Cultivation Mode

The bioreactor operation mode is normally defined at the outset of process configuration. Insect cells have been cultured in almost all known cultivation modes batch [10], repeated-batch [70], perfusion [71-74], fed-batch [75, 76], semi-continuous [77,78] and continuous [79]. In spite of this multitude of different strategies, the batch or, eventually, fed-batch mode is normally preferred due to the lytic infection cycle of the baculovirus. 

Equations 8 and 9, previously shown for the substrate and product mass balances in continuous cultures, can also be applied to this cultivation mode. However, due to cell retention, the equation that expresses the cell mass balance is altered, when compared with the mass balance of cells in a continuous culture (Equation 11) ... 

The following cultivation modes have been described for production of MAbs in in vitro large-scale systems batch, fed-batch, chemostat and perfusion (Reuveny Lazar, 1989). Batch and fed-batch processes are the most common methods. More demanding are chemostat and perfusion modes, which allow a continuous production of MAbs. All methods are applicable in homogeneous and, with the exception of chemostat, non-homogeneous systems. 

Table 8.1 SCO production from various microorganisms, carbon sources, and cultivation modes... 

Microorganism Cultivation mode Carbon source Total dry weight (g/L) MO content (%, w/w) Productivity (g/L/h) References... 

Carvalho, A.P. and Malcata, FJC (2005) Optimization of w-3 fatty acid production by microalgae crossover effects of CO2 and light intensity under batch and continuous cultivation modes. Mar. Biotechnol., 7, 381-388. 

A simple method for the conversion of 1.6 m 3-cyanopyridine to nicotinic acid in fed-batch mode of addition of substrate into the reaction catalysed by resting cells of G. terrae NDB 1165 has been described. A procedure for cultivation of G. terrae NDB 1165 and recovery of nicotinic acid from the reaction mixture is described. Using these procedures, 196 g of nicotinic acid (90 % recovery) can be practically produced in a reaction volume of 1 L. 

Santos, J.C., Silva, S.S., Mussatto, S.I., Carvalho, W. and Cunha, M.A.A., Immobilized cells cultivated in semi-continuous mode in a fluidized bed reactor for xylitol production from sugarcane bagasse, World. Microbiol. Biotech., 21 (2005) 531-535. 

Commercial scale cultivation of mammalian cells is accompHshed using different technologies roller bottles, microcarriers, suspension (batch, fed-batch or perfusion mode) and hollow fiber bioreactors (Table 2). However, especially for products needed in large amounts, suspension cultivation seems to be the most effective system [4, 5]. Suspension-based systems are characterized by a homogeneous concentration of cells, nutrients, metabolites and product, thereby facilitating scale-up [6] and enabling an accurate monitoring and control of the culture [7]. 

Mammalian cells were cultivated in high cell density perfusion operation mode for the production of therapeutically important proteins. Material and energy balances were determined and cell regulation was investigated. Methods were developed for the recovery and purification of the products with chromatography and expanded bed chromatography. 

Only a very few experiments have been published concerning the behaviour of osteoclast cells on fluoridated biomaterial surfaces, although this point seems crucial concerning the mode of action of osteoclast cells. Most studies report on the effect of fluoride ions in the solution, which may also change the surface on which these cells are cultivated. Ramaswamy et al. [191] have shown that osteoclasts attach to FA ceramic surfaces but that the resorption pits were barely observed. It is accepted that due to the very slow solubility of fluorapatite... 

It means too, however preoccupied you may be with minding the shop , cultivating the attitude of mind of a creative leader. You need to be able to move freely between the reactive and proactive modes of managing. 

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