Nutrients continuous supply

Continuous culture A method of eultivation in whieh nutrients are supplied and produets are removed eontinuously at volumetrieally equal rates maintaining the eells in a eondition of stable multiplieation and growth. 

In this case, there is a continuous supply of nutrients and a continuous withdrawal of the culture broth including the submerged free cells. The governing equations for continuous cultures are the same as the ones for fed-batch cultures (Equations 7.20-7.22). The only difference is that feed flowrate is normally equal to the effluent flowrate (Fm=Fout=F) and hence the volume. V, stays constant throughout the culture. 

Continuous culture systems have been widely used to culture microorganisms for industrial and research purposes (Kubitschek 1970 Tempest 1970 Veldkamp 1976 Rhee 1980). In recent years, these culture techniques have found their way into the bioassay methods of ecotoxicology and allelopathy (Rhee 1980). The early development of a continuous culture system can be traced back to the work of Novik and Szilard (1950 a,b) who developed the first chemostat. In a continuous culture system, nutrients are supplied to the cell culture at a constant rate and to maintain a constant volume, an equal volume of cell culture is removed. This allows the cell population to reach a steady state, where the growth rate and the total number of cells/ml of culture remains constant. Two kind of continuous culture systems can be distinguished turbidostat and chemostat. ... 

Bioremediation usually requires a procedure for stimulation of and maintaining the activity of microorganisms. For biodegradation to be successful, it is necessary to provide a continuous supply of a suitable electron acceptor (such as oxygen or nitrate), nutrients (nitrogen, phosphorus), and a carbon source for energy and cell material. The most commonly deficient components in the subsurface are eiectron acceptors and nutrients. 

The GI system is responsible at its most basic level for providing a continual supply of water, electrolytes, minerals, and nutrients. This is achieved by a myriad of specialized cells and coordinated interplay of motility, secretion, digestion, absorption, blood flow, and lymph flow. These components are under elaborate control of the central and enteric nervous systems, endocrine and paracrine regulation of hormones. The highly complex nature of GI function is clearly illustrated by the estimate that 80 to 100 million neurons exist within the enteric nervous system, a number comparable to that found within the spinal column, hence described as a "second brain."171... 

Composting, however, is more than a way of recycling plant wastes. Compost builds soil stracture, increases the ability of soil to retain water, reduces erosion, improves aeration and supplies nutrients. Nutrients from compost are supplied slowly early in the season when plants are small, then more rapidly as soils warm and plants grow faster. Certain nutrients continue to be supplied for several years as compost breaks down thus, compost eiuiches soils in proportion to the amount used. 

The most sophisticated technique for stem cell expansion is the Aastrom-Rephcell system (Aastrom Biosciences Inc., Ann Arbor, Ml, USA), which is an automated clinical system for the onsite expansion of stem cells in cancer therapy. It consists of a grooved perfusion chamber for the retention of the hematopoietic cells, with the medium flow perpendicular to the channel grooves resulting in a continuous supply of fresh nutrients while metabolites are simultaneously removed [47,71,72]. This technique has already been used in a number of clinical studies [73,74]. No incompatibihty of the expanded cells was found,but the expansion of the early progenitor cells was rather low [75]. 

Suspension cultures present some advantages in comparison with adherent cell cultures. Large cell quantities can be attained without increasing the superficial area of the substratum. Also, a steady state can be reached if nutrients are continuously supplied and cell concentration is kept constant. This can rarely be achieved with a monolayer culture. Cells in different modes (adherent or suspension) behave differently with regard to proliferation, enzymatic activity, glycolysis, respiration, specialized product synthesis, and many other properties. 

Continuous culture A method of cultivation in which nutrients are supplied and products are removed continuously at volumetrically equal rates maintaining the cells in a condition of stable multiplication and growth. 

The relative order of efficiency of accumulation of the thpee radionuclides into edible tissues was Zn>Fe>Se. Most of the Zn transported to the above ground plant parts was accumulated by the seeds, however, much of the dose of each of the radionuclides remained in the roots and nutrient solution. The calculated percent of the applied dose taken up by soybean leaves is underestimated since some of the leaves abscised as the plants senesced and they were discarded. Zinc and iron have been classified as partially mobile in the phloem (8). Translocation of iron within plants is poor since new growth of plants require a continuous supply of iron via the xylem or from external applications ( ). Zinc deficiencies of plants can be corrected by applying ZnSO. in a dilute spray. However, iron deficiences of plants are usually difficult to correct which implies a lesser mobility within the plant. 

Perfusion systems have also been used for successful scale-up of MoAb production. During the culture period, cell growth occurs exponentially until the cell density reaches a maximum. At that point, the medium needs a continuous supplementation of fresh nutrients and elimination of waste. In perfusion systems, fresh nutrients are supplied and wastes are removed continuously so that the medium meets the physiological needs of the cells. At steady state, the cell concentration is determined by space and other limitations. High cell densities have been achieved by immobilizing the cells in porous ceramic matrices or hollow fiber devices. Intermediate cell densities have been achieved by perfusion reactors with a spin filter, or in a fluidized bed reactor in which the cells are embedded in sponge-like... 

Perfusion MBRs have been introduced for the production of monoclonal antibodies. The mammalian cells that synthesize them are grown in the extracapillary space between the fibers in the module. Nutrients are supplied through the fibers, which also extract the metabolites continuously. The high cell concentrations between the fibers initiate high antibody harvests. These MBRs are also being investigated as an alternative concept for bioartificial organs such as liver and pancreas. 

The sea floor is an important site for nutrient regeneration and acts as a source of continual supply of remineralized organic constituents to... 

Dissimilatory ferric iron reducing-microbes require a continued supply of ferric iron and other nutrients to degrade a significant volume of petroleum. Thus, the original emplacement of extensive ferric iron in a form accessible to microbes during early diagenesis of the Kuparuk... 

The use of N-N as a tracer has thrown some new light on the problem but it is still far from solved. Such experiments-Jiave shown that excised nodules will fix very small amounts of nitrogen, but such fixation continues for only a few hours even though the nodules are suspended in a complete nutrient medium. It seems that a normally-functioning plant that continually supplies the nodular tissue with substances required in the fixation process is essential. At least, no one has been able to find a replacement for these plant juices. The attached nodule also continually removes the end product of fixation but such removal is of secondary importance. 

Fed-batch cultivation is a fermentation strategy whereby one or more nutrients are supplied to the cell culture until the end of the process. The concentration of nutrients that are fed into the bioreactor can be controlled by regulating the feed rate. In fed-batch cultivation the cells are fed continuously as per the required feeding method regime... 

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