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At least 217 records · Page 12Linked to original sources
PubMed2004

Perchlorate removal in sand and plastic media bioreactors.

The treatment of perchlorate-contaminated groundwater was examined using two side-by-side pilot-scale fixed-bed bioreactors packed with sand or plastic media, and bioaugmented with the perchlorate-degrading bacterium Dechlorosoma sp. KJ. Groundwater containing perchlorate (77microg/L), nitrate (4mg-NO(3)/L), and dissolved oxygen (7.5mg/L) was amended with a carbon source (acetic acid) and nutrients (ammonium phosphate). Perchlorate was completely removed (<4microg/L) in the sand medium bioreactor at flow rates of 0.063-0.126L/s (1-2gpm or hydraulic loading rate of 0.34-0.68L/m(2)s) and in the plastic medium reactor at flow rates of <0.063L/s. Acetate in the sand reactor was removed from 43+/-8 to 13+/-8mg/L (after day 100), and nitrate was completely removed in the reactor (except day 159). A regular (weekly) backwashing cycle was necessary to achieve consistent reactor performance and avoid short-circuiting in the reactors. For example, the sand reactor detention time was 18min (hydraulic loading rate of 0.68L/m(2)s) immediately after backwashing, but it decreased to only 10min 1 week later. In the plastic medium bioreactor, the relative changes in detention time due to backwashing were smaller, typically changing from 60min before backwashing to 70min after backwashing. We found that detention times necessary for complete perchlorate removal were more typical of those expected for mixed cultures (10-18min) than those for the pure culture (<1min) reported in our previous laboratory studies. Analysis of intra-column perchlorate profiles revealed that there was simultaneous removal of dissolved oxygen, nitrate, and perchlorate, and that oxygen and nitrate removal was always complete prior to complete perchlorate removal. This study demonstrated for the first time in a pilot-scale system, that with regular backwashing cycles, fixed-bed bioreactors could be used to remove perchlorate in groundwater to a suitable level for drinking water.

Bacteria↗
PubMed2005

Gas-inducible product gene expression in bioreactors.

Inducible transgene expression technologies are of unmatched potential for biopharmaceutical manufacturing of unstable, growth-impairing and cytotoxic proteins as well as conditional metabolic engineering to improve desired cell phenotypes. Currently available transgene dosing modalities which rely on physical parameters or small-molecule drugs for transgene fine-tuning compromise downstream processing and/or are difficult to implement technologically. The recently designed gas-inducible acetaldehyde-inducible regulation (AIR) technology takes advantage of gaseous acetaldehyde to modulate product gene expression levels. At regulation effective concentrations gaseous acetaldehyde is physiologically inert and approved as food additive by the Federal Drug Administration (FDA). During standard bioreactor operation, gaseous acetaldehyde could simply be administered using standard/existing gas supply tubing and eventually eliminated by stripping with inducer-free air. We have determined key parameters controlling acetaldehyde transfer in three types of bioreactors and designed a mass balance-based model for optimal product gene expression fine-tuning using gaseous acetaldehyde. Operating a standard stirred-tank bioreactor set-up at 10 L scale we have validated AIR technology using CHO-K1-derived serum-free suspension cultures transgenic for gas-inducible production of human interferon-beta (IFN-beta). Gaseous acetaldehyde-inducible IFN-beta production management was fully reversible while maintaining cell viability at over 95% during the entire process. Compatible with standard bioreactor design and downstream processing procedures AIR-based technology will foster novel opportunities for pilot and large-scale manufacturing of difficult-to-produce protein pharmaceuticals.

Acetaldehyde↗
PubMed2001

Monitoring of cell viability and cell growth in a hollow-fiber bioreactor by use of the dye Alamar Blue.

We describe a method for monitoring cell proliferation in a small-scale hollow-fiber bioreactor (culture volume: 1 ml) by use of the Alamar Blue dye. Alamar Blue is a non-fluorescent compound, which yields a fluorescent product after reduction, e.g. by living cells. In contrast to the MTT-assay, the Alamar Blue assay does not lead to cell death. However, when not removed from the cells, the Alamar Blue dye shows a reversible, time- and concentration-dependent growth inhibition as observed for the leukemic cell lines CCRF-CEM, HL-60 and REH. When applied in the medium compartment of a hollow-fiber bioreactor system, the dye is delivered to the cells across the hollow-fiber membrane, reduced by the cells and released from the cell into the medium compartment back again. Thus, fluorescence intensity can be measured in medium samples reflecting growth of the cells in the cell compartment. This procedure offers several advantages. First, exposure of the cells to the dye can be reduced compared to conventional culture in plates. Second, handling steps are minimized since no sample of the cells needs to be taken for readout. Moreover, for the exchange of medium, a centrifugation step can be avoided and the cells can be cultivated further. Third, the method allows discriminating between cell densities of 10(5), 10(6) and 10(7) of proliferating HL-60 cells cultivated in the cell compartment of the bioreactor. Measurement of fluorescence in the medium compartment is more sensitive compared to glucose or lactate measurement for cell counts below 10(6) cells/ml, in particular. We conclude that the Alamar Blue-assay combined with a hollow-fiber bioreactor offers distinct advantages for the non-invasive monitoring of cell viability and proliferation in a closed system.

Bioreactors↗
PubMed2002

Dialysis-based bioreactor systems for the production of monoclonal antibodies--alternatives to ascites production in mice.

Two commercially available bioreactor systems, CELLine and miniPERM, were evaluated for their ability to support the production of monoclonal antibody (mAb) from a variety of murine hybridoma cell lines. Production and purity of mAbs were compared between the two systems and with mouse ascites tumour fluid generation. The quality and purity of the mAb generated by each method was analysed on SDS-PAGE gels and the antibody immunoreactivity in each case was quantified by indirect ELISA tests. The relative benefits of conventional growth medium (Dulbecco's modified Eagle's media, DMEM) and serum-free medium (hybridoma serum-free media, H-SFM) using the miniPERM system were also analysed, in terms of the amount of antibody produced, cell concentration and specific antibody titre. In all cases, the CELLine units tested gave higher protein concentrations compared to the miniPERM system under the same conditions (means and 95% confidence limits are 4.2+/-0.8 and 2.1+/-0.8 mg/ml, respectively), yet the miniPERM system yielded greater total amounts over a similar culture period (428.7+/-243.3 mg compared to 183.3+/-100.9 mg in the CL-350 CELLine unit). When defined by specific ELISA titre, both bioreactor systems yielded mAb levels that compared favourably with those derived from ascites. In addition, SDS-PAGE analysis indicated that the bioreactor antibody product was relatively free of contaminating protein, whereas ascites tumour fluid preparations displayed significant levels of extraneous protein. This study has shown that both bioreactor systems are acceptable in vitro alternatives to the in vivo production of mAbs in mice.

Animals↗
PubMed2000

Industrial wastewater bioreactors: sources of novel microorganisms for biotechnology.

Microorganisms exist in nature as members of complex, mixed communities. The microbial communities in industrial wastewater bioreactors can be used as model systems to study the evolution of new metabolic pathways in natural ecosystems. The evolution of microbial metabolic capability in these bioreactors is presumably analogous to phenomena that occur in natural ecosystems. The microorganisms in these bioreactors compete for different carbon sources and constantly have to evolve new metabolic capabilities for survival. Thus, industrial bioreactors should be a rich source of novel biocatalysts.

Bacteria↗
PubMed2000

High level benzodiazepine and ammonia clearance by flat membrane bioreactors with porcine liver cells.

The onset of hepatic encephalopathy is a multifactorial process in which endogenous benzodiazepines and hyperammonemia play a pivotal role. The treatment of comatose states in liver failure is one of the major functions of a bioartificial liver. A controlled study demonstrating the capacity of a large scale bioartificial liver to detoxify benzodiazepines could be a crucial prerequisite to break this circle of events leading to coma. The aim of this study was therefore to expose the bioreactor to high levels of benzodiazepines and ammonia for evaluation of its detoxifying capacity. We have developed a novel and unique device reconstructing the plate architecture of the liver. Porcine hepatocytes were co-cultured with non-parenchymal cells. We investigated benzodiazepine metabolism using diazepam as model drug. The bioreactor was also loaded with high levels of ammonia and ammonia clearance as well as urea secretion with ammonia challenge were investigated. Albumin secretion was analysed in parallel as a control viability and tissue specific secretory parameter. The results clearly show that the velocity of diazepam turnover increases between day 1 and 2 and stabilises at high levels. Typical diazepam metabolites including temazepam, N-desmethyl-diazepam and oxazepam were generated. Cell specific functions, including albumin secretion, were comparable to an in vivo liver. We conclude that the flat membrane bioreactor used as bioartificial liver has the potential to detoxify diazepam and ammonia at significant amounts. Maintenance of monoxygenase activities in vitro is one of the strongholds of the bioreactor concept presented in this study.

Albumins↗
PubMed2002

MELISSA: a loop of interconnected bioreactors to develop life support in space.

The development of a loop of interconnected continuous bioreactors, aimed to provide life support in space, is reported. The complete loop concept consists of four bioreactors and one higher plant compartment. For its realization the continuous and controlled operation of the bioreactors is characterized, up to the pilot scale level, first for each individual reactor, second for the interconnected reactor operation. The results obtained with the two more advanced bioreactors in the Micro Ecological Life Support System Alternative (MELISSA) loop are described more specifically. These reactors consist of a packed-bed reactor working with an immobilized co-culture of Nitrosomonas and Nitrobacter cells, and an external loop gas-lift photobioreactor for the culture of the cyanobacteria Spirulina platensis. Their individual operation for long duration runs has been achieved and characterized, and their interconnected operation at pilot scale is reported.

Bioreactors↗
PubMed1999

Computing operating diagrams of bioreactors.

The operating diagram of a bioreactor is an illustrative way to present the effect that the operating conditions have on its long-term behavior. It can be constructed if a mathematical model of the bioreactor is available. The procedure for constructing the operating diagram consists in analyzing the dynamic behavior of the system of the differential equations of the model. Some methods are described that can be used in computing operating diagrams of bioreactors. They are based on numerical bifurcation techniques for systems of differential equations. Both cases of bioreactors with constant and periodically varying operating conditions are considered.

Bioreactors↗
PubMedDate not supplied

Increase in beta-galactosidase activity in a non-isothermal bioreactor utilizing immobilized cells of Kluyveromyces fragilis: fundamentals and applications.

The beta-galactosidase activity of Kluyveromyces fragilis cells immobilized in a kappa carrageenan gel was studied in a bioreactor functioning under isothermal and non-isothermal conditions. We observed an increase in enzyme activity which was found to be proportional to the intensity of the temperature gradient applied across the biocatalytic membrane, as well as to the average temperature of the bioreactor. The efficiency of such a non-isothermal bioreactor was calculated with respect to the yield of a bioreactor working under comparable isothermal conditions and was evaluated in terms of reduction of processing times in industrial applications. The possibility that enzyme activity in living cells is affected by non-isothermal conditions naturally existing owing to metabolic heat production is also discussed.

Bioreactors↗
PubMed2001

Biodegradation of phenol in a continuous process: comparative study of stirred tank and fluidized-bed bioreactors.

The paper presents the main results obtained from the study of the biodegradation process of phenol by a pure culture of Pseudomonas putida ATCC 17484. The experimental work was carried out in two different systems: a stirred tank where cells grew as a suspended culture and a fluidized bed where cells were immobilized within calcium alginate gel beads. The influence of the hydraulic residence time (HRT) and organic loading rate on the removal efficiency of phenol was determined for both bioreactors. Also, the stability of the fluidized-bed bioreactor (FBB) in terms of its ability to withstand sudden phenol overdoses is also reported. Experimental values indicated that both bioreactors showed high phenol degradation efficiencies, higher than 90%, even for a phenol loading rate in the influent as high as 4 g phenol/l day. The FBB showed better performance than the suspended-culture bioreactor due to its better control and because it could operate with lower HRT.

Alginates↗
PubMed2002

Production of carboxylic acids from hydrolyzed corn meal by immobilized cell fermentation in a fibrous-bed bioreactor.

Corn meal hydrolyzed with amylases was used as the carbon source for producing acetic, propionic, and butyric acids via anaerobic fermentations. In this study, corn meal, containing 75% (w/w) starch, 20% (w/w) fibers, and 1.5% (w/w) protein, was first hydrolyzed using amylases at 60 degrees C. The hydrolysis yielded approximately 100% recovery of starch converted to glucose and 17.9% recovery of protein. The resulting corn meal hydrolyzate was then used, after sterilization, for fermentation studies. A co-culture of Lactococcus lactis and Clostridium formicoaceticum was used to produce acetic acid from glucose. Propionibacterium acidipropionici was used for propionic acid fermentation, and Clostridium tyrobutylicum was used for butyric acid production. These cells were immobilized on a spirally wound fibrous matrix packed in a fibrous-bed bioreactor (FBB) developed for multi-phase biological reactions or fermentation. The bioreactor was connected to a stirred-tank fermentor that provided pH and temperature controls via medium circulation. The fermentation system was operated at the recycle batch mode. Temperature and pH were controlled at 37 degrees C and 7.6, respectively, for acetic acid fermentation, 32 degrees C and 6.0, respectively, for propionic acid fermentation, and 37 degrees C and 6.0, respectively, for butyric acid production. The fermentation demonstrated a yield of approximately 100% and a volumetric productivity of approximately 1 g/(1 h) for acetic acid production. The propionic acid fermentation achieved an approximately 60% yield and a productivity of 2.12 g/(1 h), whereas the butyric acid fermentation obtained an approximately 50% yield and a productivity of 6.78 g/(1 h). These results were comparable to, or better than those fermentations using chemically defined media containing glucose as the substrate, suggesting that these carboxylic acids can be efficiently produced from direct fermentation of corn meal hydrolyzate. The corn fiber present as suspended solids in the corn meal hydrolyzate did not cause operating problem to the immobilized cell bioreactor as is usually encountered by conventional immobilized cell bioreactor systems. It is concluded that the FBB technology is suitable for producing value-added biochemicals directly from agricultural residues or commodities such as corn meal.

Acetic Acid↗
PubMedDate not supplied

Design of a molecular chaperone-assisted protein folding bioreactor.

Escherichia coli molecular chaperone GroEL and co-chaperone GroES are well known to assist the folding/refolding of a diverse range of substrate proteins. Despite this, there have been relatively few reports of the GroEL/GroES molecular chaperone system being used as a biotechnology tool for protein folding/refolding. In this paper, a solution-phase protein folding bioreactor is described that involves the complete GroEL/GroES system. The main features of this bioreactor are the use of a stirred-cell concentrator fitted with a 100 kDa molecular weight cutoff membrane and an attached buffer reservoir. This bioreactor system was used successfully for assisted-batch refolding of guanidinium chloride (Gu-HCl) unfolded mitochondrial malate dehydrogenase (mMDH). We believe that protein folding bioreactor systems of this type could have wide potential utility for the folding/refolding of unfolded protein substrates.

Animals↗
PubMedDate not supplied

New miniaturized hollow-fiber bioreactor for in vivo like cell culture, cell expansion, and production of cell-derived products.

We have developed a miniaturized hollow-fiber bioreactor system for mammalian cell culture with a volume of 1 mL. Cell and medium compartments of the bioreactor are separated by a semipermeable membrane, and oxygenation of the cell compartment is accomplished using an oxygenation membrane. As a result of the geometry of the transparent housing, cells can be observed by microscopy during culture. The leukemic cell lines CCRF-CEM, HL-60, and REH were cultivated up to densities of 3.5 x 10(7)/mL without medium change or manipulation of the cells. As shown using CCRF-CEM cells, growth in the bioreactor was strongly influenced and could be controlled by the medium flow rate. As a consequence, consumption of glucose and generation of lactate varied with flow rate. Depending on the molecular size cutoff of the membranes used, added growth factors such as GM-CSF, as well as factors secreted from the cells, are retained in the cell compartment for up to 1 week. This new miniaturized hollow-fiber bioreactor offers advantages in tissue engineering by continuous nutrient supply for cells in high density, retention of added or autocrine produced factors, and undisturbed long-term culture in a closed system.

Animals↗
PubMedDate not supplied

A novel parallel shaken bioreactor system for continuous operation.

A novel continuous bioreactor system was developed as a shaken culture vessel for the investigation of the growth kinetics and product formation of microorganisms in milliscale. The novel bioreactor system mainly consists of a specially designed 250-mL shake flask with two inlets, one for gas supply and one for medium supply, and one combined outlet on the side of flask for exhaust gas and culture liquid. As a result of the circulating motion of the fermentation broth in the shake flask, the maximum liquid height reaches the edge of the outlet and the fermentation broth is accelerated into the outlet by centrifugal force. Additionally, the excess fermentation broth leaving the culture vessel is continuously driven by the exhaust gas. Because of the small scale and the simple handling it is possible to operate many of these shaken bioreactor vessels simultaneously. By using parallel vessels operated at different dilution rates on the same shaker, the data for a complete biomass over dilution rate (X-D) diagram of a biological culture can be evaluated in an efficient manner, thus saving money, materials, and time. Continuous fermentations of the yeast Saccharomyces cerevisiae H1022 (ATCC 32167) in the shaken bioreactor system and in a conventional stirred tank fermentor showed very similar results.

Bioreactors↗
PubMedDate not supplied

Production of recombinant adeno-associated viral vectors using a baculovirus/insect cell suspension culture system: from shake flasks to a 20-L bioreactor.

Production of recombinant adeno-associated viral vectors using a baculovirus/insect cell system at various scales is presented. Shake flask studies were conducted to assess conditions to be used in bioreactors. Two insect cell lines, Trichoplusia ni (H5) and Spodoptera frugiperda (Sf9), were compared for their ability to produce rAAV-2 after infection with recombinant baculoviruses coding for the essential components of the vector. The effect of varying the ratio between individual baculoviruses and the effect of the overall multiplicity of infection (MOI), as well as the cell density at infection, were also examined. Infectious rAAV-2 particles were proportionally produced when increasing the individual MOI of BacRep virus up to 1.6. When equal amounts of each virus were used, a leveling effect occurred beyond an overall MOI of 5 and a maximum titer was obtained. Increasing the cell density at infection resulted in higher yields when infecting the cells in fresh medium; however, for the production of bioactive particles, an optimal peak cell density of approximately 1 x 10(6) cells/mL was observed without medium exchange. Infection in 3- and 20-L bioreactors was done at an overall MOI of 5 with a ratio of the three baculoviruses equal to 1:1:1. Under these conditions and infecting the cells in fresh medium, a total of approximately 2.2 x 10(12) infectious viral particles (bioactive particles) or 2.6 x 10(15) viral particles were produced in a 3-L bioreactor. Without replacing the medium at infection, similar titers were produced in 20 L. Our data demonstrates the feasibility of rAAV-2 production by BEVS at various scales in bioreactors and indicates that further optimization is required for production at high cell densities.

Animals↗
PubMedDate not supplied

Efficient production of L-(+)-lactic acid using mycelial cotton-like flocs of Rhizopus oryzae in an air-lift bioreactor.

L-(+)-Lactic acid production was enhanced in a culture of Rhizopus oryzae by induction of a mycelial flocs morphology. By conventional culture the morphology of R. oryzae is that of a pellet-like cake; however, when mineral support and poly(ethylene oxide) are added to the culture, the morphology of R. oryzae takes on a cotton-like appearance. The formation of these cotton-like mycelial flocs was induced by the addition of 5 ppm poly(ethylene oxide) into a 12-14 h culture containing 3 g/L of the mineral support before the formation of the conventional pellet morphology. The cotton-like flocs were also formed in cultures grown in an air-lift bioreactor. This morphology allowed effective mass transfer inside the flocs and effective fluidity of culture broth in an air-lift bioreactor. L-(+)-Lactic acid concentration produced by mycelial flocs in an air-lift bioreactor, with the support and poly(ethylene oxide), was 104.6 g/L with a yield of 0.87 using 120 g/L of glucose as the substrate; for this culture without both, the concentration was 43.2 g/L. These results demonstrate that cotton-like mycelial flocs are the optimal morphology for use in the air-lift bioreactor culture of R. oryzae.

Bioreactors↗
PubMedDate not supplied

Simultaneous biodegradation of benzene, toluene, and p-xylene in a two-phase partitioning bioreactor: concept demonstration and practical application.

In this work, a mixture of benzene, toluene, and p-xylene was simultaneously biodegraded by Pseudomonas sp. ATCC 55595 in a two-phase partitioning bioreactor. This bioreactor consisted of a 1-L cell-containing aqueous medium phase and a 500-mL immiscible organic phase. The organic solvent systematically selected for use in the bioreactor was Adol 85 NF, an industrial-grade, biocompatible solvent. In the first of three experiments, the organic phase was loaded with 2.0 g of benzene, 10.15 g of toluene, and 2.1 g of p-xylene, which partitioned into the aqueous phase at concentrations of 25, 50, and 8 mg/L, respectively. The system ultimately biodegraded all of the substrates within 144 h. During the rapid growth phase of this fermentation, the cells were oxygen-limited. This fermentation was therefore repeated using an enriched air supply to remove the oxygen limitation. The use of enriched air ultimately reduced the length of the fermentation to 108 h, thereby improving the overall volumetric consumption rates. Finally, 500 mL of Adol were used to recover 2.0 g of benzene, 10.15 g of toluene, and 2.1 g of p-xylene from silica sand that was contaminated as part of a simulated soil "spill". The solvent washing procedure was able to recover greater than 99% of each compound from the contaminated soil. The Adol was then transferred to the two-phase bioreactor to permit biological treatment of the BTX contaminants. This process was repeated when the initial BTX load had been consumed almost to exhaustion, and the solvent was able to recover the contaminants at greater than 99% efficiency once again. The system was ultimately able to degrade 4.0 g of benzene, 20.2 g of toluene, and 4.2 g of p-xylene within 144 h. These results represent an unprecedented level of BTX degradation and illustrate a potential practical application for this novel biotechnology.

Benzene↗
PubMed2002

A model to predict long-term performance of vapor-phase bioreactors: a cellular automaton approach.

A novel numerical model was constructed to predict performance of vapor-phase bioreactors (VPBs) operated over extended periods. This model incorporates two unique features to simulate changes in pollutant removal efficiency and biomass accumulation: (1) total biomass is divided into two microbial components, active and inactive biomass, and (2) biomass growth and biofilm thickness changes are simulated by means of a cellular automaton (CA) approach. The CA approach, a differential-discrete algorithm, numerically allows the excess quantity of biomass in each numerical element to move toward the biofilm surface as biomass accumulates. One set of experimental bioreactor data was used to estimate unknown model parameters. A 90-day simulation using the estimated parameters agreed with pollutant removal and biomass accumulation profiles determined experimentally. Four additional model simulations using the same estimated model parameters were generally consistent with experimental data collected from a series of toluene-degrading VPBs operated over a range of conditions. Model predictions imply that the decline in bioreactor performance observed over extended operation was caused by a decline in the active biomass fraction and a decrease in the biofilm specific surface area. This CA model provides insight into biomass accumulation during complex bioreactor operation and improves our capability to predict long-term VPB performance.

Biofilms↗