Bioreactor growth

Processing food to ensure safety requires the reduction of viable endospores to a negligible level. Because it is impossible to ensure that all spores are completely eliminated, a standard reduction rate of 10" has been accepted. That means that one surviving endospore for each 10 cans processed is acceptable. Through a combination of temperature and time, thermal processes for food sterilization can be designed (Teixeira, 1992 Johnson, 1999). Similar considerations are important for the sterilization of medical devices and bioreactor growth media. 

The manipulation of cellular metabolic pathways in bioreactors is the aim of metabolic engineering. Cells are used that are capable of producing useful biochemicals. However, they often don t produce them in economical qnantities. Changing the genetic machinery of the cell or changing the composition of the bioreactor growth medium can enhance by several hundred percent the amounts of useful products. 

Water Groundwater can be treated in anaerobic bioreactors that encourage the growth of sulfate reducing bacteria, where the metals are reduced to insoluble sulfides, and concentrated in the sludge. For example, such a system is in use to decontaminate a zinc smelter site in the Netherlands (95). 

Loop reactors are particularly suitable as bioreactors to produce, for example, single-cell protein (96). In this process, single yeast or bacteria ceUs feeding on methanol multiply in aqueous culture broths to form high value biomass at 35—40°C, 20 kg/m ceU concentrations, and specific growth rates of... 

Fed-batch culture A cell cultivation technique in which one or more nutrients are supplied to the bioreactor in a given sequence during the growth or bioconversion process while the products remain in the vessel until the end of the run. 

You have now demonstrated the capability of exponentially increasing microbial populations to rapidly produce protein. However, although such outputs of protein are possible in theory, they cannot be achieved in practice, since exponential growth cannot be maintained for such periods because bioreactors are limited in size. 

The growth of cells on a large scale is called industrial fermentation. Industrial fermentation is normally performed in a bioreactor, which controls aeration, pH and temperature. Microorganisms utilise an organic source and produce primary metabolites such as ethanol,... 

Fig. 3.9. Growth simulation of C. ljungdahlii on synthesis gas in batch bioreactor, the experimental data are average...

Table E.10.1. Microbial growth in a batch fermentation bioreactor...

Non-stirred, aerated vessels are used in the process for traditional products such as wine, beer and cheese production. Most of the newly found bioprocesses require microbial growth in an aerated and agitated system. The percentage distribution of aerated and stirred vessels for bioreactor applications is shown in Table 6.1. The performances of various bioreactor systems are compared in Table 6.2. Since these processes are kinetically controlled, transport phenomena are of minor importance. 

Heat transfer is needed to operate the bioreactor at constant temperature, as the desired optimal microbial growth temperature. 

The Monod rate model is valid for a CSTR bioreactor with maximum specific growth rate of 0.5 li 1 and K, 2 g-1. What would be a suitable dilution rate at steady-state condition, where there is no cell death if initial substrate concentration is 50g-l-1 and yield of biomass on substrate is 100%. 

The inoculate was prepared in 250 ml flasks containing 100 ml of growth medium, which is inoculated with 10 ml of spore suspension. The mixture was shaken at 250 rpm and the temperature was controlled at 26 °C for 48 h. Then, 110 ml of resulting mycelia suspension is used to inoculate a 1000 ml broth in the airlift fermenter. The sterilised media are slowly pumped into the bioreactor at a flow rate of about lOOmlh-1 until 2 1 working volume is fully utilised. Aeration rates of 0.5, 1 and 2vvm (1,2 and 4 1 air/min) are used.6,7 Samples were taken at 24 hour intervals and evaluated for biomass, sugars and antibiotic concentrations. 

Foam in the bioreactor is troublesome it can reduce the oxygen transfer rate (OTR). Antifoam is use to prevent foam formation. However, excess antifoam may cause growth inhibition in the course of fermentation. The simplest device is known as a foam breaker, which is mounted on the stirrer shaft located on the surface of liquid. It is a flat blade. 

A special CSTR fermentation known as a chemostat bioreactor is used for microbial cell growth. The rate of biomass generation is given by ... 

If you aerate a bioreactor, power consumption is much less than a non-aerated bioreactor. Oxygen transfer rate, OTR 6 X 10 3 kgm-3 Oxygen uptake rate, OUR 0.65 mmol 02 kg 1 cell Specific growth rate, umax 0.5 h 1... 

Tlie biochemical reaction rate followed the Monod rate model with a Monod rate constant of ks = 6.2 X 10 6g-cm 3 and a specific growth rate of vmlx 6.67 X 10 7g-cm 3-s. Design the bioreactor with a suitable heat transfer area. 

Batch fermentation means the cultivation of microorganisms, where the sterile growth medium in desired volume is inoculated with the microorganisms into the bioreactor and no additional growth medium is added during the fermentation. The product will be harvested at the end of the process. Typically, PHA s production is performed using batch fermentation because of low cost for investment and no special control. In addition, sterilization of the feed stock is easier than other fermentation processes, and operation is flexible. 

Tramper J, Joustra D, Vlak, JM (1987) Bioreactor design for growth of shear-sensitive insect ceU. In Webb C, Mavitima R (eds) Plant animal ceU ciUtiu es process possibUities. Ellis Horwood, England... 

The influence of mechanical forces on cell viability is of great importance when growing the cells in agitated systems. By far the greatest amount of work reported in the literature has been done on suspension cells but adherent cells also experience shear forces not only in bioreactors also in vivo. Therefore, most research has be done on endothelial cells but studies exists done on non-endothelial cells. The influence of shear forces on cell growth, morphology and productivity will be discussed as well as possibilities of making the cells more resistant. 

Soule et al. [141] constructed a sparged, concentric cylinder bioreactor for the cultivation of suspensions of Pirus malus. Growth was reduced under all rotational conditions. Sun and Linden [106] employed a rotating wall vessel (Rotary Cell Culture System, Synthecon, Houston, TX, USA) to cultivate suspensions of Taxus cuspidata under laminar flow conditions. Shear rates were... 

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