reactor than the non-pulsed reactor and this start-up time had increased with increase in frequency of pulsation. The performance studies reveal that the pulsed plate bioreactor with immobilized cells has the potential to be an efficient bioreactor for wastewater treatment.

Effect of long-term exposure, biogenic substrate presence, and electron acceptor conditions on the biodegradation of multiple substituted benzoates and phenolates

Biodegradation rates of benzoate and related aromatic compounds, 3-nitrobenzoate, 4-chlorobenzoate, 4-chlorophenol, and 2,4-dichlorophenol by unexposed (unacclimated) and long-term exposed (acclimated) biomass were quantified using a modified fed-batch technique. The acclimated biomass was taken after approximately 1-year of operation from three lab-scale sequencing batch reactors (SBR). These reactors were operated under various cycling electron acceptor conditions with a continuous feed of a synthetic wastewater containing biogenic and nonbiogenic chemicals including benzoate, 3-nitrobenzoate, and 4-chlorophenol, but not 4-chlorobenzoate or 2,4-dichlorophenol. The unexposed biomass was taken from a full-scale wastewater treatment plant, which constituted one of the original sources of inoculum for the lab-scale SBRs. The acclimated biomass manifested high removal rates of benzoate and related aromatic compounds with additional removal of structurally similar chemicals (4-chlorobenzoate and 2,4-dichlorophenol). The unacclimated biomass showed no removal of 3-nitrobenzoate, 4-chlorobenzoate or 2,4-dichlorophenol. Addition of biogenic substrates reduced the degradation of most aromatic compounds tested, but it enhanced 2,4-dichlorophenol removal. Biodegradation rates of each aromatic compound with the biomass from the anoxic/aerobic SBR were further determined under anaerobic (absence of aeration and NO3-), anoxic (no aeration, but with surplus NO3-), standard oxygen (DO > 0.2 mg/L), and elevated oxygen (DO > 25 mg/L) conditions. The removal rate of both benzoate and 3-nitrobenzoate decreased under anaerobic condition but not under the anoxic condition; 4-chlorophenol biodegradation, on the other hand, was reduced significantly under both anoxic and anaerobic conditions. The removal rates of aromatic compounds, particularly those of 3-nitrobenzoate and 2,4-dichlorophenol, increased significantly under elevated dissolved oxygen conditions. Our results demonstrated that when the biochemical conditions shifted from oxygen-respiration to nitrate respiration, to anaerobiosis, the biodegradation rates of test aromatic compounds decreased or ceased.

Process development for degradation of phenol byPseudomonas putida in hollow-fiber membrane bioreactors

The degradation of phenol (100-2800 mg/L) by cells Pseudomonas putida CCRC14365 in an extractive hollow-fiber membrane bioreactor (HFMBR) was studied, in which the polypropylene fibers were prewetted with ethanol. The effects of flow velocity, the concentrations of phenol, and the added dispersive agent tetrasodium pyrophosphate on phenol degradation and cell growth were examined. It was shown that about 10% of phenol was sorbed on the fibers at the beginning of the degradation process. The cells P. putida fully degraded 2000 mg/L of phenol within 73 h when the cells were immobilized and separated by the fibers. Even at a level of 2800 mg/L, phenol could be degraded more than 90% after 95-h operation. At low phenol levels (< 400 mg/L) where substrate inhibition was not severe, it was more advantageous to treat the solution in a suspended system. At higher phenol levels (> 1000 mg/L), however, such HFMBR-immobilized cells could degrade phenol to a tolerable concentration with weak substrate-inhibition effect, and the degradation that followed could be completed by suspended cultures due to their larger degradation rate. The process development in an HFMBR system was also discussed.

Effect of organic solvents on the yield of solvent-tolerant Pseudomonas putida S12

Solvent-tolerant microorganisms are useful in biotransformations with whole cells in two-phase solvent-water systems. The results presented here describe the effects that organic solvents have on the growth of these organisms. The maximal growth rate of Pseudomonas putida S12, 0.8 h-1, was not affected by toluene in batch cultures, but in chemostat cultures the solvent decreased the maximal growth rate by nearly 50%. Toluene, ethylbenzene, propylbenzene, xylene, hexane, and cyclohexane reduced the biomass yield, and this effect depended on the concentration of the solvent in the bacterial membrane and not on its chemical structure. The dose response to solvents in terms of yield was linear up to an approximately 200 mM concentration of solvent in the bacterial membrane, both in the wild type and in a mutant lacking an active efflux system for toluene. Above this critical concentration the yield of the wild type remained constant at 0.2 g of protein/g of glucose with increasing concentrations of toluene. The reduction of the yield in the presence of solvents is due to a maintenance higher by a factor of three or four as well as to a decrease of the maximum growth yield by 33%. Therefore, energy-consuming adaptation processes as well as the uncoupling effect of the solvents reduce the yield of the tolerant cells.