Acetate Degradation Research Articles

Photochemical degradation study of polyvinyl acetate paints used in artworks by Py–GC/MS

Photochemical degradation of commercial polyvinyl acetate (PVAc) homopolymer and PVAc paints mixed with burnt umber, cobalt blue, cadmium red dark, nickel azo yellow and titanium white commonly used for artworks were studied by pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) and Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). Py–GC/MS with single-shot technique was used for the characterization of the thermal degradation of PVAc at different temperatures, while the double-shot technique of Py–GC/MS was used to reveal the differences in the specimens before and after UV ageing, including the changes of detectable amounts of deacetylation product – acetic acid and plasticizers such as diethyl phthalate (DEP). Furthermore, the relative concentration of the pyrolysis products of the paint samples could be measured and compared in the second step of the double-shot Py–GC/MS, which are highly dependent on the presence of pigments and the ageing status of PVAc paints.

Nitrate reduction by organotrophic Anammox bacteria in a nitritation/anammox granular sludge and a moving bed biofilm reactor

The effects of volatile fatty acids (VFAs) on nitrogen removal and microbial community structure in nitritation/anammox process were compared within a granular sludge reactor and a moving bed biofilm reactor. Nitrate productions in both systems were lower by 40–68% in comparison with expected nitrate production. Expected sludge production on VFAs was estimated to be 67–77% higher if heterotrophs were the main acetate degraders suggesting that Anammox bacteria used its organotrophic capability and successfully competed with general heterotrophs for organic carbon, which led to a reduced sludge production. FISH measurements showed a population consisting of mainly Anammox and AOB in both reactors and oxygen uptake rate (OUR) tests also confirmed that flocculent biomass consisted of a minor proportion of heterotrophs with a large proportion of AOBs. The dominant Anammox bacterium was Candidatus “Brocadia fulgida” with a minor fraction of Candidatus “Anammoxoglobus propionicus”, both known to be capable of oxidizing VFAs.

Effects of inorganic nanofillers on the thermal degradation and UV-absorbance properties of polyvinyl acetate

The effects of calcium carbonate (CaCO3) and calcium sulfate (CaSO4) nanoparticles on the thermal and UV-absorbing properties of polyvinyl acetate (PVAc) were analyzed in this study. Nanoparticles of CaCO3 and CaSO4 were synthesized by in situ deposition technique. The size and shape of nanoparticles were recognized by X-ray diffraction and scanning electron microscope (SEM) analyses which confirmed that the particle was having a diameter of 25–33 nm. In this technique, the surface modification of nanoparticles was done by non-ionic polymeric surfactant. PVAc/CaCO3 and PVAc/CaSO4 nanocomposites film samples with an average thickness of 30 µm and in the mass ratio of nanoparticles (0–4% (w/w)) were prepared by solution mixing technique. Chemical, structural, and elemental characterizations of nanocomposites were done by, fourier transform infrared, SEM, and energy dispersive X-ray spectroscopy analyses, respectively. Thermal properties of pure polymer and nanocomposites were characterized through differential scanning calorimetric, thermogravimetric, and differential thermogravimetry techniques. The glass transition temperature of nanocomposites increases with increase in content of nanoparticles. It may be due to the interaction between inorganic and organic components. The thermogravimetric analysis results indicate that the thermal degradation temperatures of nanocomposites were enhanced upon the addition of nanosized inorganic fillers. The thermal results show that PVAc/CaSO4 nanocomposites were more thermally stable than PVAc/CaCO3 nanocomposites. The addition of nanoparticles affects degradation mechanism and consequently improves thermal stability of PVAc. The reduction of polymer chain mobility and the tendency of nanoparticles to eliminate free radicals were the principal effects responsible for these enhancements. The ultraviolet–visible (UV–Vis) absorbance spectra of PVAc and its nanocomposites films show that the intensity of absorbance increases with increasing filling content, suggesting that nanocomposites films have greater UV-shielding property.

Role of calcium oxide in sludge granulation and methanogenesis for the treatment of palm oil mill effluent using UASB reactor

The granulation process in palm oil mill effluent using calcium oxide-cement kiln dust (CaO–CKD) provides an attractive and cost effective treatment option. In this study the efficiency of CaO–CKD at doses of 1.5–20 g/l was tested in batch experiments and found that 10 g of CaO/l caused the greatest degradation of VFA, butyrate and acetate. An upflow anaerobic sludge blanket (UASB) reactor was operated continuously at 35 °C for 150 days to investigate the effect of CaO–CKD on sludge granulation and methanogenesis during start-up. The treatment of POME emphasized the influence of varying organic loading rates (OLR). Up to 94.9% of COD was removed when the reactor was fed with the 15.5–65.5 g-COD g/l at an OLR of 4.5–12.5 kg-COD/m 3 d, suggesting the feasibility of using CaO in an UASB process to treat POME. The ratio of volatile solids/total solids (VS/TS) and volatile fatty acids in the anaerobic sludge in the UASB reactor decreased significantly after long-term operation due to the precipitation of calcium carbonate in the granules. Granulation and methanogenesis decreased with an increase in the influent CaO–CKD concentration.

Dynamic modeling of sulfate reducing biofilms

This paper presents a mathematical model able to simulate the physical, chemical and biological processes prevailing in a sulfate reducing biofilm under dynamic conditions. A mathematical modeling approach for microbial growth and decay is proposed. Complete oxidizers sulfate reducing bacteria, incomplete oxidizers sulfate reducing bacteria and acetate degraders are the microbial groups taken into account in the model. The proposed model is able to simulate the competition among the bacteria growing in the biofilm. The method of characteristics is introduced for the numerical process. As in the qualitative analysis of solutions, where it was first presented, this method seems to be a powerful tool in this situation also. The model has been applied to simulate the sulfate reduction process in a biofilm for several purposes. In particular the effect of the COD / SO 4 2 − ratio and the effect of different simulation times on the reactor performances in terms of volume fraction of bacterial species and substrate diffusion trends in biofilm have been assessed.

Development of a kinetic model for anaerobic dry digestion processes: Focus on acetate degradation and moisture content

The objective of this work is to develop a kinetic model to specifically assess the degradation of the organic fraction of municipal solid waste (OFMSW) in dry anaerobic digestion processes. The model description was designed to include several aspects of dry digestion such as the presence of particulate matter and high solid content. The global structure of the kinetic model proposed here is based on the ADM1 (Anaerobic Digestion Model n° 1) which has been modified in order to include specific characteristics of dry media. Batch experimental data of methane production with acetate as organic substrate under dry mesophilic conditions have been obtained and used to calibrate the kinetic parameters associated to acetate uptake. The model was shown to simulate well batch degradation of acetate and methane production in dry mode. The biochemical parameters associated to acetate degradation kinetics were the maximal acetate uptake rate ( k m X ac) and the half-saturation constant K S ac . After calibration, the value of k m X ac was 440 mg COD kg −1 d −1 and K S ac was 290 mg COD kg −1 for a moisture content (MC) of 82%. The value of K s was found to be higher in dry digestion than the recommended value in wet digestion. It increased from 290 mg COD kg −1 at 82% MC up to 2000 mg COD kg −1 at 65% MC. This result was attributed to diffusion limitations due to the singular “pasty” aspect of the digesting medium.

Rapid start-up of thermophilic anaerobic digestion with the turf fraction of MSW as inoculum

This study aims to determine suitable start-up conditions and inoculum sources for thermophilic anaerobic digestion. Within days of incubation MSW at 55°C, methane was produced at a high rate. In an attempt to narrow down which components of typical MSW contained the thermophilic methanogens, vacuum cleaner dust, banana peel, kitchen waste, and garden waste were tested as inoculum for thermophilic methanogenesis with acetate as the substrate. Results singled out grass turf as the key source of thermophilic acetate degrading methanogenic consortia. Within 4days of anaerobic incubation (55°C), anaerobically incubated grass turf samples produced methane accompanied by acetate degradation enabling successful start-up of thermophilic anaerobic digestion. Other essential start-up conditions are specified. Stirring of the culture was not conducive for successful start-up as it resulted specifically in propionate accumulation.

Syntrophic acetate oxidation under thermophilic methanogenic condition in Chinese paddy field soil

The aim of the present work was to determine and compare the degradation of acetate in a Chinese rice field soil at 25°C and 50°C, respectively, and to identify specifically the active organisms involved in syntrophic acetate oxidation. Soil was preincubated anaerobically for 30 days to reduce alternative electron acceptors other than CO(2). The [2-(13)C] acetate (99% (13)C) was added twice: 0 day and 19 days after preincubation. Addition of [2-(13)C] acetate resulted in an immediate increase of (13)C labeled CH(4) but non-labeling of CO(2) at 25°C. The methanogen community was dominated by Methanosarcinaceae and Methanocellales at 25°C. In contrast, the addition of [2-(13)C] acetate at 50°C resulted in a rapid increase of (13)CO(2). The (13)C labeling of CH(4) gradually increased and reached a similar value to CO(2) (13% (13)C) at the end of incubation (40 days). Nearly all archaeal 16S rRNA genes detected at 50°C belonged to hydrogenotrophic Methanocellales. DNA-based stable isotope probing analysis revealed that the organisms related to Thermacetogenium lineage and the unclassified Thermoanaerobacteraceae group were intensively labeled with (13)C in the incubations at 50°C. Thus, acetate was converted to CH(4) and CO(2) through aceticlastic methanogenesis at 25°C, while syntrophic acetate oxidation occurred at 50°C.

Changes in the Acetogenic Population in a Mesophilic Anaerobic Digester in Response to Increasing Ammonia Concentration

Changes in the acetogenic population were investigated in an experimental laboratory-scale biogas reactor (37°C) subjected to gradually elevated ammonia levels (0.8 to 6.9 g NH(4)(+)-N L(-1)). A shift from aceticlastic acetate degradation to syntrophic acetate oxidation had previously been confirmed in this reactor. In a parallel control reactor, operating at constant ammonia levels (0.65-0.90 g NH(4)(+)-N L(-1)), acetate degradation proceeded via the aceticlastic pathway throughout the operating period (660 d). The acetogenic populations in the reactors were analysed using degenerated primers designed to target the functional gene encoding a key enzyme of the acetyl-CoA pathway, 10-formyltetrahydrofolate synthetase (FTHFS). The analysis consisted of terminal restriction fragment length polymorphism (T-RFLP) analysis coupled with the construction of clone libraries, and quantitative PCR (qPCR) analysis. The T-RFLP data obtained were statistically analysed by non-metric multidimensional scaling. The most abundant FTHFS genes recovered in the clone libraries were assigned to terminal restriction fragments of the T-RFLP profile. The results of the investigation clearly indicated that increased ammonia concentration substantially influenced the putative acetogenic population structure and caused two distinct shifts of the most abundant members; however, the identity of the dominating species remains unknown, as none of the genes had been identified previously. Despite the shifts in the population, the qPCR analysis revealed a relatively stable abundance of the acetogenic population throughout the operation.

Effect of Corrosion Inhibitors on Oxidative Degradation of MEA in Carbon Dioxide Capture

The effect of corrosion inhibitors such as CuCO3, CuSO4, and Na2SO3 on the oxidation of MEA has been investigated. The products of oxidative degradation of MEA were analyzed with or without the corrosion inhibitors. The corrosion inhibitor effects on the oxidative degradation of MEA and the extent of oxidative degradation is in the order CuCO3 > CuSO4 > MEA without inhibitors > Na2SO3. There was no difference in absorption/desorption rates among MEA solutions with and without the corrosion inhibitors. Among the products of the oxidative degradation of MEA, formate and acetate were dominant degradation products and nitrites and nitrates were also present in large amounts. The corrosion inhibitors CuCO3 and CuSO4 acted as catalysts for oxidative degradation of MEA. CuCO3 and CuSO4 influenced the formation of carboxylic acids (formate, acetate, and oxalate), but did not influence the formation of nitrogen products (nitrites and nitrates). Na2SO3 slightly inhibited the oxidative degradation of MEA and did not produce more oxidation products than CuCO3 and CuSO4.

Predominant Contribution of Syntrophic Acetate Oxidation to Thermophilic Methane Formation at High Acetate Concentrations

To quantify the contribution of syntrophic acetate oxidation to thermophilic anaerobic methanogenesis under the stressed condition induced by acidification, the methanogenic conversion process of 100 mmol/L acetate was monitored simultaneously by using isotopic tracing and selective inhibition techniques, supplemented with the analysis of unculturable microorganisms. Both quantitative methods demonstrated that, in the presence of aceticlastic and hydrogenotrophic methanogens, a large percentage of methane (up to 89%) was initially derived from CO(2) reduction, indicating the predominant contribution of the syntrophic acetate oxidation pathway to acetate degradation at high acid concentrations. A temporal decrease of the fraction of hydrogenotrophic methanogenesis from more than 60% to less than 40% reflected the gradual prevalence of the aceticlastic methanogenesis pathway along with the reduction of acetate. This apparent discrimination of acetate methanization pathways highlighted the importance of the syntrophic acetate-oxidizing bacteria to initialize methanogenesis from high organic loadings.

Effects of engineered nanomaterials on microbial catalyzed biogeochemical processes in sediments

Engineered nanomaterials (ENMs) are anticipated to find use in many human activities and commercial products. Concerns are therefore being raised regarding their environmental fate and toxicological implications, which remain largely unknown. In this study, we investigate the effects of C60, nano-Ag and CdSe quantum dots (QD) on microbial-catalyzed oxidation of organic matter in freshwater sediments. Sediment slurries spiked with sodium acetate at a final concentration of 150mg/L were separately treated with pre-identified toxic levels of the tested ENMs. The study focused primarily on acetate oxidation by nitrate reducing bacteria. Sediment slurries were incubated under anaerobic conditions in parallel with control samples, and changes in concentrations of acetate, nitrate and nitrite tracked over time. The results showed that tested C60 concentration completely inhibited the microbial oxidation of acetate, whereas the addition of nano-Ag and CdSe QD to sediment slurries negatively affected the rates of acetate oxidation. Under conditions with nitrate as prevalent electron acceptor, reaction rates of acetate degradation decreased from 0.44 day−1 in control slurries to 0.24 day−1 and 0.20 day−1 in slurries treated with nano-Ag and CdSe QD, respectively. These preliminary results call for further investigations on potential long-term effects of ENMs on microbial driven basic ecosystem services.

Identification of methanogenic pathways in anaerobic digesters using stable carbon isotopes

AbstractIn a series of anaerobic batch experiments, the stable carbon isotopes, δ13CCH?4? and δ13CCO?2?, were measured in biogas produced from various sources (maize, cellulose, inoculum) to identify the degradation kinetics and specific methanogenic pathways. Isotopic analysis was performed using a new absorption laser spectrometer in addition to conventional MS. A comparison of the isotopic evolution shows large isotope dynamics for maize and cellulose, indicating a temporal change in degradation pathways and/or a change in the relative contribution from different carbon fractions within the substrate. Further batch experiments with isotopically labelled acetate (either 13CH3CO2Na or CHCO2Na) were carried out to study the degradation of acetate in inoculum systematically. The results suggest that the acetate is completely oxidized into CO2 which in turn is partly reduced to CH4. Furthermore, the distinct isotopic signature CH4 and CO2 (for acetate‐methyl labelling as well as for acetate‐carboxy labelling) indicate that only a minor part of the produced methane derives from acetate. A substantial fraction of methane may have been produced at an earlier stage of the reaction chain or by other potential methane precursors such as formate or methanol.

Thermal degradation of cellulose acetate in presence of bis-phosphoramidates

Novel bis-phosphoramidate compounds phosphoramidic acid, 1,2-ethanediylbis-, tetraethylester (PAEDBTEE) and phosphoramidic acid, 1,4-piperazinediylbis-, tetraethylester (PAPDBTEE) were synthesized as potential flame retardants. Films of cellulose acetate (CA) were prepared by addition of these compounds as flame retardants. The burning tests such as limiting oxygen index and small scale fire test showed improved flame protection of CA in presence of these bis-phosphoramidates. Thermal decomposition studies carried out using pyrolysis combustion flow calorimetry (PCFC) and thermal gravimetric analyzer showed that addition of bis-phosphoramidate increased the peak heat release rates and char content but decreased the total heat of combustion. Further analysis performed using evolved gas analysis techniques such as thermo gravimetric analyzer–Fourier transform infrared spectroscopy (TGA–FTIR) and pyrolysis gas chromatography mass spectrometry (Py-GC–MS) provided insights into the decomposition pathways of cellulose in presence of these additives. The novel compounds were tested for toxicity using Microtox test and were found to be relatively less toxic as compared to phenol and a commercially available flame retardant.

Functional Analysis of the Carbohydrate-Binding Module of an Esterase from Neisseria sicca SB Involved in the Degradation of Cellulose Acetate

An esterase gene from Neisseria sicca SB encoding CaeA, which catalyzes the deacetylation of cellulose acetate, was cloned. CaeA contained a putative catalytic domain of carbohydrate esterase family 1 and a carbohydrate-binding module (CBM) family 2. We constructed two derivatives, with and without the CBM of CaeA. Binding assay indicated that the CBM of CaeA had an affinity for cellulose.

A comparative study of biodegradation of vinyl acetate by environmental strains

Four Gram-negative strains, E3_2001, EC1_2004, EC3_3502 and EC2_3502, previously isolated from soil samples, were subjected to comparative studies in order to select the best vinyl acetate degrader for waste gas treatment. Comparison of biochemical and physiological tests as well as the results of fatty acids analyses were comparable with the results of 16S rRNA gene sequence analyses. The isolated strains were identified as Pseudomonas putida EC3_2001, Pseudomonas putida EC1_2004, Achromobacter xylosoxidans EC3_3502 and Agrobacterium sp. EC2_3502 strains. Two additional strains, Pseudomonas fluorescens PCM 2123 and Stenotrophomonas malthophilia KB2, were used as controls. All described strains were able to use vinyl acetate as the only source of carbon and energy under aerobic as well as oxygen deficiency conditions. Esterase, alcohol dehydrogenase and aldehyde dehydrogenase were involved in vinyl acetate decomposition under aerobic conditions. Shorter degradation times of vinyl acetate were associated with accumulation of acetic acid, acetaldehyde and ethanol as intermediates in the culture fluids of EC3_2001 and KB2 strains. Complete aerobic degradation of vinyl acetate combined with a low increase in biomass was observed for EC3_2001 and EC1_2004 strains. In conclusion, P. putida EC1_2004 is proposed as the best vinyl acetate degrader for future waste gas treatment in trickle-bed bioreactors.

Degradation of citronellol, citronellal and citronellyl acetate by Pseudomonas mendocina IBPse 105

The purpose of this work was to stud the biodegradation of citronellol, citronellal and citronellyl acetate by a soil Pseudomonas mendocina strain (IBPse 105) isolated from a Cymbopogon windelandi field. This strain efficiently used citronellol, citronellal, citronellyl acetate and myrcene as sole source of carbon, but was not able to grow on other 15 monoterpenoids evaluated. Gas chromatography-mass spectrometry (GC-MS) analysis of metabolites accumulation during P. medocina IBPse 105 growth on citronellol showed that this strain uses the citronellol catabolic pathway described for other species of the genus. IBPse 105 degradation of citronellyl acetate initiates by its hydrolysis to citronellol. The mini-Tn5 insertion in mutant IBPse 105-303, impaired in citronellol degradation, but able to grow on citronellal, was located in a homologous of the P. aeruginosa atuB gene, that codifies citronellol deshydrogenase.

Vinyl acetate degradation by Brevibacillus agri isolated from a slightly aerated methanogenic reactor

In a previous paper, the authors showed that a slight aeration of a methanogenic reactor treating wastewater from the manufacture of polymeric resins could improve its performance, by increasing or allowing the removal of some of its contaminants, including vinyl acetate (VA). This paper reports the isolation under aerobic conditions of a VA‐biodegrading axenic culture (strain C1) retrieved from the sludge of a slightly aerated methanogenic reactor at 1 mg L−1 d−1 of dissolved oxygen (DO). The axenic culture obtained was phenotypically (morphology, biochemical properties, VA consumption kinetics) and phylogenetically characterized. It formed white colonies with a branched and flat morphology on solid medium. The cell morphology of the isolate was bacillus with round endings and flagellate. The cells could form chains and were stained Gram‐negative. The isolate required simple nutritional elements and had a growth rate of 0.024 h−1. The phylogenetical analysis showed that the aerobic bacterium was identified as Brevibacillus agri, with 99.3% similarity. The VA consumption kinetics in the methanogenic sludge were: volumetric consumption rate (rVA) of 1.74 ± 0.2 mg L−1 h−1, maximum specific consumption rate (qVAmax) of 3.98 mg g−1 volatile suspended solids (VSS) h−1 and affinity constant (KS) of 457.1 mg L−1. The same parameters in the axenic culture were 1.69 ± 0.04 mg L−1 h−1, 4.09 mg g−1 dry weight h−1 and 421.9 mg L−1, respectively. These results show evidence that the aerobic isolated bacterium, identified as Brevibacillus agri, carried out the VA hydrolysis in the slightly aerated methanogenic sludge, which is the limiting step in the degradation of this compound.

Cytoplasmic acidification and the benzoate transcriptome in Bacillus subtilis.

Background Bacillus subtilis encounters a wide range of environmental pH. The bacteria maintain cytoplasmic pH within a narrow range. Response to acid stress is a poorly understood function of external pH and of permeant acids that conduct protons into the cytoplasm.Methods and Principal FindingsCytoplasmic acidification and the benzoate transcriptome were observed in Bacillus subtilis. Cytoplasmic pH was measured with 4-s time resolution using GFPmut3b fluorimetry. Rapid external acidification (pH 7.5 to 6.0) acidified the B. subtilis cytoplasm, followed by partial recovery. Benzoate addition up to 60 mM at external pH 7 depressed cytoplasmic pH but left a transmembrane ΔpH permitting growth; this robust adaptation to benzoate exceeds that seen in E. coli. Cytoplasmic pH was depressed by 0.3 units during growth with 30 mM benzoate. The transcriptome of benzoate-adapted cells was determined by comparing 4,095 gene expression indices following growth at pH 7, +/− 30 mM benzoate. 164 ORFs showed ≥2-fold up-regulation by benzoate (30 mM benzoate/0 mM), and 102 ORFs showed ≥2-fold down-regulation. 42% of benzoate-dependent genes are regulated up or down, respectively, at pH 6 versus pH 7; they are candidates for cytoplasmic pH response. Acid-stress genes up-regulated by benzoate included drug resistance genes (yhbI, yhcA, yuxJ, ywoGH); an oligopeptide transporter (opp); glycine catabolism (gcvPA-PB); acetate degradation (acsA); dehydrogenases (ald, fdhD, serA, yrhEFG, yjgCD); the TCA cycle (citZ, icd, mdh, sucD); and oxidative stress (OYE-family yqjM, ohrB). Base-stress genes down-regulated by benzoate included malate metabolism (maeN), sporulation control (spo0M, spo0E), and the SigW alkali shock regulon. Cytoplasmic pH could mediate alkali-shock induction of SigW.Conclusions B. subtilis maintains partial pH homeostasis during growth, and withstands high concentrations of permeant acid stress, higher than for gram-negative neutralophile E. coli. The benzoate adaptation transcriptome substantially overlaps that of external acid, contributing to a cytoplasmic pH transcriptome.

Contribution of Microbial Activity to Carbon Chemistry in Clouds

The biodegradation of the most abundant atmospheric organic C1 to C4 compounds (formate, acetate, lactate, succinate) by five selected representative microbial strains (three Pseudomonas strains, one Sphingomonas strain, and one yeast strain) isolated from cloud water at the puy de Dôme has been studied. Experiments were first conducted under model conditions and consisted of a pure strain incubated in the presence of a single organic compound. Kinetics showed the ability of the isolates to degrade atmospheric compounds at temperatures representative of low-altitude clouds (5 degrees C and 17 degrees C). Then, to provide data that can be extrapolated to real situations, microcosm experiments were developed. A solution that chemically mimicked the composition of cloud water was used as an incubation medium for microbial strains. Under these conditions, we determined that microbial activity would significantly contribute to the degradation of formate, acetate, and succinate in cloud water at 5 degrees C and 17 degrees C, with lifetimes of 0.4 to 69.1 days. Compared with the reactivity involving free radicals, our results suggest that biological activity drives the oxidation of carbonaceous compounds during the night (90 to 99%), while its contribution accounts for 2 to 37% of the reactivity during the day, competing with photochemistry.