Biodegradation of phenol and cresol isomer mixtures by Arthrobacter

Abstract: Biodegradation of phenol and m- cresol using a pure culture of Candida tropicalis was studied. The results showed that C. tropicalis could degrade 2000 mg l −1 phenol alone and 280 mg l −1 m -cresol alone within 66 and 52 h, respectively. The capacity of the strain to degrade phenol was obviously higher than that to degrade m -cresol. The presence of m -cresol intensely inhibited phenol biodegradation. Only 1000 mg l −1 phenol can be completely degraded in the presence of 280 mg l −1 m -cresol. On the contrary, the phenol of low concentration from 100 to 500 mg l −1 supplied a sole carbon and energy source for C. tropicalis in the initial phase of biodegradation and accelerated the assimilation of m -cresol, resulting in the fact that m -cresol biodegradation velocity was higher than that without phenol. Besides, the capacity of C. tropicalis for m -cresol biodegradation was increased up to 320 mg l −1 with the presence of 60–100 mg l −1 phenol. In addition, the intrinsic kinetics of cell growth and substrate degradation were investigated with phenol and m- cresol as single and mixed substrates in batch cultures. The results illustrated that the models proposed adequately described the dynamic behaviors of biodegradation by C. tropicalis .

Abstract: Aromatic compounds are widely distributed in nature and free phenols are frequently liberated as metabolic intermediates during the degradation of plant materials. In recent years the natural supply of phenolic substances has been greatly increased due to the release of industrial byproducts into the environment. Effluents from petrochemical, textile and coal industries contain phenolic compounds in very high concentration; therefore there is a necessity to remove phenolic compounds from the environment. Among various techniques available for removal of phenols, biodegradation is an environment friendly and cost effective method. This paper describes about the various sources of phenol, various microorganisms involved in the biodegradation including aerobe and anaerobe, effect of environmental parameters on phenol degradation and kinetic analysis of biodegradation, and various

Abstract: A phenol-degrading microorganism, Alcaligenes faecalis , was used to study the substrate interactions during cell growth on phenol and m -cresol dual substrates. Both phenol and m -cresol could be utilized by the bacteria as the sole carbon and energy sources. When cells grew on the mixture of phenol and m -cresol, strong substrate interactions were observed. m -Cresol inhibited the degradation of phenol, on the other hand, phenol also inhibited the utilization of m -cresol, the overall cell growth rate was the co-action of phenol and m -cresol. In addition, the cell growth and substrate degradation kinetics of phenol, m -cresol as single and mixed substrates for A. faecalis in batch cultures were also investigated over a wide range of initial phenol concentrations (10–1400 mg L −1 ) and initial m -cresol concentrations (5–200 mg L −1 ). The single-substrate kinetics was described well using the Haldane-type kinetic models, with model constants of μ m 1 = 0.15 h −1 , K S 1 = 2.22 mg L −1 and K i 1 = 245.37 mg L −1 for cell growth on phenol and μ m 2 = 0.0782 h −1 , K S 2 = 1.30 mg L −1 and K i 2 = 71.77 mgL −1 , K ′ i 2 = 5480 ( mg L − 1 ) 2 for cell growth on m -cresol. Proposed cell growth kinetic model was used to characterize the substrates interactions in the dual substrates system, the obtained parameters representing interactions between phenol and m -cresol were, K = 1.8 × 10 −6 , M = 5.5 × 10 −5 , Q = 6.7 × 10 −4 . The results received in the experiments demonstrated that these models adequately described the dynamic behaviors of phenol and m -cresol as single and mixed substrates by the strain of A. faecalis.

Abstract: With the development of industrial production and continuous demand for chemicals, a large volume of wastewater containing phenols was discharged into the aquatic environment. Moreover, chemical leakage further increased the emission of phenols into aquatic systems. Phenol and its methylated derivative (cresols) were selected due to their extensive use in industry and ecotoxicity to freshwater and marine organisms. This review focused on the ecotoxicity of phenol and m-, o-, and p-cresol on aquatic systems. The mechanism of action of phenols was also discussed. The aim of this literature review was to summarise the knowledge of the behaviour, and toxicity on marine and freshwater organisms, of phenols as well as to try to select a series of sensitive biomarkers suitable for ecotoxicological assessment and environmental monitoring in aquatic environments.

Abstract: Phenolic compounds are hazardous pollutants known to be toxic at low concentration. Removal of phenols from industrial wastewater streams before their discharge into receiving water bodies is thus obligatory. Numerous phenol-degrading non-halophilic bacterial isolates have been described, but detailed information regarding phenol degradation by halophiles is rather sparse. Here we report a new phenol-degrading halophilic bacterium isolated from a hypersaline soil. The bacterium was identified as Halomonas sp. strain PH2-2 using 16S rDNA sequence analysis (GenBank accession number HM543189 ). Strain PH2-2 was isolated by a multistep enrichment and screening techniques on mineral medium containing 100 mg l −1 of phenol as sole source of carbon. The strain was able to utilize phenol and p -cresol as sole source of carbon and energy but not nitrophenols and chlorophenols. The bacterium was able to degrade up to 1100 mg l −1 of phenol but cell growth was inhibited at higher phenol concentrations. The strain was able to remove phenol in media containing 18% NaCl but the removal efficiency decreased from 95% to 64% in comparison to media containing 7% NaCl. The results indicated the potential application of the strain PH2-2 for treatment of hypersaline phenol-containing industrial wastewaters.

Abstract: Benzene, toluene, and p-xylene (BTX) were degraded by indigenous mixed cultures in sandy aquifer material and by two pure cultures isolated from the same site. Although BTX compounds have a similar chemical structure, the fate of individual BTX compounds differed when the compounds were fed to each pure culture and mixed culture aquifer slurries. The identification of substrate interactions aided the understanding of this behavior. Beneficial substrate interactions included enhanced degradation of benzene and p-xylene by the presence of toluene in Pseudomonas sp. strain CFS-215 incubations, as well as benzene-dependent degradation of toluene and p-xylene by Arthrobacter sp. strain HCB. Detrimental substrate interactions included retardation in benzene and toluene degradation by the presence of p-xylene in both aquifer slurries and Pseudomonas incubations. The catabolic diversity of microbes in the environment precludes generalizations about the capacity of individual BTX compounds to enhance or inhibit the degradation of other BTX compounds.

Abstract: Two Pseudomonas species (designated strains B1 and X1) were isolated from an aerobic pilot-scale fluidized bed reactor treating groundwater containing benzene, toluene, and p-xylene (BTX). Strain B1 grew with benzene and toluene as the sole sources of carbon and energy, and it cometabolized p-xylene in the presence of toluene. Strain X1 grew on toluene and p-xylene, but not benzene. In single substrate experiments, the appearance of biomass lagged the consumption of growth substrates, suggesting that substrate uptake may not be growth-rate limiting for these substrates. Batch tests using paired substrates (BT, TX, or BX) revealed competitive inhibition and cometabolic degradation patterns. Competitive inhibition was modeled by adding a competitive inhibition term to the Monod expression. Cometabolic transformation of nongrowth substrate (p-xylene) by strain B1 was quantified by coupling xylene transformation to consumption of growth substrate (toluene) during growth and to loss of biomass during the decay phase. Coupling was achieved by defining two transformation capacity terms for the cometabolizing culture: one that relates consumption of growth substrate to the consumption of nongrowth substrate, and second that relates consumption of biomass to the consumption of nongrowth substrate. Cometabolism increased decay rates, and the observed yield for strain B1 decreased in the presence of p-xylene.

Abstract: Experimental observations indicate that the rates of cometabolic transformation are linked to the consumption of growth substrate during growth and to the consumption of cell mass and/or energy substrate in the absence of growth substrate. Three previously proposed models (models 1 through 3) describing the kinetics of cometabolism by resting cells are compared, and the interrelationships and underlying assumptions for these models are explored. Models 1 to 3 are shown to converge at high concentrations of the nongrowth substrate. An expression describing nongrowth substrate transformation in the presence of growth substrate is proposed, and this expression is integrated with an expression for cell growth to give a single unstructured model (model 4) that encompasses models 1 to 3 and describes cometabolism by both resting and growing cells. Model 4 couples transformation of nongrowth substrate to consumption of growth substrate and biomass, and predicts that cometabolism will result, and decreased specific growth rates for a cometabolizing population. Competitive inhibition can also be incorporated in the model. Experimental aspects of model calibration and verification are discussed. The need for models that distinguish between the exhaustion of cell activity and cell death is emphasized. © 1993 Wiley & Sons, Inc.

Abstract: Rates of polycyclic aromatic hydrocarbon (PAH) degradation and mineralization were influenced by preexposure to alternate PAHs and a monoaromatic hydrocarbon at relatively high (100 ppm) concentrations in organic-rich aerobic marine sediments. Prior exposure to three PAHs and benzene resulted in enhanced [14C]naphthalene mineralization, while [14C]anthracene mineralization was stimulated only by benzene and anthracene preexposure. Preexposure of sediment slurries to phenanthrene stimulated the initial degradation of anthracene. Prior exposure to naphthalene stimulated the initial degradation of phenanthrene but had no effect on either the initial degradation or mineralization of anthracene. For those compounds which stimulated [14C]anthracene or [14C]naphthalene mineralization, longer preexposures (2 weeks) to alternative aromatic hydrocarbons resulted in an even greater stimulation response. Enrichment with individual PAHs followed by subsequent incubation with one or two PAHs showed no alteration in degradation patterns due to the simultaneous presence of PAHs. The evidence suggests that exposure of marine sediments to a particular PAH or benzene results in the enhanced ability of these sediments to subsequently degrade that PAH as well as certain other PAHs. The enhanced degradation of a particular PAH after sediments have been exposed to it may result from the selection and proliferation of specific microbial populations capable of degrading it. The enhanced degradation of other PAHs after exposure to a single PAH suggests that the populations selected have either broad specificity for PAHs, common pathways of PAH degradation, or both.

Abstract: This study dealt with the interactions with benzene degradation of the following aromatic compounds in a mixed substrate: toluene, o-xylene, naphthalene, 1,4-dimethylnaphthalene, phenanthrene, and pyrrole. The experiment was performed as a factorial experiment with simple batch cultures. The effect of two different types of inocula was tested. One type of inoculum was grown on a mixture of aromatic hydrocarbons; the other was grown on a mixture of aromatic hydrocarbons and nitrogen-, sulfur-, and oxygen-containing aromatic compounds (NSO compounds), similar to some of the compounds identified in creosote waste. The culture grown on the aromatic hydrocarbons and NSO compounds was much less efficient in degrading benzene than the culture grown on only aromatic hydrocarbons. The experiments indicated that toluene- and o-xylene-degrading bacteria are also able to degrade benzene, whereas naphthalene-, 1,,4-dimethylnaphthalene-, and phenanthrene-degrading bacteria have no or very little benzene-degrading ability. Surprisingly, the stimulating effect of toluene and o-xylene was true only if the two compounds were present alone. In combination an antagonistic effect was observed, i.e., the combined effect was smaller than the sum from each of the compounds. The reason for this behavior has not been identified. Pyrrole strongly inhibited benzene degradation even at concentrations of about 100 to 200 micrograms/liter. Future studies will investigate the generality of these findings.