Glycine-β-cyclodextrin-assisted cometabolism of phenanthrene and pyrene by Pseudomonas stutzeri DJP 1 from marine sediment

Cometabolic degradation is currently an effective and extensively way to remove high molecular weight polycyclic aromatic hydrocarbons(HMW-PAHs).Unfortunately,due to low bio-accessibility and high biotoxicity,the cometabolic degradation rate of HMW-PAHs is limited.Glycine-β-cyclodextrin(GCD)was obtained through amino modification ofβ-cyclodextrin(BCD)and added to cometabolic system of phenanthrene(PHE)and pyrene(PYR)to assist PYR biodegradation.Results show that the addition of GCD(100 mg/L)effectively improved the removal rate of PYR(20 mg/L)by 42.3%.GCD appeared to increase the bio-accessibility and reduce the biotoxicity of PHE and PYR,and then promoted the growth of Pseudomonas stutzeri DJP1 and stimulated the elevation of dehydrogenase(DHA)and catechol 12 dioxygenase(C12O)activities.The phthalate metabolic pathway was accelerated,which improved the cometabolic degradation.This study provided a new reference for the cometabolic degradation of HMW-PAHs.

Biodegradation of malathion by Acinetobacter johnsonii MA19 and optimization of cometabolism substrates

To enhance the removal efficiency of malathion in the wastewater from organophosphate pesticide mill, a bacterium, Acinetobacter johnsonii MA19, that could degrade malathion with cometabolisrn was isolated from malathion-polluted soil samples using enrichment culture techniques. Four kinds of additional compounds, sodium succinate, sodium acetate, glucose, and fructose were tested to choose a favorite carbon source for the cometabolism of strain MA19. The results showed that sodium succinate and sodium acetate could promote malathion biodegradation and cell growth. The investigation results of the effects of sodium succinate concentrations on the malathion biodegradation indicated that the more sodium succinate supplied resulted in quick degradation of malathion and fast ceils multiplied. Zero-order kinetic model was appropriate to describe the malathion biodegradation when the concentration of sodium succinate was more than 0.5144 g/L, The degradation rate constant （K） reached the maximum value of 3.5837 mg/（L·h） when the mass ratio of sodium succinate to malathion was 128.6 mg/mg. The aquatic toxicity of the malathion was evaluated using the test organism, Limnodrilus hoffmeisteri. The data obtained suggested that the toxicity of malathion could be ignored after 84 h biodegradation. Our result demonstrates the potential for using bacterium A. johnsonii MA19 for malathion biodegradation and environmental bioremediation when some suitable conventional carbon sources are supplied.

A review:Advances in microbial remediation of trichloroethylene (TCE)

Research works in the recent past have revealed three major biodegradation processes leading to the degradation of trichloroethylene. Reductive dechlorination is an anaerobic process in which chlorinated ethenes are used as electron acceptors. On the other hand, cometabolism requires oxygen for enzymatic degradation of chlorinated ethenes, which however yields no benefit for the bacteria involved. The third process is direct oxidation under aerobic conditions whereby chlorinated ethenes are directly used as electron donors by microorganisms. This review presented the current research trend in understanding biodegradation mechanisms with regard to their field applications. All the techniques used are evaluated, with the focus being on various factors that influence the process and the outcome.

Anaerobic BTEX degradation in soil bioaugmented with mixed consortia under nitrate reducing conditions

Different concentrations of BTEX, including benzene, toluene, ethylbenzene, and three xylene isomers, were added into soil samples to investigate the anaerobic degradation potential by the augmented BTEX-adapted consortia under nitrate reducing conditions. All the BTEX substrates could be anaerobically biodegraded to non-detectable levels within 70 d when the initial concentrations were below 100 mg/kg in soil. Toluene was degraded faster than any other BTEX compounds, and the high-to-low order of degradation rates were toluene 〉 ethylbenzene 〉 m-xylene 〉 o-xylene 〉 benzene 〉 p-xylene. Nitrite was accumulated with nitrate reduction, but the accumulation of nitrite had no inhibitory effect on the degradation of BTEX throughout the whole incubation. Indigenous bacteria in the soil could enhance the BTEX biodegradation ability of the enriched mixed bacteria. When the six BTEX compounds were simultaneously present in soil, there was no apparent inhibitory effect on their degradation with lower initial concentrations. Alternatively, benzene, o-xylene, and p-xylene degradation were inhibited with higher initial concentrations of 300 mg/kg. Higher BTEX biodegradation rates were observed in soil samples with the addition of sodium acetate compared to the presence of a single BTEX substrate, and the hypothesis of primary-substrate stimulation or cometabolic enhancement of BTEX biodegradation seems likely.

Cometabolic microbial degradation of trichloroethylene in the presence of toluene

Trichloroethylene(TCE), a common groundwater pollutant, was cometabolized by microorganisms in the presence of toluene as a growth substrate. The effect of concentrations of toluene and TCE and temperature on biodegradation was discussed. Acclimated microorganisms degraded TCE after a lag period of 5 to 22 h depending on toluene concentrations. Approximately 60%, 90% and 64% of TCE were degraded at toluene to TCE concentration ratios of 23∶1, 115∶1 and 230∶1, respectively. At a TCE concentration of 1 46 μg/ml, 80% of TCE and 98 4% of toluene were removed. But less degradation of TCE and toluene was observed when TCE concentration was above 48 8 μg/ml. The lag time of TCE decreased and the TCE biodegradation rates increased with the increase of temperature.

Releasing nitrogen from ammoniated lignin by white rot fungus cometabolizes environmental pollutants

The nitrogen modified lignocelluloses(NML) produced under oxic ammoniation was metabolized by white rot fungus, NH + 4 N was released, NO - 3 N concentration was decreased and total nitrogen loss was blocked within incubation period. During releasing nitrogen from the metabolism of NML, white rot fungus cometabolized recalcitrant environmental pollutants and showed higher degradation capability. Results indicated that this NML complex colonized by white rot fungus might be effective with economic feasibility when they are applied into the vast field ecosystem, it might stabilize NH + 4 nitrogen flux and bioremediate the polluted environmental sites.

Microbial Community from MTBE-Contaminated Soil for Aerobic Biodegradation of MTBE

This Methyl tert-butyl ether (MTBE) is one of the main additives in gasoline to increase octane rating and consequently reduce air pollution. The physico-chemical properties of this substance (high water solubility, low sorption in soil) result in high mobility and considerable concentrations in aquifers. In this survey, Isfehan Refinery that was encountered with MTBE contamination problem was selected as a case study and the MTBE degradation ability of this contaminated area by its indigenous microorganisms was investigated. In the first step of this survey, the influence of various factors on the aerobic degradation of MTBE such as mixed culture type, incubation time, microbial culture and optimal concentration of MTBE were investigated in shaking flasks and the most important factors were specified by means of fractional factorial design 1/2. In the second stage by using optimal values which obtained from the first stage, the effects of co-substare parameter and inoculum parameter were assayed by means of response surface method. The results of the experiments showed that the mixed culture type and initial concentration of MTBE were the most significant factors. The results of the experiments showed that the mixed indigenous culture acted better than activated sludge. The initial concentration of MTBE was also one of the most significant factors. At the best condition about 31 percent of MTBE was treated by co-substrating with n-hexane in a ratio of 0.2.

Kinetics of cometabolic degradation of 2-chlorophenol and phenol by Pseudomonas putida

In order to address the complex cometabolic degradation of toxic compounds, batch experiments on the biodegradation of 2-chlorophenol （2-CP） and phenol by Pseudomonas putida were carried out. The experimental results show that 2-CP has an inhibitory effect on cell growth and phenol degradation, which demonstrates that the interaction between substrates affects cell growth and substrate degradation. A kinetic model of cell growth and substrate transformation was also developed. The square of the correlation coefficient from the experiment was 0.97, indicating that this model properly simulates the cometabolic degradation of 2-CP and phenol.

Cometabolic degradation of veratryl alcohol and biphenyl by white rot fungus under nitrogen nutrition-rich condition

In this paper, changes of enzymes involved in the degradation of recalcitrant aromatic pollutants from white rot fungus Phlebia radiata I 5 6 and cometabolism of biphenyl and varatryl alcohol by this fungus under nitrogen nutrition rich were studied. Results from the experiment showed that C/N concentration ratio in the culture media played an important role on the activity of LiP. Under the condition of high concentration ratio of C/N or N/C, activity of LiP was higher, but higher activity of MnP only followed the low concentration of glucose or tartrate ammonium concentration in the media, when concentration of glucose or tartrate ammonium was more than 0 01 mol/L, the activity of MnP dropped down quickly. Veratryl alcohol increased the activity of LiP and MnP as well as the amount of ·OH radical free under different concentration of nitrogen or carbon source; ascorbic acid, a scavenger of ·OH radical free, brought the opposite effect to that of the veratryl alcohol on the LiP and MnP activity. Under nitrogen nutrition rich condition removal percentage of biphenyl was lower, however, under cometabolic condition of veratryl alcohol and biphenyl, the degradation was enhanced obviously, moreover, intermediate products accumulated in the media during the cometabolic degradation process of biphenyl and veratryl alcohol was different from these which was found in the process of separate degradation of biphenyl or veratryl alcohol.

Biodegradation of Tetrachlorothylene Using Methanol as Co-metabolic Substrate

Objective To investigate the biodegradation of tetrachloroethylene （PCE） using methanol as electron donor by acclimated anaerobic sludge. Methods HP-6890 gas chromatograph （GC）, together with HP-7694 autosarnpler, was used to analyze the concentration of PCE and intermediates. Results PCE could be decholrinated reductively to DCE via TCE, and probably further to VC and ethylene. The degradation of PCE and TCE conformed to first-order reaction kinetics. The reaction rate constants were 0.8991 d^-1 and 0.068 d^-1, respectively, and the corresponding half-life were 0.77 d and 10.19 d, respectively. TCE production rate constant was 0.1333 d^-1, showing that PCE was degraded more rapidly than TCE. Conclusion Methanol is an electron donor suitable for PCE degradation and the cometabolic electron donors are not limiting factors for PCE degradation.

Anaerobic Removal of Trace Organic Contaminants in Sewage Sludge: 15 Years of Experience

Trace organic contaminants (TOCs) correspond to a broad range of molecules generated either directly or indirectly by human activity. Even though TOCs are found at low concentrations in the environment, they often accumulate by biomagnification and bioaccumulation into biological organisms and cause irreversible damages in biological systems through direct or indirect toxic effects such as endocrine disruption and tumour initiation. This manuscript presents the main findings of over fifteen years of research focusing on biological removal of various TOCs found in sewage sludge from urban treatment plants. A special focus of the research was made on microbial processes in complex anaerobic ecosystems. Four families of compounds mostly retrieved in urban plants were studied: the polycyclic aromatic hydrocarbons (PAHs), the polychlorobiphenyls (PCBs), the phthalic acid esters (PAEs), and the nonylphenol ethoxylates (NPEs). It was observed that the microbial capability for removing low amounts of TOCs required a long adaptation time and was often limited by the bioavailability of these compounds. In fact, the overall biodegradation resulted from the numerous interactions existing between the matrix (organic matter) and the microbial ecosystems according to the physico-chemical sorption properties of these compounds. Mechanistic aspects were also tackled in depth and specific models were developed for better understanding the network of interactions between TOCs, microorganisms, and organic matter. These findings could be extrapolated to other ecosystems such as soils and sediments. Finally, it was shown that microbial cometabolism was essential for TOC removal, and the concept of bioavailability was not only dependent on the nature, the level, and the sorption properties of TOCs but was also strongly dependent on the nature and the concentration of the sludge organic matter. Specific parameters were proposed for better evaluating the fate of TOCs in microbial anaerobic processes and technological solutions for efficient removal of these compounds were also proposed.

Effect of Granular Activated Carbon on the Enhancement of Cometabolic Biodegradation of Phenol and 4-Chlorophenol

Enhancement of the cometabolic biotransformation of 4-chlorophenol（4-cp） and phenol were studied using chemically and thermally granular activated carbons（GACs）.It was found that both chemically activated and thermally activated GAC effectively adsorb phenol and 4-cp.More than 80% adsorped substrates were later desorpted,showing a reversible sorption behaviour in the GAC.For each activated carbon type,4-cp was preferentially adsorbed over phenol and the desorption efficiencies of both phenol and 4-cp were found to increase linearly with the initial mass of adsorbate in the adsorbent.The biodegradation of 500 mg/L phenol by Pseudomonas putida took 24 h while the biodegradation of 4-cp took 32 h.Inhibitions during the cometabolic biodegradation of 4-cp and phenol were alleviated by the addition of the GACs.The system with chemically-activated coconut type GAC had better system stability over thermally-activated peat type GAC.The results show that GAC can be regenerated by the cells enhancement of the cometabolic biotransformation of 4-cp and phenol can be accomplished using chemically-activated coconut type GAC.