Effects of glucose on phenol biodegradation by heterogeneous populations

The effect of the presence of more easily degradable alternative carbon sources on the biodegradation of toxic waste components is of great practical importance. In this work, a mixed phenol/glucose waste was fed to two heterogeneous populations acclimated to different conditions: one was acclimated to phenol as a sole source of carbon and one to a mixed phenol/glucose substrate. Batch substrate utilization experiments were performed under both growth and nonproliferating (no medium nitrogen source) conditions in order to assess substrate removal patterns at the levels of enzyme production and enzyme function. The results indicated that the substrate removal pattern exhibited by the cells was significantly influenced by the acclimation characteristics of the culture. The phenol acclimated cells showed an initial preference for phenol, but the presence of glucose hindered phenol removal rate under both growth and nonproliferating conditions. The cells acclimated to the mixed phenol/glucose waste demonstrated rapid initial glucose removal with a slower concomitant utilization of phenol; acclimation to the mixed waste evidently had a significant impact on the substrate removal pattern for this mixed substrate system.     

Biodegradation of phenol by bacterial strains from petroleum-refining wastewater purification plant

The ability of four strains of bacteria derived from a biological petroleum-refining wastewater purification plant to carry out the biodegradation of phenol was studied. Two of the strains belonging to the genus Pseudomonas were found to be characterised by high effectiveness of the removal of phenol which was used as sole carbon and energy source (the strains were designated P1 and P2). In turn the effect of inoculum size, initial concentration of substrate (500 and 1,000 mg phenol/L) and temperature (10, 20 and 30 degrees C) on the rate of phenol degradation by strains P1, P2 and mixture of both was investigated. It was found that strain P1 which was identified as Pseudomonas fluorescens degraded phenol better than strain P2--Pseudomonas cepacia. The rate of phenol biodegradation was significantly affected by size of inoculum and temperature of incubation. Phenol was removed the fastest with the highest inoculum used. The optimal temperature was about 20 degrees C. At 10 and 30 degrees C the process of biodegradation was visibly inhibited. The rate of phenol utilisation was also found to decrease with increased concentration of substrate.     

Biodegradation of phenolic industrial wastewater in a fluidized bed bioreactor with immobilized cells of Pseudomonas putida

The paper presents the main results obtained from the study of the biodegradation of phenolic industrial wastewaters by a pure culture of immobilized cells of Pseudomonas putida ATCC 17484. The experiments were carried out in batch and continuous mode. The maximum degradation capacity and the influence of the adaptation of the microorganism to the substrate were studied in batch mode. Industrial wastewater with a phenol concentration of 1000 mg/l was degraded when the microorganism was adapted to the toxic chemical. The presence in the wastewater of compounds other than phenol was noted and it was found that Pseudomonas putida was able to degrade these compounds. In continuous mode, a fluidized-bed bioreactor was operated and the influence of the organic loading rate on the removal efficiency of phenol was studied. The bioreactor showed phenol degradation efficiencies higher than 90%, even for a phenol loading rate of 0.5 g phenol/ld (corresponding to 0.54 g TOC/ld).     

Effect of Co‐Substrates on Aerobic Phenol Degradation by Acclimatized and Non‐acclimatized Enrichment Cultures

Aerobic degradation of 7 mmol/L phenol in the presence of alternative carbon sources (7 mmol/L glucose or acetate or 1–2 mmol/L 2‐chlorophenol) was investigated using non‐acclimatized and acclimatized sewage sludges and enrichment cultures. The substrates represented an intermediate of phenol degradation (acetate), an independent substrate (glucose) or a “precursor‐substrate” of phenol degradation (2‐chlorophenol). Bacteria from sewage sludge, not pre‐adapted to phenol (2 mmol/L), rapidly respired acetate and glucose in the presence of phenol, whereas phenol was only bioconverted to any unknown aromatic metabolite after 24 h. In the presence of phenol and 2‐chlorophenol, no removal of both substances was observed when using the unacclimatized sludge. Sludge that was acclimatized to the degradation of phenol showed an initial preference for easily degradable co‐substrates such as glucose or acetate with only a slow concomitant respiration of phenol. Respiration of phenol increased rapidly after the co‐substrates were depleted. The highest phenol degradation rates were 51.6 mmol/L d, when phenol was the sole carbon substrate. Vice versa, phenol was preferentially respired in the presence of a less easily degradable co‐substrate such as 2‐chlorophenol at a rate of around 7 mmol/L d. Further studies with an enrichment culture that was obtained after 7 successive transfers of phenol‐adapted sludge into mineral medium with phenol as the only carbon source indicated that the acetate and glucose‐degrading capabilities were diminished or almost completely lost. In these enrichment cultures, phenol degradation was not affected by the presence of glucose, but glucose was not degraded. In contrary, the presence of acetate slightly slowed down the phenol degradation rate of the enrichment culture. Growth of the microorganisms apparently occurred at the expense of phenol and acetate respiration. The result of this work may be of practical importance in determining the feeding strategy, which is the key factor for most biological wastewater treatment systems. When acetate was present together with phenol in a wastewater, the phenol degradation rates were influenced by acetate, since acetate was an intermediate of phenol degradation. Glucose as an “independent substrate” was apparently degraded by other bacteria via acetate, and in this way it also influenced the phenol degradation rates. Glucose‐degrading bacteria could be “washed out” from the acclimatized sludge during several transfers into mineral medium with phenol as the sole carbon source. If later on, glucose was added again, it remained undegraded and did not influence phenol degradation. 2‐Chlorophenol degradation also requires other bacteria than phenol degraders.     

Biodegradation of phenol and m-cresol in a batch and fed batch operated internal loop airlift bioreactor by indigenous mixed microbial culture predominantly Pseudomonas sp

An internal loop airlift reactor (ILALR) is developed and studied for biodegradation of phenol/m-cresol as single and dual substrate systems under batch and fed batch operation using an indigenous mixed microbial strain, predominantly Pseudomonas sp. The results showed that the culture could degrade phenol/m-cresol completely at a maximum concentration of 600mgl(-1) and 400mgl(-1), respectively. Batch ILALR study has revealed that phenol has been preferentially degraded by the microbial culture rather than m-cresol probably owing to the toxic effect of the later. Sum kinetic model evaluated the interaction between the phenol/m-cresol in dual substrate system, which resulted in a high coefficient of determination (R(2)) value >0.98). The fed batch results showed that the strain was able to degrade phenol/m-cresol with maximum individual concentrations 600mgl(-1) each in 26h and 37h, respectively. Moreover for fed batch operation, degradation rates increased with increase in feed concentration without any lag in the degradation profile.     

The effect of concentration of phenols on their batch methanogenesis

The biodegradability of phenol and six other phenolic compounds (o-, m-, and p-cresol, 2-, 3-, and 4-ethylphenol) was examined in batch methanogenic cultures. The effect of concentration of these alkyl phenols on the anaerobic biodegradation of phenol was also evaluated. The inoculum used in this study was cultivated in a continuous flow laboratory fermenter with phenol as the primary substrate. Phenol, at initial concentrations as high to 1400 mg/L was completely degraded to methane and carbondioxide after 350 hours incubation. Complete degradation of m- and p-cresol was also observed while the ethylphenols and o-cresol were not significantly degraded.At initial concentrations exceeding 600 mg/L, phenol inhibited the phenol-degrading microorganisms but not the methanogens. At about 600 mg/L, cresols reduced the rate of phenol degradation to 50% of that observed in a control culture containing only 200 mg/L phenol. Ethylphenols were more inhibitory than cresols. Phenol degrading microorganisms were more susceptible to inhibition by cresols and ethylphenols than were the methanogens. The inhibitory effects of the three isomers of cresol and ethylphenol did not vary with the isomer but rather with the substituted functional group.     

Biological phenol degradation in a gas-liquid-solid fluidized bed reactor

Biological phenol degradation was performed experimentally in a gas-liquid-solid fluidized bed bioreactor using a mixed culture of living cells immobilized on activated carbon particles. A comprehensive model was developed for this system utilizing double-substrate limiting kinetics. The model was used to simulate the effects of changing inlet phenol concentration and biofilm thickness on the rate of biodegradation for two different types of support particles. The model shows that gas-liquid mass transfer is the limiting step in the rate of phenol biodegradation when the phenol loading is high.     

Dynamics of biodegradation of 2,4-dichlorophenoxyacetate in the presence of glucose

It has been observed experimentally that the biodegradation of 2,4-dichlorophenoxyacetate (2,4-D) is inhibited by the presence of glucose. However, this effect is masked by the fact that larger concentrations of active biomass are produced when glucose is available. The implication of such a "mixed" growth in a continuous flow system is that much higher dilution rates can be applied for an efficient chlorinated-organic removal when other conventional substrates are present. The mean cell residence time is reduced and the area of stability of the process is extended into higher dilution rates, as well as into higher influent concentrations. Finally, the presence of the mixed substrate changes dramatically the "washout" conditions for both substrates. All these facts point out that the biodegradation of chlorinated organics is more efficient in a mixed substrate environment.     

Kinetics of phenol biodegradation in the presence of glucose

The kinetics of utilization of glucose, phenol, and their mixtures by Pseudomonas putida (ATCC 17514) were studied with a continuously aerated, jacketed batch reactor operating at 28 degrees C and pH 7.2. It was found that when glucose is the sole carbon and energy source, the culture utilizes it following Monod kinetics. When phenol is the sole carbon and energy source, the culture biodegrades it following Andrews (inhibitory) kinetics. When both glucose and phenol are present in the medium, the culture uses them simultaneously but with lower specific rates. Reduction of the specific substrate utilization rates indicates that the two substances are involved in a cross-inhibitory pattern which can be classified as uncompetitive. The values of the kinetic interaction constants suggest that glucose inhibits the specific rate of phenol removal much more than phenol inhibits the specific rate of glucose utilization. The results suggest that substitutable substrates which are dissimilar in origin and molecular structure may be involved in an uncompetitive cross-inhibitory interaction when they are simultaneously removed. It is also concluded that the use of easily degradable substrates may not enhance the per-unit amount of biomass removal of compounds which are classified as toxic. A general classification of kinetic interactions between substitutable resources is proposed. (c) 1996 John Wiley & Sons, Inc.     

Aerobic,phenol-induced TCE degradation in completely mixed,continuous-culture reactors

BothPseudomonas putida F1 and a mixed culture were used to study TCE degradation in continuous culture under aerobic, non-methanotrophic conditions. TCE mass balance studies were performed with continuous culture reactors to determine the total percent removed in the reactors, and to quantify the percent removed by air stripping and biodegradation. Adsorption of TCE to biomass was assumed to be negligible. This research demonstrated the feasibility of treating TCE-contaminated water under aerobic, non-methanotrophic conditions with a mixed-culture, continuous-flow system.Initially glucose and acetate were fed as primary substrates. Pnenol, which has been shown to induce TCE-degrading enzymes, was fed at a much lower concentration (20mg/L). Little degradation of TCE was observed when acetate and glucose were the primary substrates. After omitting glucose and acetate from the feed and increasing the phenol concentration to 50mg/L, TCE biotransformation was observed at a significant level (46%). When the phenol concentration in the feed was increased to 420mg/L, 85% of the incoming TCE was estimated to have been biodegraded. Under the same conditions, phenol utilization by the mixed culture was greater than that ofP. putida F1, and TCE degradation by the mixed culture (85%) exceeded that ofP. putida F1 (55%). The estimated percent-of-TCE biodegraded by the mixed culture was consistently greater than 80% when phenol was fed at 420mg/L. Biodegradation of TCE was also observed in mixed-culture, batch experiments.     

Enhancement of biodegradation of phenol and a nongrowth substrate 4-chlorophenol by medium augmentation with conventional carbon sources

The enhancement of biodegradation of phenol and 4-chlorophenol (4-cp) as a cometabolised compound by Pseudomonas putida ATCC 49451 was accomplished by augmenting the medium with conventional carbon sources such as sodium glutamate and glucose. Compared with phenol as the sole carbon source, the addition of 1 gl(-1) sodium glutamate increased the toxicity tolerance of cells toward 4-cp and significantly improved the biodegradation rates of both phenol and 4-cp even when the initial concentration of 4-cp was as high as 200 mgl(-1). On the other hand, supplementation of glucose caused a significant drop in the medium pH from 7.2 to 4.3 resulting in a reduction of degradation rate, leaving a considerable amount of 4-cp undegraded when the initial concentration of 4-cp was higher than 100 mgl(-1). By regulating the pH of the medium, however, enhancement of degradation rates of phenol and 4-cp in the presence of glucose was achieved with a concomitant complete degradation of phenol and 4-cp.     

Enhancement of biodegradation of phenol and a nongrowth substrate 4-chlorophenol by medium augmentation with conventional carbon sources

The enhancement of biodegradation of phenol and4-chlorophenol (4-cp) as a cometabolised compound byPseudomonas putida ATCC 49451 was accomplishedby augmenting the medium with conventional carbonsources such as sodium glutamate and glucose. Comparedwith phenol as the sole carbon source, the addition of1 gl^-1 sodium glutamate increased the toxicitytolerance of cells toward 4-cp and significantlyimproved the biodegradation rates of both phenol and4-cp even when the initial concentration of 4-cp wasas high as 200 mgl^-1. On the other hand,supplementation of glucose caused a significant dropin the medium pH from 7.2 to 4.3 resulting in areduction of degradation rate, leaving a considerableamount of 4-cp undegraded when the initialconcentration of 4-cp was higher than 100 mgl^-1.By regulating the pH of the medium, however,enhancement of degradation rates of phenol and 4-cp inthe presence of glucose was achieved with aconcomitant complete degradation of phenol and 4-cp.     

Versatility of fluorene metabolite (phenol) in fluorene biodegradation by a sulfate reducing culture

Biodegradability of fluorene and the versatility of fluorene metabolite (i.e. phenol) in fluorene biodegradation by a sulfate-reducing enrichment culture were investigated. Batch experiments (with 5 mg l⁻¹ fluorene) were designed via the central composite design to examine the effects of sulfate (5-35 mM) and biomass (5-50 mg l⁻¹) concentrations (variables) on fluorene degradation (response). The experimental results revealed that fluorene removal was more influenced by the biomass concentration than the sulfate concentration. The optimal sulfate and biomass concentrations for fluorene biodegradation (90% removal) were found to be 14.4 mM and 37.8 mg l⁻¹, respectively. Under the optimal conditions, a set of biodegradation experiments were repeated to evaluate both the biodegradability of fluorene metabolite and the potential effect of phenol accumulation on fluorene degradation. The outcomes indicated a slow phenol degradation rate, i.e. 0.02 mg l⁻¹ d⁻¹. Moreover, a small reduction in the fluorene biodegradation efficiency was observed in the presence and accumulation of phenol. However, this sulfate reducing culture is a valuable resource for the simultaneous degradation of fluorene and phenol.     

Microbial biodegradation of cellophase.

The microbial biodegradation of cellophane (U.C.B.--Division Sidac) was studied. Preliminary experiments with pure cultures of seven cellulolytic microorganisms (Aspergillus sp., Penicillium sp., Chaetomium crispatum, Ch. globosum, Sclerotium rolfsii and two actinomycetes) revealed that the substrate as such was very recalcitrant, probably due to the occurrence of insoluble coating agents. Therefore, mixed cultures of the above mentioned cellulolytic microorganisms were used as inoculum. The cellophane showed a slow microbial degradation which starts only after 37 days of incubation. This long lag-phase is due to the unaltered presence of the coating agents. However, when the coating agents are extracted with tetrahydrofuran, the biodegradation starts after 10 days, resulting in a biodegradation rate of 85% after 52 days of incubation and a protein content of 30%. The endproduct (30% protein, 60% soluble sugars, 10% residual substrate) will probably be useful as compost.     

Modeling substrate interactions during the biodegradation of mixtures of toluene and phenol by Burkholderia species JS150

The biodegradation kinetics of toluene, phenol, and a mixture of toluene and phenol by Burkholderia species JS150 was measured and modeled. Both of these compounds can serve as the sole source of carbon and energy for this microorganism. The single-substrate biodegradation kinetics was described well using the Monod model, with model constants of mu(max,T) = 0.39 h(-1) and K(S,T) = 0.011 mM for growth on toluene and mu(max,P) = 0.309 h(-1) and K(S,P) = 0.0054 mM for growth on phenol. Degradation of the mixture of toluene and phenol followed simultaneous utilization kinetics with toluene being the preferred substrate. Toluene was found to inhibit the rate of utilization of phenol while the presence of phenol had little effect on the rate of degradation of toluene. Of the kinetic models that were tested, one developed for microbial degradation of multiple substrates was able to describe substrate interactions and to model the mixture utilization by strain JS150. Simple competitive, noncompetitive, or uncompetitive substrate kinetics were not sufficient to describe the observed inhibitory interactions.     

Anaerobic biodegradation of phenol by <Emphasis Type="Italic">Candida albicans</Emphasis> PDY-07 in the presence of 4-chlorophenol

Biodegradation of phenol and 4-chlorophenol (4-cp) using pure culture of Candida albicans PDY-07 under anaerobic condition was studied. The results showed that the strain could completely degrade up to 1,800 mg/l phenol within 68 h. The capacity of the strain to degrade phenol was higher than that to degrade 4-cp. In the dual-substrate system, 4-cp intensely inhibited phenol biodegradation. Comparatively, low-concentration phenol from 25 to 150 mg/l supplied a carbon and energy source for Candida albicans PDY-07 in the early phase of biodegradation and accelerated the assimilation of 4-cp, which resulted in that 50 mg/l 4-cp was degraded within less time than that without phenol. While the biodegradation of 50 mg/l 4-cp was inhibited in the presence of 200 mg/l phenol. In addition, the intrinsic kinetics of cell growth and substrate degradation were investigated with phenol and 4-cp as single and dual substrates in batch cultures. The results demonstrated that the models adequately described the dynamic behaviors of biodegradation by Candida albicans PDY-07.     

Effect of mineral nutrients on the kinetics of methane utilization by methanotrophs

The effect of different mineral nutrients on the kinetics of methane biodegradation by a mixed culture of methanotrophic bacteria was studied. The substrate factors examined were ammonia, iron, copper, manganese, phosphate, and sulphide. The presence of iron in the growth medium had a strong effect on the yield coefficient. Yield coefficients up to 0.49 mg protein per mg methane were observed when iron was added at concentrations of 0.10–5.0 mg/l. Iron addition also increased the maximum methane utilization rate. The same effect was observed after addition of ammonium to a medium where nitrate was the only nitrogen source. The observed Monod constant for methane utilization increased with increasing concentration of ammonia. This shows that ammonia is a weak competitive inhibitor as observed by other researchers. Relatively high levels of both ammonia (70 mg/l) and copper (300 µg/l) inhibited the methane degradation, probably due to the toxic effect of copper-amine complexes.     

Effect of substrate concentration on biodegradation of 2,4-dichlorophenol using modified rotating biological contactors

2,4-Dichlorophenol used in the manufacture of pesticides, germicides, resins, seed disinfectants and antiseptics, if disposed untreated causes greater havoc for land and aquatic environment. In all the earlier works, 2,4-dichlorophenol has been fed along with easily biodegradable substrate, glucose as one of the constituents. A modified 4-stage RBC was used for the biodegradation studies of 2,4-dichlorophenol. The micro organisms attached to the disks were specially acclimatised to the extent that the 2,4-dichlorophenol alone serves as the sole carbon source supporting their metabolic activities. The RBC was operated at 12?rpm. The toxic substrate removal studies were carried out in the hydraulic loading rates ranging from 0.005?m³/m²/d to 0.035?m³/m²/d and organic loading rates from 0.35?g/m²/d to 6.15?g/m²/d. A correlation plot between 2,4-dichlorophenol removal and organic loading rate is presented. A mathematical model is proposed using regression analysis.     

Rate of Biodegradation of Phenol by Klebsiella oxytoca in Minimal Medium and Nutrient Broth Conditions

The rate of biodegradation of phenol by Klebsiella oxytoca strain was studied in the nutrient broth and M9 minimal medium. It was found that K. oxytoca degrade phenol at elevated phenol concentration where 75% of initial phenol concentration of 100 ppm will degrade within 72 h. This rate was increased with increasing the initial cell densities, increasing the aeration rate and increasing the time required for complete degradation. At phenol concentration above 400 ppm, the cells were unable to degrade the substrate efficiently due to the increasing concentration of phenol in the medium. The culture conditions were also showed a significant impact on the ability of these cells to remove phenol. The optimum solution pH and temperature were 6.8 and 37°C, respectively. The growth of these cells in the presence and absence of phenol was modeled and it was found that the Recatti equation best fit the growth in the absence of phenol whereas the Voltera equation accounted for the history of the cell population in the presence of phenol.