Showing papers on "Bioreactor published in 2005"

Application of bioreactor systems for large scale production of horticultural and medicinal plants

Abstract: Automation of micropropagation via organogenesis or somatic embryogenesis in a bioreactor has been advanced as a possible way of reducing costs. Micropropagation by conventional techniques is typically a labour-intensive means of clonal propagation. The paper describes lower cost and less labour-intensive clonal propagation through the use of modified air-lift, bubble column, bioreactors (a balloon-type bubble bioreactor), together with temporary immersion systems for the propagation of shoots, bud-clusters and somatic embryos. Propagation of Anoectochilus, apple, Chrysanthemum, garlic, ginseng, grape, Lilium, Phalaenopsis and potato is described. In this chapter, features of bioreactors and bioreactor process design specifically for automated mass propagation of several plant crops are described, and recent research aimed at maximizing automation of the bioreactor production process is highlighted.

Treatment of dairy effluents in an aerobic granular sludge sequencing batch reactor

Abstract: Aerobic granular sludge can successfully be cultivated in a sequencing batch reactor (SBR) treating dairy wastewater. Attention has to be paid to the fact that suspended solids are always present in the effluent of aerobic granular sludge reactors, making a post-treatment step necessary. Sufficient post-treatment can be achieved through a sedimentation process with a hydraulic retention time of 15–30 min. After complete granulation and the separation of biomass from the effluent, removal efficiencies of 90% CODtotal, 80% Ntotal and 67% Ptotal can be achieved at a volumetric exchange ratio of 50% and a cycle duration of 8 h. Effluent values stabilize at around 125 mg l−1 CODdissolved. The maximum applicable loading rate is nevertheless limited, as the stability of aerobic granules very much depends on the presence of distinct feast and famine conditions and the degradation of real wastewaters shows slower kinetics compared with synthetic wastewaters. As loading rate and volumetric exchange ratio are coupled in an SBR system, the potential of granular sludge for improving process efficiency is also limited.

Bioreactor Performance in Anaerobic Digestion of Fruit and Vegetable Wastes

Abstract: This work reviews the potential of anaerobic digestion for material recovery and energy production from fruit and vegetable wastes (FVW). These wastes contain 8–18% total solids (TS), with a total volatile solids (VS) content of 86–92%. The organic fraction includes about 75% easy biodegradable matter (sugars and hemicellulose), 9% cellulose and 5% lignin. Anaerobic digestion of FVW was studied under different operating conditions using different types of bioreactors. It permits the conversion of 70–95% of organic matter to methane, with a volumetric organic loading rate (OLR) o f 1–6.8 g versatile solids (VS)/l day. A major limitation of anaerobic digestion of FVW is a rapid acidification of these wastes decreasing the pH in the reactor, and a larger volatile fatty acids production (VFA), which stress and inhibit the activity of methanogenic bacteria. Continuous two-phase systems appear as more highly efficient technologies for anaerobic digestion of FVW. Their greatest advantage lies in the buffering of the organic loading rate taking place in the first stage, allowing a more constant feeding rate of the methanogenic second stage. Using a two-stage system involving a thermophilic liquefaction reactor and a mesophilic anaerobic filter, over 95% volatile solids were converted to methane at a volumetric loading rate of 5.65 g VS/l d. The average methane production yield was about 420 l/kg added VS.

Development, parallelization, and automation of a gas-inducing milliliter-scale bioreactor for high-throughput bioprocess design (HTBD).

Abstract: A novel milliliter-scale bioreactor equipped with a gas-inducing impeller was developed with oxygen transfer coefficients as high as in laboratory and industrial stirred-tank bioreactors. The bioreactor reaches oxygen transfer coefficients of >0.4 s−1. Oxygen transfer coefficients of >0.2 s−1 can be maintained over a range of 8- to 12-mL reaction volume. A reaction block with integrated heat exchangers was developed for 48-mL-scale bioreactors. The block can be closed with a single gas cover spreading sterile process gas from a central inlet into the headspace of all bioreactors. The gas cover simultaneously acts as a sterile barrier, making the reaction block a stand-alone device that represents an alternative to 48 parallel-operated shake flasks on a much smaller footprint. Process control software was developed to control a liquid-handling system for automated sampling, titration of pH, substrate feeding, and a microtiter plate reader for automated atline pH and atline optical density analytics. The liquid-handling parameters for titration agent, feeding solution, and cell samples were optimized to increase data quality. A simple proportional pH-control algorithm and intermittent titration of pH enabled Escherichia coli growth to a dry cell weight of 20.5 g L−1 in fed-batch cultivation with air aeration. Growth of E. coli at the milliliter scale (10 mL) was shown to be equivalent to laboratory scale (3 L) with regard to growth rate, μ, and biomass yield, YXS. © 2005 Wiley Periodicals, Inc.

Stirred-tank reactor system

Abstract: The present invention relates to a stirred-tank reactor system and methods of preparing such systems. The present invention further encompasses the use of the stirred-tank reactor system as a disposable bioreactor (104) and in kits with disposable elements.

Competition and coexistence of aerobic ammonium- and nitrite-oxidizing bacteria at low oxygen concentrations

Abstract: In natural and man-made ecosystems nitrifying bacteria experience frequent exposure to oxygen-limited conditions and thus have to compete for oxygen. In several reactor systems (retentostat, chemostat and sequencing batch reactors) it was possible to establish co-cultures of aerobic ammonium- and nitrite-oxidizing bacteria at very low oxygen concentrations (2–8 μM) provided that ammonium was the limiting N compound. When ammonia was in excess of oxygen, the nitrite-oxidizing bacteria were washed out of the reactors, and ammonium was converted to mainly nitrite, nitric oxide and nitrous oxide by Nitrosomonas-related bacteria. The situation could be rapidly reversed by adjusting the oxygen to ammonium ratio in the reactor. In batch and continuous tests, no inhibitory effect of ammonium, nitric oxide or nitrous oxide on nitrite-oxidizing bacteria could be detected in our studies. The recently developed oxygen microsensors may be helpful to determine the kinetic parameters of the nitrifying bacteria, which are needed to make predictive kinetic models of their competition.

Fate and biodegradability of sulfonated aromatic amines

Abstract: Ten sulfonated aromatic amines were tested for their aerobic and anaerobic biodegradability and toxicity potential in a variety of environmental inocula. Of all the compounds tested, only two aminobenzenesulfonic acid (ABS) isomers, 2- and 4-ABS, were degraded. The observed degradation occurred only under aerobic conditions with inocula sources that were historically polluted with sulfonated aromatic amines. Bioreactor experiments, with non-sterile synthetic wastewater, confirmed the results from the aerobic batch degradation experiments. Both ABS isomers were degraded in long-term continuous experiment by a bioaugmented enrichment culture. The maximum degradation rate in the aerobic bioreactor was 1.6-1.8 g 1(-1) d(-1) for 2-ABS and a somewhat lower value for 4-ABS at hydraulic retention times (HRT) of 2.8-3.3 h. Evidence for extensive mineralization of 2- and 4-ABS was based on oxygen uptake and carbon dioxide production during the batch experiments and the high levels of chemical oxygen demand (COD) removal in the bioreactor. Furthermore, mineralization of the sulfonate group was demonstrated by high recovery of sulfate. The sulfonated aromatic amines did not show any toxic effects on the aerobic and anaerobic bacterial populations tested. The poor biodegradability of sulfonated aromatic amines indicated under the laboratory conditions of this study suggests that these compounds may not be adequately removed during biological wastewater treatment.

Simple bioreactors for mass propagation of plants

Abstract: Bioreactors provide a rapid and efficient plant propagation system for many agricultural and forestry species, utilizing liquid media to avoid intensive manual handling. Large-scale liquid cultures have been used for micropropagation through organogenesis or somatic embryogenesis pathways. Various types of bioreactors with gas-sparged mixing are suitable for the production of clusters of buds, meristems or protocorms. A simple glass bubble-column bioreactor for the proliferation of ornamental and vegetable crop species resulted in biomass increase of 3 to 6-fold in 3–4 weeks. An internal loop bioreactor was used for asparagus, celery and cucumber embryogenic cultures. However, as the biomass increased, the mixing and circulation were not optimal and growth was reduced. A disposable pre-sterilized plastic bioreactor (2–5-l volume) was used for the proliferation of meristematic clusters of several ornamental, vegetable and woody plant species. The plastic bioreactor induced minimal shearing and foaming, resulting in an increase in biomass as compared to the glass bubble-column bioreactor. A major issue related to the use of liquid media in bioreactors is hyperhydricity, that is, morphogenic malformation. Liquid cultures impose stress signals that are expressed in developmental aberrations. Submerged tissues exhibit oxidative stress, with elevated concentrations of reactive oxygen species associated with a change in antioxidant enzyme activity. These changes affect the anatomy and physiology of the plants and their survival. Malformation was controlled by adding growth retardants to decrease rapid proliferation. Growth retardants ancymidol or paclobutrazol reduced water uptake during cell proliferation, decreased vacuolation and intercellular spaces, shortened the stems and inhibited leaf expansion, inducing the formation of clusters. Using a two-stage bioreactor process, the medium was changed in the second stage to a medium lacking growth retardants to induce development of the meristematic clusters into buds or somatic embryos. Cluster biomass increased 10–15-fold during a period of 25–30 days depending on the species. Potato bud clusters cultured in 1.5 1 of medium in a 2-l capacity bioreactor, increased during 10–30 days. Poplar in vitro roots regenerated buds in the presence of thidiazuron (TDZ); the biomass increased 12-fold in 30 days. Bioreactor-regenerated clusters were separated with a manual cutter, producing small propagule units that formed shoots and initiated roots. Clusters of buds or meristematic nodules with reduced shoots, as well as arrested leaf growth, had less distortion and were optimal for automated cutting and dispensing. In tuber-, bulb- and corm-producing plants, growth retardants and elevated sucrose concentrations in the media were found to enhance storage organ formation, providing a better propagule for transplanting or storage. Bioreactor-cultures have several advantages compared with agar-based cultures, with a better control of the contact of the plant tissue with the culture medium, and optimal nutrient and growth regulator supply, as well as aeration and medium circulation, the filtration of the medium and the scaling-up of the cultures. Micropropagation in bioreactors for optimal plant production will depend on a better understanding of plant responses to signals from the microenvironment and on specific culture manipulation to control the morphogenesis of plants in liquid cultures.

Combined carbon and nitrogen removal from acetonitrile using algal-bacterial bioreactors.

Abstract: When compared with Chlorella vulgaris, Scenedesmus obliquus and Selenastrum capricornutum, C. sorokiniana presented the highest tolerance to acetonitrile and the highest O2 production capacity. It also supported the fastest acetonitrile biodegradation when mixed with a suitable acetonitrile-degrading bacterial consortium. Consequently, this microalga was tested in symbiosis with the bacterial culture for the continuous biodegradation of acetonitrile at 2 g l−1 in a stirred tank photobioreactor and in a column photobioreactor under continuous illumination (250 μE m−2 s−1). Acetonitrile removal rates of up to 2.3 g l−1 day−1 and 1.9 g l−1 day−1 were achieved in the column photobioreactor and the stirred-tank photobioreactor, respectively, when operated at the shortest retention times tested (0.4 days, 0.6 days, respectively). In addition, when the stirred-tank photobioreactor was operated with a retention time of 3.5 days, the microbial culture was capable of assimilating up to 71% and nitrifying up to 12% of the NH4+ theoretically released through the biodegradation of acetonitrile, thus reducing the need for subsequent nitrogen removal. This study suggests that complete removal of N-organics can be combined with a significant removal of nitrogen by using algal–bacterial systems and that further residual biomass digestion could pay-back part of the operation costs of the treatment plant.

Microbioreactor for continuous cell culture

Abstract: The present invention microscale bioreactors (microfermentors) and microscale bioreactor arrays for use in culturing cells. The microfermentors include a vessel for culturing cells and means for providing oxygen to the interior of the vessel at a concentration sufficient to support cell growth, e.g., growth of bacterial cells. Depending on the embodiment, the microfermentor vessel may have various interior volumes of less than approximately 1 ml. The microfermentors may include an aeration membrane and optionally a variety of sensing devices. Methods of using the microfermentors, e.g., to select optimum cell strains or bioprocess parameters are provided. The microbioreactors having a variety of different designs, some of which incorporate active fluid mixing and/or have the capability to operate in batch, fed-batch, or continuous mode. In certain embodiments the microreactors operate as microchemostats. Methods for culturing cells under chemostat conditions in a microbioreactor are also provided.

Production of Biomass and Ginsenosides from Adventitious Roots of Panax ginseng in Bioreactor Cultures

Abstract: Organic nutrients play a central role during Panax ginseng adventitious root culture in bioreactor systems. To understand how the nutrient elements were uptaken during the adventitious root growth as well as the production of biomass and natural ginsenosides, a biotechnological approach to identifying the nutritional physiology of ginseng in a commercial-scale bioreactor was necessary. Normal MS medium nutrient in the bioreactor culture of adventitious roots resulted in slow growth, low biomass, and Rg and Rb ginsenoside contents. When the ginsenoside production increased to higher levels, a group of regulatory nutritional elements that have the potential to interact with biomass was identified. The effects of the salt strength of the medium, of macroelements, metal elements, the ammonia/nitrate ratio, sucrose concentration, and osmotic agents on the growth, the formation of biomass and the production of ginsenosides from adventitious roots were investigated. Appropriate conditions allowed for a maximum ginsenoide production of up to 12.42 [mg/g DW] to be obtained after 5 weeks of culture. The results demonstrated that the key organic nutrients can be regulated to improve the biomass and growth, and increase the ginsenoside yield in bioreactor cultures of P. ginseng adventitious roots.

Prediction of gas-liquid mass transfer coefficient in sparged stirred tank bioreactors.

Abstract: Oxygen mass transfer in sparged stirred tank bioreactors has been studied. The rate of oxygen mass transfer into a culture in a bioreactor is affected by operational conditions and geometrical parameters as well as the physicochemical properties of the medium (nutrients, substances excreted by the micro-organism, and surface active agents that are often added to the medium) and the presence of the micro-organism. Thus, oxygen mass transfer coefficient values in fermentation broths often differ substantially from values estimated for simple aqueous solutions. The influence of liquid phase physicochemical properties on kLa must be divided into the influence on k(L) and a, because they are affected in different ways. The presence of micro-organisms (cells, bacteria, or yeasts) can affect the mass transfer rate, and thus kLa values, due to the consumption of oxygen for both cell growth and metabolite production. In this work, theoretical equations for kLa prediction, developed for sparged and stirred tanks, taking into account the possible oxygen mass transfer enhancement due to the consumption by biochemical reactions, are proposed. The estimation of kLa is carried out taking into account a strong increase of viscosity broth, changes in surface tension and different oxygen uptake rates (OURs), and the biological enhancement factor, E, is also estimated. These different operational conditions and changes in several variables are performed using different systems and cultures (xanthan aqueous solutions, xanthan production cultures by Xanthomonas campestris, sophorolipids production by Candida bombicola, etc.). Experimental and theoretical results are presented and compared, with very good results.