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PubMed2003

Bioreactors for removing methyl bromide following contained fumigations.

Use of methyl bromide (MeBr) as a quarantine, commodity, or structural fumigant is under scrutiny because its release to the atmosphere contributes to the depletion of stratospheric ozone. A closed-system bioreactor consisting of 0.5 L of a growing culture of a previously described bacterium, strain IMB-1, removed MeBr (> 110 micromol L(-1)) from recirculating air. Strain IMB-1 grew slowly to high cell densities in the bioreactor using MeBr as its sole carbon and energy source. Bacterial oxidation of MeBr produced CO2 and hydrobromic acid (HBr), which required continuous neutralization with NaOH for the system to operate effectively. Strain IMB-1 was capable of sustained oxidation of large amounts of MeBr (170 mmol in 46 d). In an open-system bioreactor (10-L fermenter), strain IMB-1 oxidized a continuous supply of MeBr (220 /micromol L(-1) in air). Growth was continuous, and 0.5 mol of MeBr was removed from the air supply in 14 d. The specific rate of MeBr oxidation was 7 x 10(-16) mol cell(-1) h(-1). Bioreactors such as these can therefore be used to remove large quantities of contaminant MeBr, which opens the possibility of biodegradation as a practical means for its disposal.

Air Pollution↗
PubMed2004

Degradation of waste gas containing toluene in an airlift bioreactor.

Suspension microorganisms in an internal-loop airlift bioreactor were utilized to treat waste gas containing toluene. The working volume of the reactor was 35 L, and the biomass concentration was 3 kg/m3. The gas pollutant flowed into the reactor from the bottom; it then transferred from the gas phase to the liquid phase and was degraded by the microorganisms suspended in the liquid phase. The microorganisms were able to degrade 50-90% of the inlet toluene when its concentration was from 0.5 to 10 g/m3, and the superficial gas velocity ranged from 0.15 to 1.23 cm/s. A comprehensive mathematical model was also developed to describe the overall degradation process of toluene in the internal-loop airlift bioreactor. The overall degradation process included gas flow, gas-liquid mass transfer, flow and dispersion of the liquid phase, and microbial kinetics. The hydrodynamic properties including the gas and liquid superficial velocities, the gas holdup, the volumetric mass transfer coefficients of toluene and oxygen, and the microbial kinetics were obtained for this model. The substrate inhibition theory was used to simulate the microorganism growth kinetics, and its kinetic constants were obtained experimentally. The penetration theory was used to predict the volumetric mass transfer coefficient. And the drift-flux theory was used to predict the hydrodynamic properties in each section (riser, gas-liquid separator, downcomer, and bottom) of the airlift bioreactor. The concentration distributions of toluene and oxygen in the airlift bioreactor and the removal efficiency of toluene predicted by the mathematical model agreed well with the experimental data.

Air Movements↗
PubMed2005

Speciation of Co(II) and Ni(II) in anaerobic bioreactors measured by competitive ligand exchange-adsorptive stripping voltammetry.

Competitive ligand exchange-adsorptive stripping voltammetry is applied to speciation analysis of dissolved Ni(II) and Co(II) in an anaerobic bioreactor and similar batch media. Co and Ni speciation in these media can be measured down to concentration levels of ca. 1 nM. Sulfide interference is avoided via removal as H2S. In methanogenic bioreactors, up to 95% of the dissolved Co and Ni is present in strongly bound forms, with complex stabilities > or =10(8)-10(9) and 10(7)-10(8) mol(-1) L, respectively. In effluent from sulfate-reducing bioreactors, Co is also found to be present in a strongly bound form, and up to micromolar levels of strongly complexing excess ligand was detected. The predominant presence of Co and Ni in strong complexes, with concomitant low free dissolved concentrations, is significant for limitation by these elements in anaerobic bioreactors.

Anaerobiosis↗
PubMed2006

Gaseous hexane biodegradation by Fusarium solani in two liquid phase packed-bed and stirred-tank bioreactors.

Biofiltration of hydrophobic volatile pollutants is intrinsically limited by poor transfer of the pollutants from the gaseous to the liquid biotic phase, where biodegradation occurs. This study was conducted to evaluate the potential of silicone oil for enhancing the transport and subsequent biodegradation of hexane by the fungus Fusarium solani in various bioreactor configurations. Silicone oil was first selected among various solvents for its biocompatibility, nonbiodegradability, and good partitioning properties toward hexane. In batch tests, the use of silicone oil improved hexane specific biodegradation by approximately 60%. Subsequent biodegradation experiments were conducted in stirred-tank (1.5 L) and packed-bed (2.5 L) bioreactors fed with a constant gaseous hexane load of 180 g x m(-3)(reactor) x h(-1) and operated for 12 and 40 days, respectively. In the stirred reactors, the maximum hexane elimination capacity (EC) increased from 50 g x m(-3)(reactor) x h(-1) (removal efficiency, RE of 28%) in the control not supplied with silicone oil to 120 g x m(-3)(reactor) x h(-1) in the biphasic system (67% RE). In the packed-bed bioreactors, the maximum EC ranged from 110 (50% RE) to 180 g x m(-3)(reactor) x h(-1) (> 90% RE) in the control and two-liquid-phase systems, respectively. These results represent, to the best of our knowledge, the first reported case of fungi use in a two-liquid-phase bioreactor and the highest hexane removal capacities so far reported in biofilters.

Biodegradation, Environmental↗
PubMed2001

Sotolone production by hairy root cultures of Trigonella foenum-graecum in airlift with mesh bioreactors.

3-Hydroxy-4,5-dimethyl-2(5H)-furanone (sotolone) and 3-amino-4,5-dimethyl-2(5H)-furanone, the postulated precursor of sotolone, were detected in hairy root cultures of Trigonella foenum-graecum (fenugreek) by GC-MS. The hairy root cultures in both conical flasks and airlift with mesh bioreactors were achieved from hypocotyl of seedling by infection with Agrobacterium rhizogenes. In flasks, the mathematical relationship between hairy root growth and conductivity was established and afterward used to evaluate the biomass evolution in bioreactor cultures due to the difficulty of obtaining direct biomass samples from the bioreactor. The GC-MS analyses of ethanolic extracts from hairy roots revealed the presence of two important compounds: sotolone (1.2% of the volatile fraction) and 3-amino-4,5-dimethyl-2(5H)-furanone (17% of the volatile fraction). These results point out that biotechnological production of sotolone in bioreactors is possible. Additionally, these hairy root cultures offer, for the first time, an excellent biological model to study the biosynthetic pathway of sotolone in fenugreek.

Bioreactors↗
PubMed2003

Astragaloside IV and polysaccharide production by hairy roots of Astragalus membranaceus in bioreactors.

Hairy roots of Astragalus membranaceus were grown in bioreactors up to 30 l for 20 d. Cultures from a 30 l airlift bioreactor gave 11.5 g l dry wt with 1.4 mg g(-1) astragaloside IV, similar to cultures from 250 ml and 1 l flasks, but greater than yields from a 10 l bioreactor (dry wt 9.4 g l(-1), astragaloside IV 0.9 mg g(-1)). Polysaccharide yields were similar amongst the different bioreactors (range 25-32 mg g(-1)). The active constituent content of the cells approached that of plant extracts, indicating that large scale hairy root cultures of A. membranaceus has the potential to provide an alternative to plant crops without compromising yield or pharmacological potential.

Astragalus propinquus↗
PubMed2004

Light sensitivity of Bifidobacterium longum in bioreactor cultivations.

Bifidobacteria are gaining commercial significance due to their probiotic properties. However, little is still known about the production of these bacteria and their behavior in bioreactors. Two Bifidobacterium longum strains were sensitive to light when grown in a transparent (glass) bioreactor under microaerophilic growth conditions (i.e. no gases added and slow mixing). The sensitivity was less clear the more anaerobic the initial conditions were. In a darkened bioreactor in microaerophilic conditions, the two strains grew with maximum specific growth rates of 0.36 h(-1) and 0.48 h(-1). In an illuminated bioreactor neither strain grew. In comparison, Lactobacillus reuteri was not sensitive to light under the same conditions.

Bifidobacterium↗
PubMed2004

Biofilm population dynamics in a trickle-bed bioreactor used for the biodegradation of aromatic hydrocarbons from waste gas under transient conditions.

The dynamics of a multispecies biofilm population in a laboratory-scale trickle-bed bioreactor for the treatment of waste gas was examined. The model pollutant was a VOC-mixture of polyalkylated benzenes called Solvesso 100. Fluorescence in-situ hybridization (FISH) was applied in order to characterise the population composition. The bioreactor was operated under transient conditions by applying pollutant concentration shifts and a starvation phase. Only about 10% of the biofilm mass were cells, the rest consisted of extracellular polymeric substances (EPS). The average fraction of Solvesso 100-degrading cells during pollutant supply periods was less than 10%. About 60% of the cells were saprophytes and about 30% were inactive cells. During pollutant concentration shift experiments, the bioreactor performance adapted within a few hours. The biofilm population exhibited a dependency upon the direction of the shifts. The population reacted within days after a shift-down and within weeks after a shift-up. The pollutant-degraders reacted significantly faster compared to the other cells. During the long-term starvation phase, a shift of the population composition took place. However, this change of composition as well as the degree of metabolic activity was completely reversible. A direct correlation between the biodegradation rate of the bioreactor and the number of pollutant-degrading cells present in the biofilm could not be obtained due to insufficient experimental evidence.

Biodegradation, Environmental↗
PubMed1997

Comparison between the evaluation of bacterial regrowth capability in a turbidimeter and biodegradable dissolved organic carbon bioreactor measurements in water.

In recent years, two different approaches to the study of biodegradable organic matter in distribution systems have been followed. The assimilable organic carbon (AOC) indicates the portion of the dissolved organic matter used by bacteria and converted to biomass, which is directly measured as total bacteria, active bacteria or colony-forming units and indirectly as ATP or increase in turbidity. In contrast, the biodegradable dissolved organic carbon (BDOC) is the portion of the dissolved organic carbon that can be mineralized by heterotrophic microorganisms, and it is measured as the difference between the inflow and the outflow of a bioreactor. In this study, at different steps in a water treatment plant, the bacterial regrowth capability was determined by the AOC method that measures the maximum growth rate by using a computerized Monitek turbidimeter. The BDOC was determined using a plug flow bioreactor. Measurements of colony-forming units and total organic carbon (TOC) evolution in a turbidimeter and of colony-forming units at the inflow/outflow of the bioreactor were also performed, calculating at all sampling points the coefficient yield (Y = cfu/delta TOC) in both systems. The correlations between the results from the bioreactor and turbidimeter have been calculated; a high correlation level was observed between BDOC values and all the other parameters, except for Y calculated from bacterial suspension measured in the turbidimeter.

Bacteria↗
PubMed2002

Production of paclitaxel and baccatin III in a 20-L airlift bioreactor by a cell suspension of Taxus wallichiana.

A cell suspension culture of Taxus wallichiana (Himalayan Yew) was grown in shake flasks and a 20-L airlift bioreactor running for 28 days in a batch mode, and its capacity to accumulate paclitaxel and baccatin III was measured. When both culture types were in the highest productive state (from day 24 to day 28), there was a greater accumulation of paclitaxel and baccatin III in the bioreactor culture than in the shake flask culture (factor of 2.0 and 1.2, respectively). These increases in paclitaxel and baccatin III production cannot be related to the difference observed between the growth rates of both cultures, because when the bioreactor culture was at maximum productivity, its cell biomass, expressed in g L(-1) of dry weight, was similar to that obtained in the shake flask culture. It seems that these improvements were mainly due to adequate aeration and mixing of the culture in the bioreactor. The maximum yield observed for paclitaxel (20.84 mg x L(-1) day 24) and baccatin III (25.67 mg x L(-1) day 28) represents a productivity of 0.90 mg x L(-1) d(-1) and 0.93 mg x L(-1) x d(-1) respectively.

Air↗
PubMed2004

Bioreactor-based bone tissue engineering: the influence of dynamic flow on osteoblast phenotypic expression and matrix mineralization.

An important issue in tissue engineering concerns the possibility of limited tissue ingrowth in tissue-engineered constructs because of insufficient nutrient transport. We report a dynamic flow culture system using high-aspect-ratio vessel rotating bioreactors and 3D scaffolds for culturing rat calvarial osteoblast cells. 3D scaffolds were designed by mixing lighter-than-water (density, <1g/ml) and heavier-than-water (density, >1g/ml) microspheres of 85:15 poly(lactide-co-glycolide). We quantified the rate of 3D flow through the scaffolds by using a particle-tracking system, and the results suggest that motion trajectories and, therefore, the flow velocity around and through scaffolds in rotating bioreactors can be manipulated by varying the ratio of heavier-than-water to lighter-than-water microspheres. When rat primary calvarial cells were cultured on the scaffolds in bioreactors for 7 days, the 3D dynamic flow environment affected bone cell distribution and enhanced cell phenotypic expression and mineralized matrix synthesis within tissue-engineered constructs compared with static conditions. These studies provide a foundation for exploring the effects of dynamic flow on osteoblast function and provide important insight into the design and optimization of 3D scaffolds suitable in bioreactors for in vitro tissue engineering of bone.

Alkaline Phosphatase↗
PubMed2004

Molecular analysis of the community structure of nitrifying bacteria in a continuous-flow bioreactor.

We herein report the diversity and relative abundance of chemolithotrophic nitrifying bacteria in a continuous-flow bioreactor using 16S-ribosomal RNA quantitative dot-blot hybridizations. About 14.9% of the total bacterial population, determined by epifluorescence microscopy in the bioreactor suspended phase, was represented by nitrifying bacteria. Of this fraction, ammonia- and nitrite-oxidizing bacteria accounted for 10% and 90%, respectively, the latter group being mostly Nitrospira-like. On the other hand, the nitrifiers adhesion/colonization capacity on polyethylene surfaces as evaluated by scanning electron microscopy and hybridizations analyses was 12.6% of the total bacterial community adhered. Finally, in spite of the relatively small contribution of nitrifiers to the total bacterial abundance in the bioreactor, we determined a mean ammonia removal rate of 170.48 +/- 8.29 mg N l(-1) d(-1); thus, the low percentage of ammonia-oxidizing bacteria, was not limiting the bioreactor performance.

Ammonia↗
PubMed2006

Electrocoagulation combined with the use of an intermittently aerating bioreactor to enhance phosphorus removal.

Biological Oxygen Demand (BOD), nitrogen, and phosphorus were treated with the use of an intermittently aerating bioreactor combined with electrocoagulation. Experiments consisting of batch reactor tests were conducted to identify the most efficient electrode material and the best condition for electrolysis so that the current density would not impede the biological treatment. The operating conditions needed when using an intermittently aerating bioreactor combined with electrocoagulation to enhance phosphorus removal were also identified. Iron was found to be more efficient than aluminum as an electrode material in terms of electricity requirement. When electrocoagulation was conducted and an intermittently aerating bioreactor was used, the electrolysis of the iron electrode in the aerobic stage was observed to be more favorable compared to continuous electrolysis. Sludge rise occurred at the current density of 5.7 mA cm(-2), and lysis of cell at 11.2 mA cm(-2). The applicable current density was found to be less than 4 mA cm(-2). Based on the results of this study, it can be concluded that the use of an intermittently aerating bioreactor combined with electrocoagulation enhances phosphorus removal in sewage treatment plants.

Aluminum↗
PubMed1995

Pilot-scale demonstration of a two-stage methanotrophic bioreactor for biodegradation of trichloroethylene in groundwater.

A two-stage methanotrophic bioreactor system was developed for remediation of water contaminated with TCE and other chlorinated, volatile, aliphatic hydrocarbons. The first stage of the reactor was a suspended-growth culture vessel using a bubbleless methane-transfer device. The second stage was a plug-flow bioreactor supplied with contaminated groundwater and cell suspension from the culture vessel. The test objectives were to determine the applicability of microbial culture conditions reported in the literature for continuous, pilot-scale TCE treatment; the technical feasibility of plug-flow bioreactor design for treatment of TCE; and the projected economic competitiveness of the technology considering the cost of methane for growth of methanotrophs. The methanotrophic organism used in the study was Methylosinus trichosporium OB3b. Information on system operation was obtained in bench tests prior to conducting the pilot tests. In bench- and pilot-scale tests, variability in the degree of TCE degradation and difficulty in maintaining the microbial culture activity led to short periods of satisfactory biotreatment. Further development of the microbial culture system will be required for long-term operation. During transient periods of high TCE degradation activity, the bioreactor concept proved feasible by exhibiting both a high degree of TCE biodegradation (typically about 90% at influent TCE concentrations of 0.5-4 ppm) and a close approximation to first-order reactor kinetics throughout the length of the reactor. Actual methane usage in the pilot-scale reactor resulted in projected methane costs of $0.33 per 1000 gallons of water treated. This cost theoretically would be reduced by system modifications. The theoretical minimum methane cost was approximately $0.05 per 1000 gallons.

Biodegradation, Environmental↗
PubMed2004

Landfill leachate treatment by yeast and bacteria based membrane bioreactors.

Biological treatment of medium-age landfill leachate was investigated on a membrane bioreactor. The experiments were conducted in two 5-L reactors with immersed hollow fiber microfiltration membranes. One reactor was operated with a mixed bacterial culture termed as bacteria based membrane bioreactor (BMBR) while the other with mixed yeast culture termed as yeast based membrane bioreactor (YMBR). The leachate was characterized with a chemical oxygen demand (COD) concentration of 7000-9000mg/L, biochemical oxygen demand (5 days) to chemical oxygen demand ratio (BOD5/COD) of 0.35-0.45 and total Kjeldahl nitrogen (TKN) of 1800-2000mg/L. The performance was assessed with and without ammonia stripping. In both the reactors, the average COD and TKN removal efficiency without ammonia stripping ranged between 52-66 and 14-28%, respectively. The performance of both the membrane bioreactors improved with ammonia stripping in terms of both COD (72-76%) and TKN (82-89%) removal efficiency. Though, the difference in the performance of the BMBR and YMBR was not significant in terms of COD removal, the YMBR showed better removal efficiency in terms of BOD5. The molecular weight cut-off showed that the degradation pathway of the leachate by bacterial and yeast are different. In regard to membrane fouling, the YMBR showed better performance with lower trans-membrane pressure as well as longer operating time. This superior performance of the YMBR could be due to the structure of yeast cells which are larger in size as well as reduced soluble extracellular polymeric substances (EPS) production, which are the main cause of membrane biofouling.

Bacteria↗
PubMedDate not supplied

Time course of primary liver cell reorganization in three-dimensional high-density bioreactors for extracorporeal liver support: an immunohistochemical and ultrastructural study.

To enable extracorporeal liver support based on the use of primary liver cells, culture models supporting the maintenance of cell integrity and function in vitro are required. In this study the cell organization and ultrastructure of primary porcine hepatocytes cocultured with nonparenchymal cells in three-dimensional high-density bioreactors were analyzed after 10, 20, and 30 days of culture by immunohistochemistry and transmission electron microscopy. Biochemical data showed that metabolic activity of the cells in the system was relatively stable over at least 20 days. Immunohistochemical studies were performed in comparison with donor organ biopsies. They showed that hepatocytes and nonparenchymal cells reaggregated in bioreactors, forming structures partly resembling natural liver parenchyma. Bile duct-like structures characterized by cytokeratin 7 (CK-7) immunoreactivity (IR) were regularly detected. Nonparenchymal cells (vimentin IR) formed sinusoidal-like structures within parenchymal cell aggregates. Proliferative activity (Ki-67 IR) increased over time. The detection of collagen I and laminin indicated the production of extracellular matrix components within bioreactors. The results showed that primary liver cell reorganization and long-term maintenance of their differentiated state were achieved within the bioreactors The findings on cell proliferation indicated that the culture model is also of interest for further in vitro studies on cell regeneration and tissue formation.

Adaptation, Physiological↗
PubMedDate not supplied

Development of a closed bioreactor system for culture of tissue-engineered skin at an air-liquid interface.

A bioreactor has been developed for the production of tissue-engineered skin at an air-liquid interface for clinical and experimental use. In this closed system, scaffold and bioreactor sterilization, cell seeding, and medium perfusion were all performed with a peristaltic pump. Natural and synthetic dermal substitutes were seeded directly with skin cells without opening the bioreactor and fed either by continuous medium perfusion or by batch-feed. The system was validated by monoculture of human dermal fibroblasts and keratinocytes and the coculture of both cell types in acellular human dermis, Azowipes, electrospun polystyrene, and an electrospun composite of polystyrene and poly-DL-lactide fibers. A comparison was made of culture at an air-liquid interface versus submerged culture and of medium change by continuous perfusion versus batch-feed. Fibroblast and endothelial cells showed greater viability under submerged rather than air-liquid conditions whereas keratinocytes favored culture at an air-liquid interface as did cocultured keratinocytes and fibroblasts. Total cellular viability for reconstructed skin with keratinocytes and fibroblasts was greatest with continuous perfusion rather than batch-feed and with electrospun scaffolds compared with acellular human dermis. The bioreactor could also be easily configured to give replicate small areas for experimental use or one continuous area of construct for clinical use.

Air↗
PubMed2003

Perfusion bioreactor for vascular tissue engineering with capacities for longitudinal stretch.

Arterial growth during embryonic vascular development is associated with longitudinal strain. The longitudinal strain is an important element of the embryonic vascular mechanical environment (EVME). Thus, a perfusion bioreactor for vascular tissue engineered constructs must include the functional capacity for longitudinal strain. To accomplish this goal, a perfusion bioreactor with the capacity for longitudinal strain was developed. The bioreactor includes two media perfusion systems: one for the inside perfusion and one for the outside perfusion of the cardiovascular engineered tubular construct (CETC). The watertight perfusion chamber allows periodic changing of longitudinal strain of the construct during mechanical conditioning. The range of the longitudinal strain is 0% to 200%. The biomechanical properties of the CETC are controlled by a pressure transducer and a digital TV camera. The pressure transducer and TV camera are connected to a computer. This allows the recording of a relationship between the radius of the VTEG and pressure in both static and dynamic regimens. This bioreactor can perform biomechanical conditioning with longitudinal strain.

Animals↗