Acetate Removal Research Articles

Evaluation of operating conditions on sulfate reduction from acidic wastewater in a fixed-bed bioreactor

The removal of sulfate derived from mine impacted waters is a major objective when treatment is focused on removing potentially toxic metals and metalloids, and neutralizing the acidity of these polluting waters. Here we report on the use of a mixed culture fixed-film column bioreactor including one acidophilic sulfidogen operated for 270 days to primarily remove sulfate from an acidic synthetic water that contained a low level of zinc (0.15 mM). Changing the hydraulic retention time (HRT) from 100 to 30 h caused minor perturbations in the removal of sulfate (∼40%) using 6 mM of glycerol as carbon and electron source; however, lowering the HRT to 25 h did not sustain biosulfidogenesis. By increasing the concentration of glycerol as electron donor to catalyze the dissimilatory reduction of sulfate, it was possible to reduce the concentration of sulfate from 14 mM to ∼3 mM. This corresponded to an ∼80% removal efficiency from the acidic water feedstock, which is well below the lowest attainable concentration using conventional technologies such as gypsum precipitation. Molecular analyses of the column effluent demonstrated that the mixed culture population changed with varying concentrations of glycerol, highlighting a role for Clostridium sp. in the degradation (removal) of acetate produced in the bioreactor by Desulfosporosinus acididurans.

Highly efficient UV-visible-infrared photothermocatalytic removal of ethyl acetate over a nanocomposite of CeO2 and Ce-doped manganese oxide

A unique nanocomposite of CeO2 nanoparticles and Ce-doped manganese oxide nanofibers having a crystalline cryptomelane-type octahedral molecular sieve (KMn8O16·nH2O, abbreviated as OMS-2) structure (denoted CeO2-CeOMS-2) was prepared by the reaction of Ce(NO3)3 and KMnO4 at 90 °C. CeO2-CeOMS-2 shows extremely high photothermocatalytic activity, very low selectivity for acetaldehyde (an unfavorable byproduct), and excellent durability for ethyl acetate removal under UV-visible-infrared (UV-vis-IR) irradiation. In striking contrast, pure CeO2, pure OMS-2, and TiO2 (P25) showed much lower photothermocatalytic activities and higher selectivities for acetaldehyde. The CO2 production rate within the first five minutes (rCO2) of reaction with CeO2-CeOMS-2 was as high as 1102.5 μmol g–1 min–1, which is 137, 17, and 30-times higher than those of pure CeO2, pure OMS-2, and TiO2 (P25), respectively. CeO2-CeOMS-2 also shows good photothermocatalytic activity under vis-IR (λ > 420 or 560 nm) irradiation. Further, even under vis-IR (λ > 830 nm) irradiation, efficient photothermocatalytic activity was achieved. In addition, the catalytic activity of CeO2-CeOMS-2 is far superior to those of pure CeO2 and OMS-2, which is attributed to the fact that Ce doping significantly improves the lattice oxygen activity of OMS-2. The high photothermocatalytic activity of CeO2-CeOMS-2 arises from the synergy between the photocatalytic effect of the CeO2 nanoparticles and light-driven thermocatalysis of the Ce-doped OMS-2. The novel photoactivation of Ce-doped OMS-2, which is unlike that of conventional photocatalysis on semiconductor photocatalysts, further promotes the catalytic activity because the surface oxygen activity of Ce-doped OMS-2 is promoted upon UV-vis-IR or vis-IR (λ > 560 nm) irradiation.

Efficient recovery of carboxylates from the effluents treated by advanced oxidation processes using flow-electrode capacitive deionization in short-circuited closed-cycle operation

• Acetate and oxalate can be effectively recovered from wastewater using FCDI. • Carbon flow-electrodes of FCDI facilitated the decrease of cell voltage. • FCDI in SCC operation showed high removal efficiency of anions, low energy consumption and stable desalination. • High selective recovery of oxalate could be realized by adjusting influent pH. Advanced oxidation processes (AOPs) are highly efficient novel methods for a wide range of organic substances. However, the decomposition of organic pollutants usually results in the formation of a series of carboxylates that are difficult to be further degraded by oxidants, which not only induces the excessive consumption of chemicals, but also leads to waste of carbon resources. Therefore, the recovery of small molecular carboxylates from effluents is a significant strategy. However, the excessive high voltage in conventional electrochemical technology for recovering small molecule acids can easily lead to organic matter degradation and high energy consumption. In present study, the removal and recovery of refractory acetate and liable oxalate by using FCDI system operated in short-circuited closed-cycle (SCC) operation was investigated. The results showed that Ac − and Ox − could be effectively accumulated in anode chamber from wastewater containing high-strength of Cl − . The significance of carbon flow-electrodes for the recovery performance and operating cost was evidenced. Higher carbon conditions induced an obvious decrease of cell voltage and thus the decomposition of organic compounds and energy consumption were decreased simultaneously. On the premise of the recovery rate, under the optimal conditions (carbon = 5 wt%, j = 5.7 A/m 2 , HRT = 7.45 min, pH i = 7.1 and t = 180 min), more than 80% of acetate and oxalate can be recovered from wastewater with a low energy consumption of 0.45 kWh/m 3 . The calculated average salt recovery rates (ASRR r ) for Ac − and Ox − were 0.186 and 0.45 μmol/(cm 2 ·min), respectively. The findings indicated that FCDI system with carbon particle flow-electrode operating in SCC mode is a promising strategy for continuously recovering aqueous carboxylates. In further research, combining FCDI operation with other techniques such as AOPs is possible to realize simultaneous oxidation and carboxylates recovery, in other words, in-situ product recovery, that if recovered will greatly contribute to the sustainability of the low carbon economy.

Physiological metabolism of electrochemically active bacteria directed by combined acetate and Cd(II) in single-chamber microbial electrolysis cells

It is of great interest to explore physiological metabolism of electrochemically active bacteria (EAB) for combined organics and heavy metals in single-chamber microbial electrolysis cells (MECs). Four pure culture EAB varying degrees responded to the combined acetate (1.0–5.0 g/L) and Cd(II) (20–150 mg/L) at different initial concentrations in the single-chamber MECs, shown as significant relevance of Cd(II) removal (2.57–7.35 mg/L/h) and H2 production (0–0.0011 m3/m3/h) instead of acetate removal (73–130 mg/L/h), to these EAB species at initial Cd(II) below 120 mg/L and initial acetate below 3.0 g/L. A high initial acetate (5.0 g/L) compensated the Cd(II) inhibition and broadened the removal of Cd(II) to 150 mg/L. These EAB physiologically released variable amounts of extracellular polymeric substances with a compositional diversity in response to the changes of initial Cd(II) and circuital current whereas the activities of typical intracellular enzymes were more apparently altered by the initial Cd(II) than the circuital current. These results provide experimental validation of the presence, the metabolic plasticity and the physiological response of these EAB directed by the changes of initial Cd(II) and acetate concentrations in the single-chamber MECs, deepening our understanding of EAB physiological coping strategies in metallurgical microbial electro-ecological cycles.

Comparative study between biological treatment and a physicochemical treatment for the removal of Butyl Acetate in industrial residual effluents

A comparison was made between a fixed aerobic biological process and a physicochemical treatment for waste effluents with butyl acetate. An acrylic tank with 100 L capacity and a support medium for PET bottles was implemented for the formation of the biofilm and thus develop the biological reactor. In the experimental phase, concentrations of 10, 20 and 30% of butyl acetate containing sample, using hydraulic retention times of: (16, 8, 5.33 and 4 days) for each concentration. After the experimentation, a removal of 99% of COD and 97% of BOD was obtained. For the physicochemical treatment, coagulant, flocculant, and adjuvants were used, by a jar test. A decrease in 74%, 53.8%, 55%, 97% and 37%, for electrical conductivity, total suspended solids, color, turbidity, COD and BOD respectively, were obtained compared to the initial sample. Both treatments were filtered through a bed packed with activated carbon, sand, and silica gravel. The aim of this work was to evaluate / quantify butyl acetate removal efficiency in each treatment for its subsequent comparison, with prospect to the reduction of similar pollutants in residual effluents is intended.

Performance of a fungal-biofilter for simultaneous removal of hydrogen sulfide and butyl acetate

Performance of a fungal-biofilter for simultaneous removal of hydrogen sulfide and butyl acetate

Removal of ethyl acetate in air by using different types of corona discharges generated in a honeycomb monolith structure coated with Pd/γ-alumina

A method based on the corona discharge produced by high voltage alternating current (AC) and direct current (DC) over a Pd/γ-Al2O3 catalyst supported on a honeycomb structure monolith was developed to eliminate ethyl acetate (EA) from the air at atmospheric pressure. The characteristics of the AC and DC corona discharge generated inside the honeycomb structure monolith were investigated by varying the humidity, gas hourly space velocity (GHSV), and temperature. The results showed that the DC corona discharge is more stable and easily operated at different operating conditions such as humidity, GHSV, and gas temperature compared to the AC discharge. At a given applied voltage, the EA conversion in the DC honeycomb catalyst discharge is, therefore, higher compared with that in the AC honeycomb catalyst discharge (e.g., 96% of EA conversion compared with approximately 68%, respectively, at 11.2 kV). These new results can open opportunities for wide applications of DC corona discharge combined with honeycomb catalysts to VOC treatment.

Co3O4 nanoparticles with different morphologies for catalytic removal of ethyl acetate

Nanosized Co3O4 with different morphologies (rods-like (NR-), flowers-like (NF-), cages-like (NC-) and single crystal (NP-)) were synthesized by using hydrothermal and co-precipitation methods and applied in catalytic removal of ethyl acetate (EA). Complete EA conversion under a space velocity of 30,000 mL/ (g h) are shown at 210 °C for NP-Co3O4. The results of physicochemical properties reveals that NP-Co3O4 catalyst performs the best catalytic activity for EA oxidation attributed to larger specific surface area, better low-temperature reducibility, abundant Co3+ cationic species exposed on the (220) plane and sufficiently active surface oxygen species.

Boosting the photocatalytic degradation of ethyl acetate by a Z-scheme Au–TiO2@NH2-UiO-66 heterojunction with ultrafine Au as an electron mediator

A Z-scheme Au–TiO2@NH2-UiO-66 photocatalyst with ultrafine Au as electron mediator was synthesized, which exhibited an exceptionally high mineralization efficiency of 85% at 94.6% ethyl acetate removal under visible light irradiation.

Optimization of pretreatment in pymetrozine production wastewater via reactive distillation and side-stream distillation methods with response surface methodology.

Lots of highly concentrated saline organic wastewater is produced during the pymetrozine production process, causing environmental pollution and waste of resources if discharged directly. Research on actual pymetrozine wastewater treatment is quite scarce. Existing treatment methods of pesticide wastewater usually have disadvantages of long treatment time, low processing efficiency and low recovery rate. To solve these problems, a pretreatment process for pymetrozine wastewater was studied based on material recovery and pollutant degradation. The ammonia conversion process was experimentally investigated by reactive distillation. The reaction product vapor was neutralized and then separated by side-stream distillation. Aspen Plus and response surface methodology were employed to simulate and optimize the operating conditions. Box-Behnken design was used to investigate the individual and interaction effects on methanol purification and sodium acetate removal. Experimental study was carried out on the basis of theoretical simulation data. The result showed that the optimized methanol content on tower top was 99.28% with a yield of 99.95% and methanol content of side withdrawal was 0.01%. The process can be applied for pesticide wastewater treatment to recycle high purity chemical materials, and meets the national sewage comprehensive emission standard.

Performance characterization of nanofiltration, reverse osmosis, and ion exchange technologies for acetic acid separation

A major obstacle to widespread implementation of bio-based fuels and chemicals is the lack of efficient and cost-effective separation methods. To purify acetic acid produced by biochemical conversion of biomass via anaerobic digestion, this work employs two commonly used separation technologies: (1) ion-exchange (IX) resin and (2) pressure-driven membranes. This study tested five commercially available strong- and weak-base anion-exchange resins and five commercially available nanofiltration (NF) and reverse osmosis (RO) membranes. The pH of the feed solution significantly affected adsorption capacity. At pH 6.3, a strong-base IX resin (IRN-78) performed best (95.1% acetate removal). With strong-base IX resins, the Langmuir isotherm model fit well, whereas for weak-base IX resins, the Freundlich isotherm provided a better fit. A pseudo-second-order kinetic model fit well for both IRN-78 and IRA-67. Regarding membrane separation, RO (BW30XFR membrane) achieved the highest rejection (98.6% acetate rejection), whereas an NF membrane (NF*) achieved the best combination of permeate flux (105 L/(h·m2)) and rejection (83.1% acetate rejection). For membrane performance, the experimental data were fit using the solution diffusion model. Increased pH in the feed solution lowered permeate flux but increased acetic acid rejection. When the acetic acid concentration in the feed solution increased, both permeate flux and acetic acid rejection decreased for membrane NF*.

Steady-state operation of a biofilter coupled with photocatalytic control of bacterial bioaerosol emissions.

Bioaerosols are emitted during the biological treatment of water, soil, and air pollutants. The elimination of these pollutants has become a priority due to their detrimental effects on human health. Advanced oxidation technologies have been used to control bioaerosol emissions specially to improve indoor air quality. This investigation was focused on evaluating the biofiltration of ethyl acetate vapors in terms of removal efficiency and bioaerosol emission. Also, a continuous photocatalytic process to inactivate bioaerosols emitted from the biofilter was assessed as a post-treatment. The photocatalysis was developed with ZnO and TiO2 immobilized onto Poraver glass beads. Flow cytometry (FC) coupled with fluorochromes was used to characterize and quantify bioaerosol emissions in terms of live, dead, and injured cells. Ethyl acetate removal efficiencies were maintained in a steady state with values of 100% under 60-gm-3h-1 inlet load (IL). Biomass concentration in the biofilter reached values up to 228mgbiomassgperlite-1 at day 56 of operation, but the spontaneous occurrence of predatory mites diminished biomass concentration by 33%. Bioaerosols emitted during the steady-state operation of the biofilter were composed mainly by bacteria (~ 94%) and in a less extent of fungal spores (0.29-6%). The most efficient photocatalytic system comprised TiO2/Poraver with 78% inactivation of bioaerosols during the first 2h of the process, whereas the ZnO/Poraver system showed null activity (~ 0%) of inactivation. FC results show that the main mechanism of inactivation of TiO2/Poraver was cell death.

Catalytic decomposition of ethyl acetate over La-modified Cu–Mn oxide supported on honeycomb ceramic

The La-modified Cu–Mn spinel oxide was successfully coated onto honeycomb ceramic by a wash-coating method for complete catalytic decomposition of ethyl acetate. The La-modified Cu–Mn oxides were characterized by X-ray diffraction, X-ray fluorescence, H2-temperature programmed reduction, Brunauer-Emmett-Teller method, field-emission scanning electron microscopy and high-resolution transmission electron microscopy. The effects of different precipitants and rare earth doping on the structure and catalytic performance of the catalysts were investigated. The results show that the CuMn2O4 spinel with (NH4)2CO3 as a precipitant can form a larger specific surface area and a suitable pore size, which is beneficial to the absorption of ethyl acetate. Although the rare earth doping does not significantly change the crystal phase structure of the catalyst, it improves its reducibility and lowers the temperature of the catalytic decomposition. With respect to the catalytic decomposition of ethyl acetate, the rare earth-modified Cu–Mn oxide supported on honeycomb ceramic shows excellent catalytic performance with 100% conversion under the conditions of 239 °C, space velocity of 12500 h−1 and 1000 ppm. And the ethyl acetate removal rate is still 100% after 1440 min of continuous reaction.

Hydrogen production in two-chamber MEC using a low-cost and biodegradable poly(vinyl) alcohol/chitosan membrane

Hydrogen production was evaluated in two-chamber microbial electrolysis cells (MEC), where the chambers of the cell were separated using a new economical and environmentally friendly membrane made of poly (vinyl) alcohol/chitosan (PVA/CS). The MEC performance was compared to that of Nafion. The obtained results indicated that the MEC performance for hydrogen production did not show significant differences between the PVA/CS and Nafion membranes. MEC with PVA/CS showed the hydrogen production rate and hydrogen yield of 1277 ± 46 mL H2Lcat−1d−1 and 974 ± 116 mL H2 gacetate−1, respectively. The PVA/CS membrane allowed acetate removal that was 7% higher than that of Nafion due to the lower pH gradient and a lower voltage drop that increased the ion transfer across the membrane.

A Practical Synthesis of [(tmeda)Ni(CH3)2], Isotopically Labeled [(tmeda)Ni(13CH3)2], and Neutral Chelated-Nickel Methyl Complexes

A practical procedure for the synthesis of N,N,N′,N′-tetramethylethylene diamine nickel dimethyl, [(tmeda)Ni(CH3)2] (5), based on commercially available methyllithium and [(tmeda)Ni(acac)2] (1) (acac = acetylacetonate), [(tmeda)Ni(OAc)2] (2) (OAc = acetate), [(tmeda)NiSO4] (3), or [(tmeda)NiF2] (4) has been developed. With 2 as the starting material, reproducible isolation of >14 g (ca. 68 mmol, 85%) of 5 in one-batch reactions is feasible. This synthetic route also enables the formation and isolation of 13C-labeled [(tmeda)Ni(13CH3)2] (5-13CH3) starting from 13CH3I by intermediate isolation of [(tmeda)2–3(Li13CH3)4]x (10). The amount of iodide impurities in 10 to push back iodide-catalyzed decomposition of 5-13CH3 to ethane and nickel black by a Kumada-type coupling is essential for successful isolation of 5-13CH3. [(tmeda)Ni(OAc)2] (2) is a superior nickel precursor to 5 in comparison to [(tmeda)Ni(acac)2] (1), as (a) removal of lithium acetate (9) from the crude reaction mixture is much easier than removal of lithium acetylacetonate and (b) κ2-N,O-salicylaldiminato nickel methyl complexes (12) or a κ2-P,O-phosphinesulfonato nickel methyl complex (14) can be easily prepared in a one-pot procedure starting from 2, methyllithium, and salicylaldimines (11) or phosphoniumsulfonate (13), respectively. The X-ray diffraction analyses of 2, 5, and 12b-PPh3 are reported.

Twin-chain polymer networks loaded with nanostructured fluids for the selective removal of a non-original varnish from Picasso\u2019s \u201cL\u2019Atelier\u201d at the Peggy Guggenheim Collection, Venice

This paper reports on the evaluation of a polyvinyl alcohol (PVA) “twin-chain” polymer network (TC-PN) combined with an oil-in-water nanostructured fluid (NSF) for the removal of a polyvinyl acetate (PVAc) varnish. Small Angle X-ray Scattering, Confocal Laser Scanning Microscopy, and Fluorescence Correlation Spectroscopy showed that the structure of the gel and the NSF are only minimally altered by loading the fluid into the gel. The NSF is partially free to diffuse through the network, but also interacts with the gel walls. During the cleaning, the dynamics of the fluid at the gel-substrate interface are controlled by the osmotic balance taking place among the interconnected pores. These features grant effective and controlled cleaning performances. The case study identified for this research is Pablo Picasso’s The Studio (L’Atelier, 1928), one of the masterpieces in the Peggy Guggenheim Collection, Venice (PGC). In 1969 the oil painting, originally unprotected, was wax-lined and then varnished using a PVAc varnish. Over the years, the white shades of the painting have been compromised by the yellowing of the varnish and soiling of deposits. On painting mock-ups, the NSF-loaded hydrogels allowed the swelling and softening of PVAc varnish and wax layers, which were then removed with gentle mechanical action. Effective varnish and wax removal at the micron scale, and the absence of residues from the cleaning system (gel and NSF), were confirmed by Fourier Transform Infrared Spectroscopy (FTIR) 2D imaging. The effective and safe removal of the aged PVAc varnish and wax layer from the surface of the painting was then carried out using the same cleaning protocol successfully tested on the mock-ups, setting the NSF-loaded PVA TC-PNs as robust and reliable tools for the cleaning of sensitive works of art.

Removal of ethyl acetate by plasma enhanced with jet flows

Non-thermal plasma is widely used for the removal of volatile organic compounds owing to the various advantages of this technique, which include being maneuverable, environmentally friendly, and low-cost compared with traditional methods. In this paper, the removal of ethyl acetate by non-thermal plasma enhanced with jet flows was carried out in a coaxial dielectric barrier discharge reactor. The influence of the plasma-induced jet flows produced by the discharge of two plasma generators with different arrangements on the spatial flow field was explored. The removal efficiency of ethyl acetate was determined with a series of different experimental parameters: the loading voltage (7–13 kV), the initial concentration of ethyl acetate (100, 500, and 1000 ppm), and the arrangement of the two plasma generators (aligned and diagonal). The results of the numerical simulations and particle image velocimetry tests showed good consistency regarding the influence of the arrangement of the two plasma generators on the spatial flow field. This indicates that the Suzen model was successfully developed for the bulk discharge, and the plasma-induced jet flows generated by the coaxial dielectric barrier discharge could be determined by the direct numerical simulations. The maximal removal efficiency was achieved with a loading voltage of 13 kV, and the removal efficiency of ethyl acetate was greater for the aligned arrangement of plasma generators than for the diagonal arrangement. This work demonstrates for the first time the introduction of the aerodynamics effects of non-thermal plasma into the chemical reaction, providing a completely new way to remove volatile organic compounds.

A novel UV-assisted PEC-MFC system with CeO2/TiO2/ACF catalytic cathode for gas phase VOCs treatment

Emissions of volatile organic compounds (VOCs) air pollutants could worsen air quality and adversely affect human health, thus developing more efficient low-temperature VOCs removal techniques is desired. A novel continuous system integrating UV-assisted photo-electrochemical catalysis with microbial fuel cell (UV-assisted PEC-MFC) has been established for promoting removal of gaseous ethyl acetate or toluene and generating electricity simultaneously. In this system, CeO2/TiO2/ACF catalytic cathode is prepared and used for combination with bio-anode for accelerating cathodic reaction. This UV-assisted PEC-MFC system exhibits an excellent elimination capacity (EC) of ethyl acetate (∼0.39 g/m3, EC: ∼2.52 g/m3/h) or toluene (∼0.29 g/m3, EC: 1.89 g/m3/h) under close-circuit condition. Furthermore, an outstanding elimination capacity (EC: 28.04 g/m3/h) for high concentration toluene (∼4.10 g/m3) removal is obtained after toluene gas passes sequentially through the catalytic cathode then the bio-anode. This way of PEC degradation and biodegradation, avoids inhibition of exoelectrogens activity from toxicity of high concentration toluene. Simultaneously, the cell voltage of UV-assisted PEC-MFC system is stable at 0.11 V (vs. SCE) and 1.452×10−4 kWh is generated from treatment of toluene gas stream in 6 h duration time. The possible mechanism of VOCs removal in this novel system has been proposed and discussed. This study provides new technical basis for treating gaseous pollutants via integrating photo-electrochemical catalysis with electricity generating microbial fuel cell for energy conversion.

Heterotrophic sulfide-oxidizing nitrate-reducing bacteria enables the high performance of integrated autotrophic-heterotrophic denitrification (IAHD) process under high sulfide loading

Micro-aerobic enhancement technology has been developed as an effective tool to enhance simultaneous removal of sulfide, nitrate and organic carbon during the integrated autotrophic-heterotrophic denitrification (IAHD) process under high loading; however, its mechanism of enhancement for functional bacteria remains ambiguous. In this study, we discovered that heterotrophic sulfide-oxidizing nitrate-reducing bacteria (h-soNRB) are responsible for enhancing IAHD performance under micro-aerobic conditions with high sulfide loading. In a continuous IAHD bioreactor, aeration rate of 2.6 mL min−1·L−1 promoted 2 to 4 times higher removal efficiencies of sulfide, nitrate and acetate with an influent sulfide concentration of 18.75 mmol/L. Metagenomic analysis revealed that trace oxygen stimulated the abundance of genes responsible for sulfide oxidation (sqr, glpE, pdo, sox and cysK), which were upregulated by 15.2%–129.9%, and the genes encoding nitrate reductase were up-regulated by 67.4%. The increased acetate removal efficiency was attributed to upregulation of ack, pta and TCA cycle related genes. The h-NRB Pseudomonas, Azoarcus, Thauera and Halomonas were detected and regarded as h-soNRB in our bioreactor. According to Illumina MiSeq sequencing, these genera were absolutely dominant in the micro-aerobic microbial community at relative abundances ranging from 82.72% to 90.84%. The sulfide, nitrate and acetate removal rates of Pseudomonas C27, a typical h-soNRB, were at least 10 times higher under micro-aerobic conditions than under anaerobic conditions. Besides, the sulfur, nitrogen and carbon metabolic network was constructed based on the Pseudomonas C27 genome. The pdo and cysK genes found in this strain may be the most advantageous for autotrophic sulfide oxidizing nitrate reducing bacteria (a-soNRB), which are closely related to the high-efficiency sulfide, nitrate and acetate removal performance under high sulfide concentrations and a limited oxygen supply. In addition, after micro-aerobic cultivation, the anaerobic sulfide loading tolerance of the IAHD bioreactor increased from 18.75 to 37.5 mmol/L with sulfide, nitrate and acetate removal efficiencies increasing 1.5 to 3 times, which suggests that intermittent micro-aeration might be a more economical and efficient regime for high-sulfide IAHD regulation.

Adaptation of Methanosarcina barkeri 227 as acetate scavenger for succinate fermentation by Actinobacillus succinogenes.

Acetate is the main by-product from microbial succinate production. In this study, we performed acetate removal by Methanosarcina barkeri 227 for succinate fermentation by Actinobacillus succinogenes 130Z. The acetoclastic methanogen M. barkeri requires similar environmental factors to A. succinogenes, and the conditions required for co-cultivation were optimized in this study: gas used for anaerobicization, strain adaptation, medium composition, pH adjustment, and inoculation time points. M. barkeri 227 was adapted to acetate for 150days, which accelerated the acetate consumption to 9-fold (from 190 to 1726mmol gDW-1day-1). In the acetate-adapted strain, there was a noticeable increase in transcription of genes required for acetoclastic pathway-satP (acetate transporter), ackA (acetate kinase), cdhA (carbon monoxide dehydrogenase/acetyl-CoA synthase complex), and mtrH (methyl-H4STP:CoM methyltransferase), which was not induced before the adaptation process. The activities of two energy-consuming steps in the pathway-acetate uptake and acetate kinase-increased about 3-fold. This acetate-adapted M. barkeri could be successfully applied to succinate fermentation culture of A. succinogenes, but only after pH adjustment following completion of fermentation. This study suggests the utility of M. barkeri as an acetate scavenger during fermentation for further steps towards genetic and process engineering.