High-pressure Bioreactor Research Articles

Stimulated Organic Carbon Cycling and Microbial Community Shift Driven by a Simulated Cold-Seep Eruption.

ABSTRACTCold seeps are a major methane source in marine systems, and microbe-mediated anaerobic oxidation of methane (AOM) serves as an effective barrier for preventing methane emissions from sediment to water. However, how the periodic eruption of cold seeps drives the microbial community shift and further affects carbon cycling has been largely neglected, mainly due to the technical challenge of analyzing the in situ communities undergoing such geological events. Using a continuously running high-pressure bioreactor to simulate these events, we found that under the condition of simulated eruptions, the abundance of AOM-related species decreased, and some methane was oxidized to methyl compounds to feed heterotrophs. The methanogenic archaeon Methanolobus replaced ANME-2a as the dominant archaeal group; moreover, the levels of methylotrophic bacteria, such as Pseudomonas, Halomonas, and Methylobacter, quickly increased, while those of sulfate-reducing bacteria decreased. According to the genomic analysis, Methylobacter played an important role in incomplete methane oxidation during eruptions; this process was catalyzed by the genes pmoABC under anaerobic conditions when the methane pressure was high, possibly generating organic carbon. Additionally, the findings showed that methyl compounds can also be released to the environment during methanogenesis and AOM under eruption conditions when the methane pressure is high.

Direct and Indirect Effects of Increased CO2 Partial Pressure on the Bioenergetics of Syntrophic Propionate and Butyrate Conversion.

Simultaneous digestion and in situ biogas upgrading in high-pressure bioreactors will result in elevated CO2 partial pressure (pCO2). With the concomitant increase in dissolved CO2, microbial conversion processes may be affected beyond the impact of increased acidity. Elevated pCO2 was reported to affect the kinetics and thermodynamics of biochemical conversions because CO2 is an intermediate and end-product of the digestion process and modifies the carbonate equilibrium. Our results showed that increasing pCO2 from 0.3 to 8 bar in lab-scale batch reactors decreased the maximum substrate utilization rate (rsmax) for both syntrophic propionate and butyrate oxidation. These kinetic limitations are linked to an increased overall Gibbs free energy change (ΔGOverall) and a potential biochemical energy redistribution among syntrophic partners, which showed interdependence with hydrogen partial pressure (pH2). The bioenergetics analysis identified a moderate, direct impact of elevated pCO2 on propionate oxidation and a pH-mediated effect on butyrate oxidation. These constraints, combined with physiological limitations on growth exerted by increased acidity and inhibition due to higher concentrations of undissociated volatile fatty acids, help to explain the observed phenomena. Overall, this investigation sheds light on the role of elevated pCO2 in delicate biochemical syntrophic conversions by connecting kinetic, bioenergetic, and physiological effects.

Biodegradation of isopropanol and acetone under denitrifying conditions by Thauera sp. TK001 for nitrate-mediated microbially enhanced oil recovery

Amendment of reservoir fluid with injected substrates can enhance the growth and activity of microbes. The present study used isopropyl alcohol (IPA) or acetone to enhance the indigenous anaerobic nitrate-reducing bacterium Thauera sp. TK001. The strain was able to grow on IPA or acetone and nitrate. To monitor effects of strain TK001 on oil recovery, sand-packed columns containing heavy oil were flooded with minimal medium at atmospheric or high (400psi) pressure. Bioreactors were then inoculated with 0.5 pore volume (PV) of minimal medium containing Thauera sp. TK001 with 25mM of acetone or 22.2mM of IPA with or without 80mM nitrate. Incubation without flow for two weeks and subsequent injection with minimal medium gave an additional 17.0±6.7% of residual oil in place (ROIP) from low-pressure bioreactors and an additional 18.3% of ROIP from the high-pressure bioreactors. These results indicate that acetone or IPA, which are commonly used organic solvents, are good substrates for nitrate-mediated microbial enhanced oil recovery (MEOR), comparable to glucose, acetate or molasses, tested previously. This technology may be used for coupling biodegradation of IPA and/or acetone in waste streams to MEOR where these waste streams are generated in close proximity to an oil field.

Microbially Enhanced Oil Recovery by Sequential Injection of Light Hydrocarbon and Nitrate in Low- And High-Pressure Bioreactors.

Microbially enhanced oil recovery (MEOR) often involves injection of aqueous molasses and nitrate to stimulate resident or introduced bacteria. Use of light oil components like toluene, as electron donor for nitrate-reducing bacteria (NRB), offers advantages but at 1-2 mM toluene is limiting in many heavy oils. Because addition of toluene to the oil increased reduction of nitrate by NRB, we propose an MEOR technology, in which water amended with light hydrocarbon below the solubility limit (5.6 mM for toluene) is injected to improve the nitrate reduction capacity of the oil along the water flow path, followed by injection of nitrate, other nutrients (e.g., phosphate) and a consortium of NRB, if necessary. Hydrocarbon- and nitrate-mediated MEOR was tested in low- and high-pressure, water-wet sandpack bioreactors with 0.5 pore volumes of residual oil in place (ROIP). Compared to control bioreactors, those with 11-12 mM of toluene in the oil (gained by direct addition or by aqueous injection) and 80 mM of nitrate in the aqueous phase produced 16.5 ± 4.4% of additional ROIP (N = 10). Because toluene is a cheap commodity chemical, HN-MEOR has the potential to be a cost-effective method for additional oil production even in the current low oil price environment.

Advances in the Surgical Management of Articular Cartilage Defects: Autologous Chondrocyte Implantation Techniques in the Pipeline.

Objective:The purpose of this review is to gain insight into the latest methods of articular cartilage implantation (ACI) and to detail where they are in the Food and Drug Administration approval and regulatory process.Design:A PubMed search was performed using the phrase “Autologous Chondrocyte Implantation” alone and with the words second generation and third generation. Additionally, clinicaltrials.gov was searched for the names of the seven specific procedures and the parent company websites were referenced.Results:Two-Stage Techniques: BioCart II uses a FGF2v1 culture and a fibrinogen, thrombin matrix, whereas Hyalograft-C uses a Hyaff 11 matrix. MACI uses a collagen I/III matrix. Cartipatch consists of an agarose-alginate hydrogel. Neocart uses a high-pressure bioreactor for culturing with a type I collagen matrix. ChondroCelect makes use of a gene expression analysis to predict chondrocyte proliferation and has demonstrated significant clinical improvement, but failed to show superiority to microfracture in a phase III trial. One Step Technique: CAIS is an ACI procedure where harvested cartilage is minced and implanted into a matrix for defect filling.Conclusion:As full thickness defects in articular cartilage continue to pose a challenge to treat, new methods of repair are being researched. Later generation ACI has been developed to address the prevalence of fibrocartilage with microfracture and the complications associated with the periosteal flap of first generation ACI such as periosteal hypertrophy. The procedures and products reviewed here represent advances in tissue engineering, scaffolds and autologous chondrocyte culturing that may hold promise in our quest to alter the natural history of symptomatic chondral disease.

Enrichment of a microbial community performing anaerobic oxidation of methane in a continuous high-pressure bioreactor

BackgroundAnaerobic oxidation of methane coupled to sulphate reduction (SR-AOM) prevents more than 90% of the oceanic methane emission to the atmosphere. In a previous study, we demonstrated that the high methane pressure (1, 4.5, and 8 MPa) stimulated in vitro SR-AOM activity. However, the information on the effect of high-pressure on the microbial community structure and architecture was still lacking.ResultsIn this study we analysed the long-term enrichment (286 days) of this microbial community, which was mediating SR-AOM in a continuous high-pressure bioreactor. 99.7% of the total biovolume represented cells in the form of small aggregates (diameter less then 15 μm). An increase of the total biovolume was observed (2.5 times). After 286 days, the ANME-2 (anaerobic methanotrophic archaea subgroup 2) and SRB (sulphate reducing bacteria) increased with a factor 12.5 and 8.4, respectively.ConclusionThis paper reports a net biomass growth of communities involved in SR-AOM, incubated at high-pressure.

Stimulation of in vitro anaerobic oxidation of methane rate in a continuous high-pressure bioreactor

Anaerobic oxidation of methane coupled to sulphate reduction (SR-AOM) prevents oceanic methane emissions and is considered as a major environmental process in the deep-sea sediments. To stimulate in vitro SR-AOM activity, we designed a (continuous) high-pressure bioreactor system. Fed-batch mode incubations showed that the elevated methane pressure stimulated SR-AOM activity: when the methane pressure increased from 1 to 4.5 to 8 MPa, the initial SR-AOM activity increased from 3.46 to 8.64 to 9.22 μmol sulphide production/ g dw/day; the apparent affinity ( K m) for methane was 37 mM. However, in each fed-batch mode incubation, there was an inhibitory effect observed after 2 days, probably due to the accumulation of sulphide and the increase of pH. When the reactor was operated in a continuous mode, the SR-AOM activity was constantly increasing within 18 days at both 1 and 8 MPa pressures.

Tissue engineered cartilage development in a perfused high pressure bioreactor

The growth of engineered cartilage tissue in vitro is often impaired by the problem of insufficient oxygen and nutrient supply to cells seeded in 3D constructs. Despite its central role in controlling most cell functions, the scaffolding material has generally been thought of only as a transport barrier and its potential active role in controlling oxygen uptake has never been addressed. In this work the role of cell–material interaction on oxygen metabolism in 3D in vitro cultures was surveyed. To this aim bovine chondrocytes, at a cell density of 400,000 and 4,000,000 cells/mL, respectively, were seeded in collagen type I and in agarose, while keeping all other culture conditions constant. A unidirectional oxygen gradient was induced in the culture through the application of a “sandwich” model and the oxygen concentration at the pericellular level was measured by phosphorescence quenching microscopy. Results show that the oxygen consumption rate is two-fold higher in agarose than in collagen, which indicates that the nature of the material strongly influences cell metabolic behaviour. Moreover, since different oxygen consumption rates are linked to different cell biosynthetic activity, our findings will prove beyond any doubt the active role played by materials in tissue regeneration.

Aerobic treatment of inhibitory wastewater using a high-pressure bioreactor with membrane separation

Wastewater high in phenolic content (948 mg/l) and dissolved solids (5.4 g/l) had to be treated to remove most of the organic material and toxic compounds. A laboratory scale High Pressure (3 bar) Bioreactor (HPB) was developed and operated to treat the wastewater using a ceramic ultra filtration membrane as biomass separator. The performance of the system was compared to a normal activated sludge plant (ASP) using sludge settling for separation. The HPB was more stable than the ASP, which twice became unstable with a resulting biomass loss. Both reactors removed 90% of the chemical oxygen demand (COD) loading, reducing the phenol concentration below 20 mg/l. The maximum COD removal rate of the HPB was 28 kg/m3.d compared to 15 kg/m3.d of the ASP, while the HPB achieved 16-32 times better oxygen transfer than the ASP. It was concluded that the HPB was the preferred treatment system compared to the ASP, when treating high strength inhibitory wastewaters, due to its stable operating performance and high COD removal rate.