Biodegradation

Batch experiments were carried out to investigate the stoichiometry and kinetics of microbial degradation of toluene under denitrifying conditions. The inoculum originated from a mixture of sludges from sewage treatment plants with alternating nitrification and denitrification. The culture was able to degrade toluene under anaerobic conditions in the presence of nitrate, nitrite, nitric oxide, or nitrous oxide. No degradation occurred in the absence of Noxides. The culture was also able to use oxygen, but ferric iron could not be used as an electron acceptor. In experiments with 14C-labeled toluene, 34% 4-8% of the carbon was incorporated into the biomass, while 53% 4-10% was recovered as t4CO2, and 6% + 2% remained in the medium as nonvolatile water soluble products. The average consumption of nitrate in experiments, where all the reduced nitrate was recovered as nitrite, was 1.3 :t: 0.2 mg of nitrate-N per mg of toluene. This nitrate reduction accounted for 70% of the electrons donated during the oxidation of toluene. When nitrate was reduced to nitrogen gas, the consumption was 0.7 4-0.2 nag per mg of toluene, accounting for 97% of the donated electrons. Since the ammonia concentration decreased during degradation, dissimilatory reduction of nitrate to ammonia was not the reductive process. The degradation of toluene was modelled by classical Monod kinetics. The maximum specific rate of degradation, k, was estimated to be 0.71 mg toluene per mg of protein per hour, and the Monod saturation constant, Ks, to be 0.2 mg toluene/1. The maximum specific growth rate,/~,~ax, was estimated to be 0.1 per hour, and the yield coefficient, Y, was 0.14 mg protein per mg toluene.

The kinetics of abiotic oxidation in the dark and the kinetics of biological mineralization in soil and in a compost environment of thermally oxidized LDPE were studied. It was demonstrated that different activation energies are obtained for the thermal oxidation, depending on the composition of the materials. Significantly higher levels of biodegradability have been obtained in a soil environment at 23 C compared with the compost environment at 58 C. After two years of mineralization, 91% conversion to carbon dioxide was obtained in the soil test, compared with 43% in the compost test. The differences between fungal, archaeal and bacterial community structures in soil and compost after 607 days of biodegradability assay were mapped out. It was found that the most dominant bacterial and fungal terminal restriction fragments (TRFs) in the compost containing the test material are significantly different from the TRFs in the other environments.

Structural information on soil organic matter (SOM) at the molecular level can be obtained on diverse structural units that are amenable to degradation techniques. Chemolytic techniques in combination with colorimetric analyses or GC MS are used to determine amino acids (proteins), sugars (polysaccharides), lipids, or aromatic oxidation products from lignin or charred organic matter. Microbial markers (amino sugars, muramic acid) are analyzed after hydrolysis and gas chromatographic separation. Macromolecular structures can also be subjected to thermochemolytic degradation or pyrolysis and subsequent analysis of the fragments by GC MS. Alternative techniques for the examination of organic matter in heterogeneous macromolecular mixtures are non-destructive spectroscopic methods, such as nuclear magnetic resonance (NMR) spectroscopy. Although this technique can give good results concerning the gross chemical composition, speci®c compounds are hardly identi®ed. The combination of spectroscopic techniques with thermolytic and chemolytic methods will add substantially to the understanding of the nature of refractory soil organic matter. Physical fractionation prior to analysis provides a means to dierentiate between distinct SOM pools that can be further characterized by the methods described above. Studies on SOM structural characteristics have focused mainly on the A horizons of soils under agriculture and litter biodegradation in forest soils and need to be extended to a wider variety of soil types and the subsoil. #

Plastics are polymers of higher molecular mass of synthetic or semi-synthetic organic solids used as inputs for industries. Over the
last few years, the need for biodegradable plastics has led to extended significance due to the extreme use of plastics and increasing
pressure being positioned on to be had capacities for plastic waste disposal. Lack of degradability and the closing of landfill sites
as well as growing water and land pollutant problems have caused the situation about plastics. Plastics are causing great difficulty
in environmental problems and consequently, this desires manufacturers to synthesize materials that do not have an impact on the
environment. The use of microorganisms in the surrounding to metabolize the molecular shape of plastic materials to produce
an inert humus-like material and this is much less dangerous to the surroundings, furthermore, expertise their interaction and
the biochemical adjustments they undergo are tremendously essential. In addition, the use of bio-active compounds coated with
swelling materials ensures that once it is far mixed, with heat and moisture, they make bigger the plastics molecular structure and
permit the bio-lively compounds to metabolize and neutralize the plastic. Thus, this overview article is revised to inspire and make
an impact on the importance of microorganisms on biodegradation plastic substances.

The extracellular and intracellular metabolites formed upon exposure of activated sludge microorganisms to a sublethal concentration of N-ethylmaleimide were monitored by liquid chromatography with ion trap mass spectrometry. The metabolite N-ethylsuccinimido-S-glutathione (m/z 433) was converted rapidly to N-(2-oxoethyl)-2,2-(propionylamino)propanamide (m/z 187) and N-ethylmaleamic acid (m/z 144).

HDPE Aspergillus tubingensis VRKPT1 Aspergillus flavus VRKPT2 Fourier transformed infra-red spectroscopy Scanning electron microscopy a b s t r a c t High density polyethylene (HDPE) is the most commonly found non-degradable solid waste among the polyethylene. In this present study, HDPE degrading various fungal strains were isolated from the polyethylene waste dumped marine coastal area and screened under in vitro condition. Based on weight loss and FT-IR Spectrophotometric analysis, two fungal strains designated as VRKPT1 and VRKPT2 were found to be efficient in HDPE degradation. Through the sequence analysis of ITS region homology, the isolated fungi were identified as Aspergillus tubingensis VRKPT1 and Aspergillus flavus VRKPT2. The biofilm formation observed under epifluorescent microscope had shown the viability of fungal strains even after one month of incubation. The biodegradation of HDPE film nature was further investigated through SEM analysis. HDPE poses severe environmental threats and hence the ability of fungal isolates was proved to utilize virgin polyethylene as the carbon source without any pre-treatment and pro-oxidant additives.

A newly developed and validated constitutive model that accounts for primary compression and timedependent mechanical creep and biodegradation is used for parametric study to investigate the effects of model parameters on the predicted settlement of municipal solid waste (MSW) with time. The model enables the prediction of stress strain response and yield surfaces for three components of settlement: primary compression, mechanical creep, and biodegradation. The MSW parameters investigated include compression index, coefficient of earth pressure at-rest, overconsolidation ratio, and biodegradation parameters of MSW. A comparison of the predicted settlements for typical MSW landfill conditions showed significant differences in time-settlement response depending on the selected model input parameters. The effect of lift thickness of MSW on predicted settlement is also investigated. Overall, the study shows that the variation in the model parameters can lead to significantly different results; therefore, the model parameter values should be carefully selected to predict landfill settlements accurately. It is shown that the proposed model captures the time settlement response which is in general agreement with the results obtained from the other two reported models having similar features.

In this paper the production of laccase and the decolouration of the recalcitrant diazo dye Reactive Black 5 (RB5) by the white-rot fungus Trametes pubescens immobilised on stainless steel sponges in a fixed-bed reactor were studied. Laccase production was increased by 10-fold in the presence of RB5 and reached a maximum value of 1025 U/l. Enhanced laccase production in the presence of RB5 in this fungus is an added advantage during biodegradation of RB5-containing effluents. The decolouration of RB5 was due to two processes: dye adsorption onto the fungal mycelium and dye degradation by the laccase enzymes produced by the fungus. RB5 decolouration was performed during four successive batches obtaining high decolouration percentages (74%, 43% and 52% in 24 h for the first, third and four batch, respectively) without addition of redox mediators. Also, the in vitro decolouration of RB5 by the concentrated culture extract, containing mainly laccase, produced in the above bioreactor was studied. The decolouration percentages obtained were considerably lower (around 20% in 24 h) than that attained with the whole culture.

Bioremediation is a possible mechanism for clean-up of hydrocarbon-contaminated soils in the Antarctic. Microbes indigenous to the Antarctic are required that degrade the hydrocarbon contaminants found in the soil, and that are able to survive and maintain activity under in situ conditions. Alkane- degrading bacteria previously isolated from oil-contaminated soil from around Scott Base, Antarctica, grew on a number of n-alkanes from hexane (C6) through to eicosane (C20) and the branched alkane pristane. Mineralization of 14C-dodecane was demonstrated with four strains. Representative isolates were identified as Rhodococcus species using 16S rDNA sequence analysis. Rhodococcus spp. strains 5/14 and 7/1 grew at −2°C but numbers of viable cells declined when incubated at 37°C. Both strains appear to have the major cold-shock gene cspA. Partial nucleotide sequence analyses of the PCR-amplified cspA open reading frame from Rhodococcus spp. strains 5/14 and 7/1 were approximately 60% identical to cspA from Escherichia coli.

The Main objective of the present study was to develop polysaccharide based biopolymer films with similar properties comparable to synthetic polymer films using waste materials of plant origin ,especially by the utilization of starch and pectin from plant source namely Mangifera indica (Mango kernel starch) and Cyphomandra betacea (Tree tomato pectin) . To overcome the problems due to usage of plastics, to conserve non-renewable resources like petroleum, natural gas and coal, to maintain ecological balance and to reduce pollution it is the need of the hour to develop ecofriendly biodegradable plastics that are made from renewable resources. An effort had been taken to develop a polysaccharide based polymer film and to study the filmogenicity and biodegradability of mango kernel starch-polyvinyl alcohol cross linked film. Mango kernel starch was isolated and evaluated for the physiochemical property and biodegradability of the prepared polysaccharide based film. The isolated starch showed a good physicochemical property and film forming property with polyvinyl alcohol and pectin. The developed polysaccharide based polymer film can be used as a substitute for synthetic polymer in pharmaceutical industry.

This study investigated the removal efficiency and mechanisms of water contaminants (mainly N-nitrosamines) during municipal wastewater reclamation by a membrane bioreactor (MBR) and nanofiltration (NF) hybrid system. The removal of bulk water contaminants was governed by the microbial activities in the MBR and molecular weight cut-off (MWCO) of the NF membranes. The removal of N-nitrosamines by the MBR was primarily attributed to biodegradation by aerobic bacteria, which can be determined by the reactivity of the amine functional groups with the catabolic enzymes (removal efficiency=45-84%). Adsorption and formation of membrane fouling can enhance the removal of N-nitrosamines by the NF membranes. However, size-exclusion is found to play a major role in the removal of N-nitrosamines by the NF membranes since the removal efficiencies of N-nitrosamines varied significantly depending on molecular weight of the N-nitrosamines and MWCO of the NF membranes (removal efficiency: NE90>NE...

A cross-linking reagent is required to improve mechanical strength and degradation properties of biopolymers for tissue engineering. To find the optimal preparative method, we prepared diverse genipin-cross-linked chitosan/collagen scaffolds using different genipin concentrations and various cross-linking temperatures and cross-linking times. The compressive strength increased with the increasing of genipin concentration from 0.1 to 1.0%, but when concentration exceeded 1.0%, the compressive strength decreased. Similarly, the compressive strength increased with the increasing of temperature from 4 to 20°C, but when temperature reached 37°C, the compressive strength decreased. Showing a different trend from the above two factors, the effect of cross-linking time on the compressive strength had a single increasing tendency. The other results also demonstrated that the pore size, degradation rate and swelling ratio changed significantly with different cross-linking conditions. Based on our study, 1.0% genipin concentration, 20°C cross-linking temperature and longer cross-linking time are recommended. Long Bi and Zheng Cao contributed equally to this work.

Petroleum hydrocarbons are widespread environmental pollutants. Although biodegradation of petroleum hydrocarbons has been the subject of numerous investigations, information on their toxicity to microorganisms in soil is limited, with virtually no work conducted on soil algae. We carried out a screening experiment for total petroleum hydrocarbons (TPH) and their toxicity to soil algal populations, microbial biomass, and soil enzymes (dehydrogenase and urease) in a long-term TPH-polluted site with reference to an adjacent unpolluted site. Microbial biomass, soil enzyme activity, and microalgae declined in medium to high-level (5,200-21,430 mg kg Ϫ1 soil) TPH-polluted soils, whereas low-level (Ͻ2,120 mg kg Ϫ1 soil) pollution stimulated the algal populations and showed no effect on microbial biomass and enzymes. However, inhibition of all the tested parameters was more severe in soil considered to have medium-level pollution than in soils that were highly polluted. This result could not be explained by chemical analysis alone. Of particular interest was an observed shift in the species composition of algae in polluted soils with elimination of sensitive species in the medium to high polluted soils. Also, an algal growth inhibition test carried out using aqueous eluates prepared from polluted soils supported these results. Given the sensitivity of algae to synthetic pollutants, alteration in the algal species composition can serve as a useful bioindicator of pollution. The results of this experiment suggest that chemical analysis alone is not adequate for toxicological estimations and should be used in conjunction with bioassays. Furthermore, changes in species composition of algae proved to be more sensitive than microbial biomass and soil enzyme activity measurements. Enormous quantities of petroleum and its products are produced annually, refined, and transported on land and sea across the world. Consequently, risks and concern over petroleum hydro

A bacterial strain 5HP capable of degrading and utilizing 5-hydroxypicolinic acid as the sole source of carbon and energy was isolated from soil. In addition, the isolate 5HP could also utilize 3-hydroxypyridine and 3-cyanopyridine as well as nicotinic, benzoic and p-hydroxybenzoic acids for growth in the basic salt media. On the basis of 16S rRNA gene sequence analysis, the isolate 5HP was shown to belong to the genus Pusillimonas. Both the bioconversion analysis using resting cells and the enzymatic assay showed that the degradation of 5-hydroxypicolinic acid, 3-hydroxypyridine and nicotinic acid was inducible and proceeded via formation of the same metabolite, 2,5-dihydroxypyridine. The activity of a novel enzyme, 5-hydroxypicolinate 2-monooxygenase, was detected in the cell-free extracts prepared from 5-hydroxypicolinate-grown cells. The enzyme was partially purified and was shown to catalyze the oxidative decarboxylation of 5-hydroxypicolinate to 2,5-dihydroxypyridine. The activity of 5-hydroxypicolinate 2-monooxygenase was dependent on O 2 , NADH and FAD.

Aims:  The presented study was aimed to reveal transcriptional regulation of genes involved in SDS degradation (sdsA and sdsB) in Pseudomonas sp. ATCC19151. In addition, the ability of Pseudomonas sp. ATCC19151 to degrade anionic surfactants present in commercial detergent and septic tank drain was analysed.Methods and Results:  Strain ATCC19151, at 30°C, degrades all SDS present in the liquid medium (up to 4% w/v of SDS) within 48 h. ATCC19151 grows in the presence up to 15% (v/v) ‘Fairy’ commercial detergent and mineralizes 35% of present anionic surfactants. Analysis of the sdsA (PsdsA) and divergent sdsB (PsdsB) gene promoter activities revealed that SdsB acts as a positive regulator of sdsA and sdsB transcription. PsdsA and PsdsB activities rose significantly in the presence of the SDS, indicating inducibility of sdsA and sdsB transcription. DNA-binding assay indicated that SdsB directly regulates the transcription of sdsA and sdsB genes. Strain ATCC19151 grew in a sterile septic tank drain and on commercial detergent as sole source of carbon.Conclusions:  SdsA enables Pseudomonas sp. ATCC19151 to utilize SDS as a sole carbon source. SdsB is positive transcriptional regulator of sdsA and sdsB genes.Significance and Impact of the Study:  Ability of ATCC19151 to degrade anionic surfactants makes Pseudomonas sp. ATCC19151 a good candidate for bioremediation.

Fluorene degradation using immobilized Pleurotus ostreatus on various supports including polystyrene foam, Amberlite XAD-7, Amberlite XAD-2000, pumice particles and sand has been reported. These supports have yielded positive results with regard to performing metabolic functions, but the drawback of synthetic resins is that they are not eco-friendly. If natural supports could be used for cell immobilization for the degradation of fluorene, they would be both eco-friendly and perform metabolic functions. Therefore, This study attempts to design an immobilized P. ostreatus using pumice as a support specifically for the application of fluorene biodegradation in batch shaking systems. Laccase and MnP enzyme activities were monitored in these systems. The maximum fluorene degradation level was 89.16%. Batch degradation of fluorene in a packed bed reactor was also studied. The maximum fluorene degradation level was found to be 82.46%. Additionally, two different, synthetically concocted wastewater samples containing fluorene were studied in a recycled packed bed reactor in repeated mode. At the end of biodegradation process, the metabolites of the fluorene biodegradation produced by immobilized P. ostreatus were analyzed via GC-MS and FT-IR. It was concluded that the biotransformation of fluorene by immobilized P. ostreatus was achieved.

Biological upgrading of wheat straw by the white-rot fungi Phanerochaete chrysosporium, Pleurotus eryngii, Phlebia radiata, and Ceriporiopsis subvermispora was monitored during 60-day solid-state fermentation. Analysis of straw included determination of weight loss and lignin content, color analysis, and infrared spectroscopy, whereas the studies on the water-soluble fractions were carried out by infrared spectroscopy, elementary analyses and quantification of the total phenols and reducing sugars. The most selective degradation of lignin was produced by P. eryngii and especially by C. subvermispora, the former species releasing the greatest amount of colored water-soluble products, whereas an increase in straw brightness was caused by C. subvermispora. In general, the composition of the water-soluble fraction correlated with the extent of straw transformation. The initial fermentation stage (0-15 days) was characterized by the accumulation of water-soluble products from lignin degradation and fungal metabolism, the concentration of which tended to stabilize in the second stage (16-60 days). The degree of delignification at the second stage tended to coincide with the decrease of the water-soluble nitrogen.

2-Methylisoborneol (MIB), a metabolite of blue-green algae, has been implicated in causing unpalatable drinking water throughout the world. Current non-biological water treatment technologies are ineffective in removing MIB from potable water or are cost-prohibitive, and biological applications may address these problems. We have isolated and characterized a bacterium derived from lake water and capable of aerobically degrading MIB. Light microscopy and transmission electron microscopy revealed that this strain is a spore-forming, flagellated bacterium that is bacilloid in shape, and 16S rRNA phylogenetic analysis determined that it is most closely related to Bacillus fusiformis and Bacillus sphaericus, both members of the Bacillus sphaericus senso lato taxon. While the growth and oxidation potential of this strain was shown to be affected beyond certain MIB concentrations in the mg/l range, it was capable of depleting MIB at mg/l and ng/l concentrations and of removing MIB to concentrations yielding no observed odor.

Multiple bacterial strains with CBA metabolic properties were isolated using a simple selective strategy. Phylogenetic analysis of the 16S rRNA gene sequences grouped them into two main clusters consisting of four bacterial phyla and belonging to 17 genera. Whereas growth was more frequent with 2-CBA ($68%), 50% grew on 4-CBA and $7% utilized 3-CBA. One third of the strains exhibited 2,4-dichlorobenzoic acid (2,4-diCBA) catabolic function and were mainly representatives of a-, b-and c-Proteobacteria. In batch experiments, growth was concomitant with substrate disappearance and near-stoichiometric release of chloride. Doubling times for 2,4-diCBA degradation doubled those determined for mono-substituted CBAs. Out of the six 2,4-diCBA degraders submitted for enzyme assays, significant induction of catechol 1,2-dioxygenase types I and II activities in cell-free extracts were found in four while protocatechuate 3,4-dioxygenase activity was detected in the remaining two. Activities in CBA-grown cells were 20 orders-of-magnitude higher than those grown on benzoic acid.

A small fraction of the naphtha diluent used for oil sands processing escapes with tailings and supports methane (CH 4 ) biogenesis in large anaerobic settling basins such as Mildred Lake Settling Basin (MLSB) in northern Alberta, Canada. Based on the rate of naphtha metabolism in tailings incubated in laboratory microcosms, a kinetic model comprising lag phase, rate of hydrocarbon metabolism and conversion to CH 4 was developed to predict CH 4 biogenesis and flux from MLSB. Zero-and first-order kinetic models, respectively predicted generation of 5.4 and 5.1 mmol CH 4 in naphtha-amended microcosms compared to 5.3 (±0.2) mmol CH 4 measured in microcosms during 46 weeks of incubation. These kinetic models also predicted well the CH 4 produced by tailings amended with either naphtha-range n-alkanes or BTEX compounds at concentrations similar to those expected in MLSB. Considering 25% of MLSB's 200 million m 3 tailings volume to be methanogenic, the zero-and first-order kinetic models applied over a wide range of naphtha concentrations (0.01-1.0 wt%) predicted production of 8.9-400 million l CH 4 day À1 from MLSB, which exceeds the estimated production of 3-43 million l CH 4 day À1 . This discrepancy may result from heterogeneity and density of the tailings, presence of nutrients in the microcosms, and/or overestimation of the readily biodegradable fraction of the naphtha in MLSB tailings.

An innovative bioprocess method, Systematic Environmental Molecular Bioremediation Technology (SEMBT) that combines bioaugmentation and biostimulation with a molecular monitoring microarray biochip, was developed as an integrated bioremediation technology to treat S-and ...

Pentachlorophenol (PCP) was studied as a model recalcitrant compound for a sequential chemical oxidation and biodegradation treatment, in a continuous laboratory-scale system that combined a Fenton's chemical reactor and a packed-bed bioreactor.

In this work, feasibility of using chemical pretreatment to improve the anaerobic biological degradation of industrial effluents containing high concentrations of phenolic compounds was investigated. For this purpose, chemical pretreatment of the wastewater generated from olive oil production process, namely olive mill effluent (OME), was conducted by means of acid cracking followed by coagulation-flocculation process using one of the coagulating agents such as Al 2 SO 4 , FeSO 4 and FeCl 3, respectively. Biochemical methane potential (BMP) assay was carried out for both crude OME and chemically pretreated OME samples in order to monitor and comparatively evaluate any increase in biogas production as the indicator of improvement in anaerobic biological degradation after chemical pretreatment. The experimental results obtained in this work suggest that pretreatment significantly enhances the biodegradability of OME which was much lower if it was digested alone (without pretreatment). Over 80% increase in biogas production was obtained when digesting OME after chemical pretreatment. It was concluded that among the alternative chemicals, Al 2 SO 4 resulted in highest biogas production from OME, thereby the best results for the enhancement of anaerobic biodegradability of OME were also achieved. It was demonstrated that the biodegradability of OME could be significantly enhanced by chemical pretreatment and therefore anaerobic degradation after a suitable pretreatment could be considered as a safe disposal method for OME.

Bitumens of the Alberta tar sands share a similar primary source rock, but exhibit varying levels of degradation. In the Peace River tar sands area, the wide range of API gravity and sulphur content in Lower Cretaceous reservoirs is investigated in terms of biodegradation processes, using detailed geochemical analyses, burial history modelling and charge/degrade modelling. Decreasing tar sand degradation to the west can be attributed to increasing reservoir temperatures which retard biodegradation. Gething oils west of the Peace River tar sands are derived from the same source, but are minimally degraded due to reservoir pasteurization at 80°C shortly after charging. Long charge times, reservoir filling and possibly compositional or very low temperature degradation retardation have limited biodegradation of the Alberta tar sands despite long oil residence times and low reservoir temperatures.

This review examines the enzymes of 4-chlorobenzoate to 4-hydroxybenzoate converting pathway found in certain soil bacteria. This pathway consists of three enzymes: 4-chlorobenzoate: Coenzyme A ligase, 4-chlorobenzoyl-Coenzyme A dehalogenase and 4-hydroxybenzoyl-Coenzyme A thioesterase. Recent progress made in the cloning and expression of the pathway genes from assorted bacterial strains is described. Gene order and sequence found among these strains are

This article focuses on the drying of native maize starch before compounding with poly(lactic acid) (PLA) and on the water absorption of injection-molded starch-filled PLA products. The mass loss of starch was examined while drying in a vented oven at various temperatures, and a proposal was made for complete drying. A temperature-dependent mathematical model was established to describe the moisture loss of native starch. The dried starch was mixed with PLA, compounded with a twin-screw extruder, and finally injection-molded into 80 3 80 mm 2 area, 2-mm-thick flat specimens. These specimens were placed into distilled water to analyze the water uptake and the change in mechanical properties and deformation caused by water uptake for 1 month. Another mathematical model was established to describe the water absorption of the specimens. With the proper drying of starch and PLA, a 30 wt% starch content PLA product was injection-molded with significantly higher tensile strength compared with literature data. POLYM. ENG. SCI.,

The combined remediation mechanisms of volatilization and biodegradation in the vadose zone were investigated for naphthalene remediation at a creosote-contaminated site where a poplar tree-based phytoremediation system has been installed. Concurrent field and laboratory experiments were conducted to study the transport and biodegradation of naphthalene in the vadose zone. Soil gas sampling showed that more than 90% of the naphthalene vapors were biodegraded aerobically within 5-10 cm above the water table during the summer months. Peak naphthalene soil gas concentrations were observed in the late summer, corresponding with peak naphthalene aqueous concentrations and the minimum saturated zone thickness. An analytical solution was developed for vapor transport where the diffusion coefficient and firstorder biodegradation rate vary vertically in two discrete zones. First-order aerobic biodegradation rates in laboratory columns using unsaturated site soil ranged from 5 to 28 days-1 with a mean rate of 11 days-1. The observed naphthalene mass flux at the source (3.3-22 µg cm-2 d-1) was enhanced by aerobic biodegradation and was greater than the mean observed flux in the abiotic control column and the maximum theoretical mass flux by factors of 7 and 28, respectively.

The microbial activity within activated sludge floc is a key factor in the performance of the activated sludge process. In this study, the microenvironment of activated sludge flocs from two wastewater treatment plants (Mill Creek Wastewater Treatment Plant and Muddy Creek Wastewater Treatment Plant, with aeration tank influent CODs of 60-120 and 15-35 mg/L, respectively) were studied by using microelectrodes. Due to microbial oxygen utilization, the aerobic region in the activated sludge floc was limited to the surface layer (0.1-0.2mm) of the sludge aggregate at the Mill Creek plant. The presence of an anoxic zone inside the sludge floc under aerobic conditions was confirmed in this study. When the dissolved oxygen (DO) in the bulk liquid was higher than 4.0mg/L, the anoxic zone inside the activated sludge floc disappeared, which is helpful for biodegradation. At the Muddy Creek plant, with its lower wastewater pollutant concentrations, the redox potential and DO inside the sludge...

Eight new primer sets were designed for PCR detection of (i) mono-oxygenase and dioxygenase gene sequences involved in initial attack of bacterial aerobic BTEX degradation and of (ii) catechol 2,3-dioxygenase gene sequences responsible for metacleavage of the aromatic ring. The new primer sets allowed detection of the corresponding genotypes in soil with a detection limit of 10 3 -10 4 or 10 5 -10 6 gene copies g À 1 soil, assuming one copy of the gene per cell. The primer sets were used in PCR to assess the distribution of the catabolic genes in BTEX degrading bacterial strains and DNA extracts isolated from soils sampled from different locations and depths (vadose, capillary fringe and saturated zone) within a BTEX contaminated site. In both soil DNA and the isolates, tmoA-, xylM-and xylE1-like genes were the most frequently recovered BTEX catabolic genes. xylM and 0167-7012/$ -see front matter D xylE1 were only recovered from material from the contaminated samples while tmoA was detected in material from both the contaminated and non-contaminated samples. The isolates, mainly obtained from the contaminated locations, belonged to the Actinobacteria or Proteobacteria (mainly Pseudomonas). The ability to degrade benzene was the most common BTEX degradation phenotype among them and its distribution was largely congruent with the distribution of the tmoA-like genotype. The presence of tmoA and xylM genes in phylogenetically distant strains indicated the occurrence of horizontal transfer of BTEX catabolic genes in the aquifer. Overall, these results show spatial variation in the composition of the BTEX degradation genes and hence in the type of BTEX degradation activity and pathway, at the examined site. They indicate that bacteria carrying specific pathways and primarily carrying tmoA/xylM/xylE1 genotypes, are being selected upon BTEX contamination. D

The elite anaerobic fungal cultures Neocallimastix sp GR-1, Piromyces sp WNG-12 and Orpinomyces sp C-14 were isolated from wild blue bull and cattle respectively of grazing and browsing goat. Attempts were made to grow these cultures in normal media or using stress conditions by keeping them at lower or higher temperature than 39oc or using a complex media; Normal media produced maximum number of fungal zoospores after 120 hrs of incubation. The in- vitro dry matter, acid detergent fibre, neutral detergent fibre digestibility were studied using fresh zoospores; or those being kept at normal; lower or higher temperature than 39oC. Based on in vitro digestibility of DM, NDF and ADF of wheat straw and wheat straw based total mixed rations. The Neocallimastix sp GR-1was found better as compared to Piromyces sp WNG-12 and Orpinomyces sp C-14as this anaerobic fungi produced maximum numbers of zoospores and also proved to be best performing for its ability to degrade lignified feed material.

Oily sludge obtained from a refinery in India contained 10e11% oil associated with fine particulates. Along with Fe, Ca and Mg various toxic elements were associated with the sludge solids (Pb, Mn, Cu, Zn, As, Bi, Cd, Cr, Co, Ni and V). The oil contained 41e56% asphaltenes and the maltenes comprised of 49 ± 4%, 42 ± 2% and 4 ± 2%, aliphatic, aromatic and polar fractions, respectively. Biodegradation studies with the maltene fraction of oil provided as sole substrate revealed higher degradation by various 3-5 membered reconstituted consortia compared to pure bacterial strains and up to 42 ± 8% degradation could be achieved over 30 days. In contrast, over the same period up to 71.5 ± 2% oil degradation could be achieved using dried oily sludge (15% w/v) as sole substrate. Significant biodegradation observed in the un-inoculated controls indicated the presence of indigenous microorganisms in oily sludge. However, large variability in oil degradation was observed in the un-inoculated controls. Greater biodegradation of the maltene fraction led to significant enrichment of asphaltenes in residual oil associated with the sludge.

Modeling oil biodegradation is an important step in predicting the long term fate of oil on beaches. Unfortunately, existing models do not account mechanistically for environmental factors, such as pore water nutrient concentration, affecting oil biodegradation, rather in an empirical way. We present herein a numerical model, BIOB, to simulate the biodegradation of insoluble attached hydrocarbon. The model was used to simulate an experimental oil spill on a sand beach. The biodegradation kinetic parameters were estimated by fitting the model to the experimental data of alkanes and aromatics. It was found that parameter values are comparable to their counterparts for the biodegradation of dissolved organic matter. The biodegradation of aromatics was highly affected by the decay of aromatic biomass, probably due to its low growth rate. Numerical simulations revealed that the biodegradation rate increases by 3-4 folds when the nutrient concentration is increased from 0.2 to 2.0 mg N/L.

Abstract:
Lignin, the nature’s plastic is the major pollutant from paper-pulp mill effluent due to its intense unaesthetic
brown color, hydrophobicity and poor mechanical properties, tends to be a recalcitrant compound. Textile dyebased
industries release colored effluents due to presence of large amount of mixture of dyes which is also
hazardous. Microbial extracellular lignin peroxidase enzymes have a potential to degrade lignin and a wide
range of complex aromatic dyestuffs. From various environmental niches eleven isolates were screened for
lignolytic activity, out of which two bacterial isolates Pseudomonas aeruginosa and Serratia marcescens were
able to decolorize 44% to 49% of lignin. The studies on biobleaching of paper-pulp mill effluent gave 60% to 75%
color reduction and in case of textile dye- based effluent 50% to 58% decolourization was observed. The
heterogeneous combination of lignin peroxidases from mixed consortia gave 80% to 85% color reduction in
treatment of paper-pulp mill effluent and 70% to 75% decolourization in treatment of textile dye-based effluent
which is significantly high. This system of lignin peroxidase may be efficiently used in biobleaching and
biodegradation of effluents from respective industries.
Keywords: Lignin Peroxidase, Decolourization, Paper-pulp mill effluent, Textile dye-based effluent.

In search of the optimal way to reduce the hazards of environmental contamination by formaldehyde (FD) and methanol the use of unconventional yeasts is proposed as exemplified by the methylotrophic yeast Hansenula polymorpha. In a very simplified environment of a model wastewater solution, H. polymorpha cells were able to grow on, and metabolize formaldehyde and methanol, applied as sole carbon sources, at concentrations typical for wastewaters of the chemical industry. Several experimental conditions were tested for cell growth and biodegradation kinetics. It was found that the yeast culture inoculated at low cell density was able to grow on initial FD levels up to 400 mg/l and the biomass yield was dependent on both, the amount of total carbon added and the physiological state of the cells. When high density of preadapted cell culture was used, the methylotrophs were fully viable and able to degrade formaldehyde present at initial concentrations up to 700 mg/l. The maximum limiting FD consumption rate was determined as approx. 400 mg/l per hour. Methanol, at concentrations up to 2 %, was easily utilized and did not have a negative effect on cell growth and respiration. It is suggested that in real wastewaters the eukaryotic microorganisms-in contrast to bacteria-might reveal greater adaptation potential to toxic levels of formaldehyde as well as to other wastewater constituents.

The ability of Pleurotus eryngii, Pleurotus ostreatus, Pleurotus pulmonarius and Pleurotus sajor-caju to degrade the aromatic pollutants 2,4-dichorophenol (2,4-DCP) and benzo(a)pyrene [B(a)P] in liquid culture and microcosm (using wheat straw as growth substrate and sea sand as a xenobiotic carrier) was investigated by HPLC and 14 CO 2 release from labeled pollutants. We found that 100 mM 2,4-DCP was very quickly transformed by the four fungi, disappearing 24 h after its addition to the liquid cultures. However, a 2-week incubation period was required to transform 100 mM B(a)P up to 75% by P. eryngii and P. pulmonarius. Whereas the fungi were able to begin degradation of the two pollutants with high transformation rates, their complete degradation (mineralization) rates were very low. Mineralization of B(a)P in liquid cultures was only observed with P. eryngii and P. pulmonarius, although the four Pleurotus species studied were able to mineralize this compound in solid state fermentation (SSF). The ligninolytic enzymes laccase and versatile peroxidase (VP), together with aryl-alcohol oxidase (AAO) providing extracellular H 2 O 2 , were found in liquid cultures. Except AAO, these enzymes were also detected in SSF experiments. In order to investigate the role of ligninolytic enzymes in the process, their action on both pollutants (50 mM) was studied in vitro in the absence and presence of redox mediators. As observed with the fungal cultures, 2,4-DCP was oxidized faster than B(a)P by both laccase (60% transformation after 6 h) and VP (100% transformation after 1 h). Moreover, laccase oxidation was strongly increased (up to 90% transformation after 3 h), by the presence of the mediators 2,2 0 -azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) or 1hydroxybenzotriazole (HBT). In the case of B(a)P, the presence of ABTS or HBT was strictly required for oxidation by laccase (25% transformation after 8 h). Degradation of B(a)P was also observed in reactions with VP (40% transformation after 6 h). The results obtained suggest that Pleurotus species can be used in applications focused to the degradation of aromatic pollutants using wheat straw as a growth substrate, and provide the first evidence on the direct transformation of recalcitrant aromatic pollutants by VP. q

Biodiesel, as an alternative fuel, is gradually receiving more popularity for use in internal combustion engines. However questions continue to arise with regard to its compatibility with elastomeric materials. The present work aims to investigate the comparative degradation of physical properties for different elastomers [e.g. ethylene propylene diene monomer (EPDM), silicone rubber (SR), polychloroprene (CR), polytetrafluroethylene (PTFE) and nitrile rubber (NBR)] upon exposure to diesel and palm biodiesel. Static immersion tests in B0(diesel), B10 (10% biodiesel in diesel), B20, B50 and B100(biodiesel) were carried out at room temperature (25 °C) for 1000 h. Different physical properties like, changes in weight and volume, hardness and tensile strength were measured at every 250 h of immersion time. Compositional changes in biodiesel due to exposure of different elastomers were investigated by Gas chromatography mass spectroscopy (GCMS). The overall sequence of compatible elastomers in palm biodiesel is found to be PTFE > SR > NBR > EPDM > CR.

http://www.sciencedirect.com/science/article/pii/S0360544210007139

Polyurethanes (PU) are the sixth most produced plastics with around 18-million tons in 2016, but since they are not recyclable, they are burned or landfilled, generating damage to human health and ecosystems. To elucidate the mechanisms that landfill microbial communities perform to attack recalcitrant PU plastics, we studied the degradative activity of a mixed microbial culture, selected from a municipal landfill by its capability to grow in a water PU dispersion (WPUD) as the only carbon source, as a model for the BP8 landfill microbial community. The WPUD contains a polyether-polyurethane-acrylate (PE-PU-A) copolymer and xenobiotic additives (N-methylpyrrolidone, isopropanol and glycol ethers). To identify the changes that the BP8 microbial community culture generates to the WPUD additives and copolymer, we performed chemical and physical analyses of the biodegradation process during 25 days of cultivation. These analyses included Nuclear magnetic resonance, Fourier transform infrared spectroscopy, Thermogravimetry, Differential scanning calorimetry, Gel permeation chromatography, and Gas chromatography coupled to mass spectrometry techniques. Moreover, for revealing the BP8 community structure and its genetically encoded potential biodegradative capability we also performed a proximity ligation-based metagenomic analysis. The additives present in the WPUD were consumed early whereas the copolymer was cleaved throughout the 25-days of incubation. The analysis of the biodegradation process and the identified biodegradation products showed that BP8 cleaves esters, CC , and the recalcitrant aromatic urethanes and ether groups by hydrolytic and oxidative mechanisms, both in the soft and the hard segments of the copolymer. The proximity ligation-based metagenomic analysis allowed the reconstruction of five genomes, three of them from novel species. In the metagenome, Frontiers in Microbiology | www.frontiersin.org 1

Acrylic based resins are frequently used in daily dental practice. The most common use of the materials includes denture bases and denture liners, temporary crowns and orthodontic appliances. In the mouth, properties and functional efficiency of applied acrylic resins depend on internal factors related to the methods and conditions of polymerization and on external factors that are related to the environment in which the material is placed. Residual monomer, which is released as a result of interaction of both sets of factors is often associated with irritation, inflammatory and allergic reactions of oral mucosa. The aim of this paper is to review literature dealing with the conditions of polymerization and biodegradation of acrylic resins under certain conditions in the oral cavity and their impact on oral health (reviewed literature available on Medline database during the past two decades.) Conclusion: Methods and conditions of acrylate polymerization, on the one hand, and proper...

Constructed soil filter (CSF) also known as Soil Biotechnology (SBT) is a process for water renovation which makes use of formulated media with culture of soil macro-and microorganisms. CSF combines sedimentation, infiltration and biodegradation processes to remove oxidizable organics and inorganics of wastewater in a single facility. Operating experience shows hydraulic loading in the range of 0.05-0.25 m 3 /m 2 h and organic loading up to 200-680 g/m 2 d. The results show increase in dissolved oxygen levels, COD removal (from 352 mg/l to 20 mg/l); BOD removal (from 211 mg/l to 7.0 mg/l); suspended solids removal (from 293 mg/l to 16 mg/l); turbidity reduction (from 145 NTU to 5.3 NTU); iron (from 5 mg/l to 0.3 mg/l); arsenic (from 500 g/l to 10 g/l); total coliform and fecal coliform removal (from 145 × 10 5 to 55 CFU/100 mL and 150 × 10 8 to 110 CFU/100 mL respectively), with desired pathogen levels as per WHO standards, i.e. ≤10 3 CFU/100 mL. CSF reveals advantages such as low HRT (0.5-2.0 h), low energy requirement (0.04 kW h/m 3 ), no pre-treatment, high dissolved oxygen levels in the effluent, no biosludge production, no mechanical aeration and no odor, fish compatible water quality and evergreen ambience.

Inevitable consequences of the practice of solid waste disposal in landfills are gas and leachate generation due primarily to microbial decomposition, climatic conditions, refuse characteristics and landfilling operations. The migration of gas and leachate away from the landfill boundaries and their release into the surrounding environment present serious environmental concerns at both existing and new facilities. Besides potential health hazards, these concerns include, and are not limited to, fires and explosions, vegetation damage, unpleasant odors, landfill settlement, ground water pollution, air pollution and global warming. This paper presents an overview of gas and leachate formation mechanisms in landfills and their adverse environmental impacts, and describes control methods to eliminate or minimize these impacts.