Kinetics and mechanisms of p-nitrophenol biodegradation by Pseudomonas aeruginosa HS-D38

The kinetics and mechanisms of p-nitrophenol （PNP） biodegradation by Pseudomonas aeruginosa HS-D38 were investigated. PNP could be used by HS-D38 strain as the sole carbon, nitrogen and energy sources, and PNP was mineralized at the maximum concentration of 500 mg/L within 24 h in an mineral salt medium （MSM）. The analytical results indicated that the biodegradation of PNP fit the first order kinetics model. The rate constant kpNp is 2.039 ×10^-2/h in MSM medium, KeNp＋N is 3.603 × 10^-2/h with the addition of ammonium chloride and KPNP＋c is 9.74 ×10^-3/h with additional glucose. The addition of ammonium chloride increased the degradation of PNP. On the contrary, the addition of glucose inhibited and delayed the biodegradation of PNP. Chemical analysis results by thin-layer chromatography （TLC）, UV-Vis spectroscopy and gas chromatography （GC） techniques suggested that PNP was converted to hydroquinone （HQ） and further degraded via 1,2,4-benzenetriol （1 ,2,4-BT） pathway.

Transcriptomic analysis of molecular mechanisms underlying the biodegradation of organophosphorus pesticide chlorpyrifos by Lactobacillus delbrueckii ssp.bulgaricus in skimmed milk

Bioremediation of organophosphorus pesticides in contaminated foodstuffs using probiotics has been increasingly under the spotlight in recent years,though the biodegradation mechanism and derived intermediate products remain unclear.This study aimed to help fill this knowledge gap and examined the degradation mechanism of organophosphorus pesticide,chlorpyrifos,in milk by Lactobacillus delbrueckii ssp.bulgaricus using gas chromatography-tandem mass spectrometry(GC-MS/MS)combined with transcriptome analysis.After the strain was cultured for 20 h in the presence of chlorpyrifos,differential expressions of 383 genes were detected,including genes probably implicated during chlorpyrifos degradation such as those related to hydrolase,phosphoesterase,diphosphatase,oxidoreductase,dehydratase,as well as membrane transporters.GC-MS/MS analysis revealed the changes of secondary metabolites in L.bulgaricus during milk fermentation due to chlorpyrifos stress.6-Methylhexahydro-2H-azepin-2-one,2,6-dihydroxypyridine and methyl 2-aminooxy-4-methylpentanoate as intermediates,along with the proposed pathways,might be involved in chlorpyrifos biodegradation by L.bulgaricus.

Effects of biodegradation on diamondoid distribution in crude oils from the Bongor Basin,Chad

The sensitivity of biodegradation on diamondoids was investigated using a series of biodegraded oil samples from the Ronier tectonic unit of Bongor Basin,Chad.The results suggest that diamondoids,including adamantanes(As)and diamantanes(Ds),are relatively resistant to biodegradation and obvious biodegradation was observed in oils with a Peters-Moldowan(PM)biodegradation rank of 6 or more.Overall,the sensibility of biodegradation on diamondoids is generally similar to hopanes and regular steranes.As biodegradation evolves,the changes in concentration and components of diamondoids show that the biodegradation process is selective and stepwise.The significant increase of MD/MA and DMD/DMA for oils with a PM ranking 6^(+) indicates that diamantanes are generally more resistant to biodegradation than adamantanes.The similar trends of DMA/MA,EA/MA,MD/D,DMD/MD and other relevant indexes,show that higher alkylation homologs are more resistant to biodegradation.The commonly used diamondoid ratios,such as MAI,EAI,MDI and DMID-1,are obviously affected by biodegradation at the stage of high-level biodegradation,which may indicate that these ratios should be used with caution in case of severely degraded oils.

Biodegradation Potentials of Contaminated Soil around Ministry of Works Workshop Aba,Abia State,Nigeria

Global industrialization over the past centuries has resulted in widespread contamination of the environment with organic and inorganic wastes and their pattern of disposal.The study aimed at isolating fungi from spent diesel contaminated soil around Ministry of Works in Aba,Abia State for biodegradation potentials on the soil properties.About four(4)fungal species were isolated from the five(5)sites using cultural and biochemical characteristics.The isolate was screened,and optical density measured using spectrophotometer.A total of 5 soil samples from each location(0-15 cm and 15-30 cm)were collected and homogenized to have composite sample.Samples were taken to the laboratory for analysis of soil physiochemical parameters,fungi count and biodegradable potential of the fungi using standard methods.Data obtained revealed that,physical property of the soil such as sand(85.20%±0.01%),silk(6.4%±0.01%)were lower than the control location except clay(17.39%±0.01%).Chemical properties revealed highest concentration of element such as pH(4.76±0.01),total nitrogen(0.18%±0.011%),total organic carbon(3.41±0.01),sodium(0.21±0.01),potassium(0.24±0.001),magnesium(4.41±0.015),calcium(5.21±0.015),organic matter(6.18±0.011),and available phosphorus(30.99±0.01).All elements in the study site were higher than the control site with an exception to sodium(Na),which was lower.Fungi isolate identified were Aspergillus niger,Trichoderma virdae,Aspergillus flavus,and Pencillum corylophlum.The degradation potential of fungi identified shows that consortium degraded 29%of diesel oil from the soil followed by A.flavus,T.virdae,A.niger and the least was T.corylophlum.The study concludes that despite indiscriminate disposal of spent diesel oil,the nutrient content was still higher than control and consortium performed well in degradation.

Biodegradation of High Concentration of p-Nitrophenol （PNP） by Wastewater Microflora

Many nitrophenols tend to persist in the environment and they may become public health hazards. Among nitrophenols, p-nitrophenol （PNP） is a priority pollutant that has been widely used as pesticide. PNP is a toxic compound that enters the environment during manufacturing and processing of a variety of industrial products. This situation generalized its presence in multiple natural ecosystems： rivers, wastewaters, subterranean waters, soil treated by pesticides and urban atmosphere. This study aims to test the ability of wastewater microflora to degrade high concentration of PNP （500 rag/L） aerobically. An identification of the dominant microorganisms involved in the biodegradation is also carried. The cultures are performed using a minimum medium, where PNP is the sole source of carbon, energy and nitrogen. The kinetic of biodegradation is followed for more than 30 days of incubation at 30 ~C on a shaker （150 tours/min）. The obtained results show that more than 90% of PNP initial concentration is decomposed at the end of incubation. The isolation of microorganisms degrading PNP gave two bacterial colonies with different macroscopic aspects. Sequence analysis of 16S ribosomal DNA indicated that the PNP degrading isolates were closely related to members of the species： Pseudomonas aeruginosa and Bacillus cereus.

Processing of Aniline Aerofloat Wastewater with SBR System and Its Biodegradation Mechanism

ObjectiveThis study aimed to investigate the biodegradation effect and biodegradation mechanism of aniline aerofloat wastewater. MethodSmall-scale processing of simulated aniline aerofloat wastewater was carried out with SBR （Sequencing Batch Reactor） system; intermediate products in the process were analyzed using high-performance liquid chromatography. ResultAccording to the experimental results, the small-scale process was basically stably operated after 40 days of activation and regulation, leading to relatively ideal degradation effect on aniline aerofloat, the COD removal efficiency reached 64.3% , degradation rate of aniline aerofloat reached 93.4%, which could be applied in the treatment of mine flotation wastewater containing such pollutant. During the degradation process, pH increased from 5.83 to 6.60 and then dropped to 6.17, which might be caused by the thiocyanate ions and aniline generated in the degradation process. Aniline aerofloat mainly produced two preliminary products during the biodegradation process： aniline and a substance that was difficult to be biodegraded under aerobic conditions, which was the main reason for the relatively high COD value in effluent. Furthermore, aniline was eventually biodegraded. ConclusionThis study provided basis for the development of biological treatment of flotation wastewater in China and showed great significance for the improvement of ecological environment around the mines.

Isolation, Identification and Biodegradation Characteristics of a Phthalate Ester Degrading Bacterium

By using plate screening techniques with five phthalate esters （DMP, DEP, DBP, DEHP and DOP） as energy and carbon sources, an active strain was isolated from the sediments of Chaohu Lake, which was identified as Burkholderia pickettil and named B. pickettii.z-1. The biodegradation of five phthalate esters by B. pick- ettii.z-1 strain was in accordance with the pseudo first-order kinetic equation： Ct = C0.e-kt. As the concentration of phthalate esters increased, the degradation rate of phthalate esters was reduced. B. pickettii.z-1 strain exhibited remarkably different degradation effects on various PAEs. Specifically, short-side-chain DMP and DEP were degraded rapidly, while long-side-chain DBP and DEHP were degraded slowly.

Biodegradation of oil wastewater by free and immobilized Yarrowia lipolytica W29

The ability of Yarrowia lipolytica W29 immobilized by calcium alginate to degrade oil and chemical oxygen demand （COD） was examined. The degradation rules of oil and COD by immobilized cells with the cell density of 6.65 × 10^6 CFU/mL degraded 2000 mg/L oil and 2000 mg/L COD within 50 h at 30℃ （pH 7.0, 150 r/min）, similarly to those of free cells, and the degradation efficiencies of oil and COD by immobilized cells were above 80%, respectively. The factors affecting oil and COD degradation by immobilized cells were investigated, the results showed that immobilized cells had high thermostability compared to that of free cells, and substrate concentration significantly affected degrading ability of immobilized cells. Storage stability and reusability tests revealed that the oil degradation ability of immobilized cells was stable after storing at 4~C for 30 d and reuse for 12 times, respectively, the COD degradation rate of immobilized cells was also maintained 82% at the sixth cycle. These results suggested that immobilized Y lipolytica might be applicable to a wastewater treatment system for the removal of oil and COD.

Biodegradation of phenol by free and immobilized Acinetobacter sp.strain PD12

A new phenol-degrading bacterium with high biodegradation activity and high tolerance of phenol, strain PD 12, was isolated from the activated sludge of Tianjin Jizhuangzi Wastewater Treatment Facility in China. This strain was capable of removing 500 mg phenol/L in liquid minimal medium by 99.6% within 9 h and metabolizing phenol at concentrations up to 1100 mg/L. DNA sequencing and homologous analysis of 16S rRNA gene identified PD12 to be an Acinetobacter sp. Polyvinyl alcohol （PVA） was used as a gel matrix to immobilize Acinetobacter sp. strain PDI2 by repeated freezing and thawing. The factors affecting phenol degradation of immobilized cells were investigated, and the results showed that the immobilized cells could tolerate a high phenol level and protected the bacteria against changes in temperature and pH. Storage stability and reusability tests revealed that the phenol degradation functions of immobilized cells were stable after reuse for 50 times or storing at 4℃ for 50 d. These results indicate that immobilized Acinetobacter sp. strain PD 12 possesses a good application potential in the treatment of phenol-containing wastewater.

Nitrobenzene biodegradation ability of microbial communities in water and sediments along the Songhua River after a nitrobenzene pollution event

More than 100 t of nitrobenzene (NB) and related compounds were discharged into the Songhua River,the fourth longest river in China,because of the world-shaking explosion of an aniline production factory located in Jilin City on November 13,2005.As one of the efforts to predict the fate of residual NB in the river,NB biodegradation abilities by microbes in the water and sediments from different river sections were evaluated systematically.The results indicated that microbial communities from any section of ...

Biodegradation of methyl parathion by Acinetobacter radioresistens USTB-04

Biodegradation of methyl parathion （MP）, a widely used organophosphorus pesticide, was investigated using a newly isolated bacterium strain Acinetobacter radioresistens USTB-04. MP at an initial concentration of 1200 mg/L could be totally biodegraded by A. radioresistens USTB-04 as the sole carbon source less than 4 d in the presence of phosphate and urea as phosphorus and nitrogen sources, respectively. Biodegradation of MP was also achieved using cell-free extract of A. radioresistens USTB-04. MP at an initial concentration of 130 mg/L was completely biodegraded in 2 h in the presence of cell-free extract with a protein concentration of 148.0 mg/L, which was increased with the increase of pH from 5.0 to 8.0. Contrary to published reports, no intermediate or final degradation metabolites of MP could be observed. Thus we suggest that the cleavage of C-C bond on the benzene ring other than P-O bond may be the biodegradation pathway of MP by A. radioresistens USTB-04.

Optimizing aerobic biodegradation of dichloromethane using response surface methodology

Response surface methodology （RSM） was employed to evaluate the optimum aerobic biodegradation of dichloromethane （DCM） in pure culture. The parameters investigated include the initial DCM concentration, glucose as an inducer and hydrogen peroxide as terminal electron acceptor （TEA）. Maximum aerobic biodegradation efficiency was predicted to occur when the initial DCM concentration was 380 mg/L, glucose 13.72 mg/L, and H202 115 mg/L. Under these conditions the aerobic biodegradation rate reached up to 93.18%, which was significantly higher than that obtained under original conditions. Without addition of glucose degradation efficiencies were ≤ 80% at DCM concentrations ≤ 326 mg/L. When concentrations of DCM were more than 480 rag/L, the addition of hydrogen peroxide did not help to significantly increase DCM degradation efficiency. When DCM concentrations increased from 240 to 480 rag/L, the overall DCM degradation efficiency decreased from 91% to 60% in the presence of HaO2 for 120 mg/L.

Biodegradation of acetanilide herbicides acetochlor and butachlor in soil

The biodegradation of two acetanilide herbicides, acetochlor and butachlor in soil after other environmental organic matters addition were measured during 35 days laboratory incubations. The herbicides were applied to soil alone, soil SDBS (sodium dodecylbenzene sulfonate) mixtures and soil HA (humic acid) mixtures. Herbicide biodegradation kinetics were compared in the different treatment. Biodegradation products of herbicides in soil alone samples were identified by GC/MS at the end of incubation. Addition of SDBS and HA to soil decreased acetochlor biodegradation, but increased butachlor biodegradation. The biodegradation half life of acetochlor and butachlor in soil alone, soil SDBS mixtures and soil HA mixtures were 4.6d, 6.1d and 5.4d and 5.3d, 4.9d and 5.3d respectively. The biodegradation products were hydroxyacetochlor and 2 methyl 6 ethylaniline for acetochlor, and hydroxybutachlor and 2,6 diethylaniline for butachlor.

Impacts of heavy metals on 1,2-dichloroethane biodegradation in co-contaminated soil

1,2-Dichloroethane （DCA）, a potential mutagen and carcinogen, is commonly introduced into the environment through its industrial and agricultural use. In this study, the impact of lead and mercury on DCA degradation in soil was investigated, owing to the complex co-contamination problem frequently encountered in most sites. 1,2-Dichloroethane was degraded readily in both contaminated loam and clay soils with the degradation rate constants ranging between 0.370-0.536 week-1 and 0.309-0.417 week-1, respectively. The presence of heavy metals have a negative impact on DCA degradation in both soil types, resulting in up to 24.11% reduction in DCA degradation within one week. Both biostimulation and treatment additives increased DCA degradation, with the best degradation observed upon addition of glucose and a combination of diphosphate salt and sodium chloride, leading to about 17.91% and 43.50% increase in DCA degradation, respectively. The results have promising potential for effective remediation of soils co-contaminated with chlorinated organics and heavy metals. However, the best bioremediation strategy will depend on the soil types, microbial population present in the soil matrices, nutrients availability and metal forms.

Biodegradation of Gaseous Chlorobenzene by White-rot Fungus Phanerochaete chrysosporium

Objective To evaluate the effect of white rot fungus Phanerochaete chrysosporium on removal of gaseous chlorobenzene. Methods Fungal mycelium mixed with a liquid medium was placed into airtight bottles. A certain amount of chlorobenzene was injected into the headspace of the bottles under different conditions. At a certain interval, the concentrations in the headspace were analyzed to evaluate the degradation of chlorobenzene by P. chrysosporium. Results The degradation effects of P. chrysosporium on chlorobenzene under different conditions were investigated. The difference in the optimum temperature for the growth of the fungi and chlorobenzene degradation was observed. The data indicated that a lower temperature （28℃） would promote the degradation of chlorobenzene than the optimum temperature for the growth of the fungi （37℃）. A low nitrogen source concentration （30 mg N/L） had a better effect on degrading chlorobenzene than a high nitrogen source concentration （higher than 100 mg N/L）. A high initial concentration （over 1100 mg/m3） of chlorobenzene showed an inhibiting effect on degradation by P chrysosporium. A maximum removal efficiency of 95% was achieved at the initial concentration of 550 mg/m3. Conclusion P. chrysosporium has a rather good ability to remove gaseous chlorobeuzene. A low nitrogen source concentration and a low temperature promote the removal of chlorobenzene by P. chrysosporium. However, a high initial chlorobenzene concentration can inhibit chlorobenzene degradation.

Influence of nonionic surfactant on the solubilization and biodegradation of phenanthrene

Phenanthrene was solubilized in two different nonionic surfactants, Tween80 and Triton X-100. The bioavailability of phenanthrene to the bacteria isolated from the petroleum contaminated soils was studied based on the rotary flasks experiments. The results showed that the concentration of nonionic surfactants above the critical micelle concentration(CMC) can increase the solubility of phenanthrene in water and were innoxious to the phenanthrene-degrading bacteria; phenanthrene solubilized in the micelles of Tween80 was bioavailable and biodegradable. The research demonstrated the potential of surfactant-enhanced bioremediation of soils contaminated by hydrophobic organic compounds(HOCs).

Comparison of Di-n-methyl Phthalate Biodegradation by Free and Immobilized Microbial Cells

To compare the biodegradation of di-n-methyl pathalate by free and immobilized microbial cells. Methods The enrichment and isolation technique was used to isolate the microorganism. The PAV-entrapment method was utilized to immobilize the microorganisms. The scanning electron microscophy (SEM) was used to observe the growth and distribution of microbial cells immobilized inside the PVA bead gels. The GC/MS method was used to identify the main intermediates of DMP degradation. Results The microbial cells could grow quite well in PVA gel. The metabolic pathway did not change before and after immobilization of the microbial cells. The degradation rate of immobilized cells was higher than that of free cells. Conclusion The immobilized microbial cells possess advantages than free cells when applied to the biodegradation of toxic organic pollutants.

Biodegradation of mixture of VOC's in a biofilter

Volatile organic compounds(VOC's) in air have become major concern in recent years. Biodegradation of a mixture of ethanol and methanol vapor was evaluated in a laboratory biofilter with a bed of compost and polystyrene particles using an acclimated mixed culture. The continuous performance of the biofilter was studied with different proportion of ethanol and methanol at different initial concentration and flow rates. The result showed significant removal for both ethanol and methanol, which were composition dependent. The presence of either compound in the mixture inhibited the biodegradation of the other.

Biodegradation of phenol and m-cresol by mutated Candida tropicalis

The phenol and m-cresol biodegradations were studied using the mutant strain CTM 2 obtained by the He-Ne laser irradiation on wild-type Candida tropicalis. The results showed that C. tropicalis exhibited the increased capacity of phenolic compounds degradation after laser irradiation. It could degrade 2600 mg/L phenol and 300 mg/L m-cresol by 5% inoculum concentration, respectively. In the dual-substrate biodegradation system, 0-500 mg/L phenol could accelerate m-cresol biodegradation, and 300 mg/L m-cresol could be completely utilized within 46 hr at the presence of 350 mg/L phenol. Besides, the maximum biodegradation of m-cresol could reach 350 mg/L with 80 mg/L phenol within 61 hr. Obviously, phenol, as a growth substrate, could promote CTM 2 to degrade m-cresol, and was always preferentially utilized as carbon source. Comparatively, low-concentration m-cresol could result in a great inhibition on phenol degradation. In addition, the kinetic behaviors of cell growth and substrate biodegradation were described by kinetic model proposed in our laboratory.

Alleviation of mycotoxin biodegradation agent on zearalenone and deoxynivalenol toxicosis in immature gilts

Background: The current study was carried out to evaluate the effects of mycotoxin biodegradation agent(MBA, composed of Bacillus subtilis ANSB01 G and Devosia sp. ANSB714) on relieving zearalenone(ZEA) and deoxynivalenol(DON) toxicosis in immature gilts.Methods: A total of forty pre-pubertal female gilts(61.42 ± 1.18 kg) were randomly allocated to four diet treatments: CO(positive control); MO(negative control, ZEA 596.86 μg/kg feed and DON 796 μg/kg feed);COA(CO + 2 g MBA/kg feed); MOA(MO + 2 g MBA/kg feed). Each treatment contained 10 replicates with 1 gilt per replicate. Gilts were housed in an environmentally controlled room with the partially slatted floor.Results: During the entire experimental period of 28 d, average daily gain(ADG) and average daily feed intake(ADFI)of gilts in MO group was significantly reduced compared with those in CO group. The vulva size of gilts was significantly higher in MO group than CO group. In addition, significant increases in the plasma levels of Ig A,Ig G, IL-8, IL-10 and PRL were determined in MO group compared with that in CO group. ZEA and DON in the diet upregulated apoptotic caspase-3 in ovaries and uteri, along with down-regulated the anti-apoptotic protein Bcl-2 in ovaries. The supplementation of MBA into diets co-contaminated with ZEA and DON significantly increased ADG, decreased the vulva sizes, reduced the levels of Ig G, IL-8 and PRL in plasma, and regulated apoptosis in ovaries and uteri of gilts.Conclusions: The present results indicated that feeding diet contaminated with ZEA and DON simultaneously(596.86 μg/kg + 796 μg/kg) had detrimental effects on growth performance, plasma immune function and reproductive status of gilts. And MBA could reduce the negative impacts of these two toxins, believed as a promising feed additive for mitigating toxicosis of ZEA and DON at low levels in gilts.