Cultivation fed-batch

Fig. 1. Fed-batch cultivation of P. notoginseng cells in 30-L CIB. Symbols DW ( ), SOUR (x), residual sugar ( ), saponin content (A) and production (A), and polysaccharide content (o) and production ( ).

A high level of poly(3HB) accumulation is also obtained if the cells are grown under carbon substrate limitation, and the cultivation in the second fermenter is also carried out under carbon limitation. In this case, a substrate flow rate (F2) below that corresponding to the maximum specific poly(3HB) formation rate should be chosen [114]. This cultivation strategy is especially convenient when using toxic substrates like acetic acid. Low substrate concentrations are more conveniently maintained in continuous cultivation than in fed-batch cultivation. The only additional equipment needed is a system to ensure constant working volumes and flow rates. 

The effect of various organic acids on growth of IGTS8 was studied by Honda et al. [187]. This was the first study looking at fed-batch cultivation of IGTS8 cells. 

Procedure 3 Batch and Fed-batch Cultivation of Recombinant E. coli JMlOl (pSPZlO) ... 

Due to the complexity of bioprocesses, and the lack of direct in-process measurements of critical process variables, much work is being done on development of soft sensors and model predictive control of such systems. Soft sensors have long been used to estimate biomass concentration in fed-batch cultivations. The soft sensors can be integrated into automated control structures to control the biomass growth in the fermentation. 

Phenylethanol L-Phenylalanine Diverse yeasts e.g. Saccharomyces and Kluyveromyces >10gL , 30 h, 0.5-1 tyear Fed-batch cultivation in situ product recovery by two-phase system with more than 25 g L in the organic phase possible [109,120]... 

Fed-batch cultivation -Organic phase polypropylene glycol 1200... 

Immobilisation of an Acetobacter aceti strain in calcium alginate resulted in improvement of the operational stability, substrate tolerance and specific activity of the cells and 23 g phenylacetic acid was produced within 9 days of fed-batch cultivation in an airlift bioreactor [133]. Lyophilised mycelia of Aspergillus oryzae and Rhizopus oryzae have been shown to efficiently catalyse ester formation with phenylacetic acid and phenylpropanoic acid and different short-chain alkanols in organic solvent media owing to their carboxylesterase activities [134, 135] (Scheme 23.8). For instance, in n-heptane with 35 mM acid and 70 mM alcohol, the formation of ethyl acetate and propylphenyl acetate was less effective (60 and 65% conversion yield) than if alcohols with increased chain lengths were used (1-butanol 85%, 3-methyl-l-butanol 86%, 1-pentanol 91%, 1-hexanol 100%). This effect was explained by a higher chemical affinity of the longer-chain alcohols, which are more hydrophobic, to the solvent. 

The RQ control, where the sugar-feeding rate is controlled so as to maintain the RQ value at approximately 1.0, is the distinct control method in aerobic fed-batch cultivation such as with baker s yeast production. By keeping the RQ at 1.0 during the fed-batch operation, cell production with a high yield will be achieved. 

When an NHg solution is used as a nitrogen source of fermentation, the consumption of NHg decreases the pH of the culture broth. A pH stat control utilizes the pH change as a process variable where the NHg addition is manipulated so as to keep the pH value constant during fermentation. The pH stat is often employed in a fed-batch cultivation of industrial glutamic acid production (high NHg consuming fermentation) using molasses as a feedstock. 

P de Noronha Pissara, J Nielsen, MJ Bazin. Pathway kinetics and metabolic control analysis of a high-yielding strain of Penicillium chrysogenum during fed-batch cultivations. Biotechnol Bioeng 51 168-176, 1996. 

Fed-batch cultivation (A) operational configuration and typical volume, cell, and substrate profiles, for a pulse feeding strategy (B) concentration of cells, product, and two substrates in a fed-batch bioreactor culture of a myeloid transfectoma producing a humanized monoclonal antibody (Center of Molecular Immunology-CIM, Cuba). 

Figure 9.19 shows typical cell concentrations reached in the main industrial bioreactors and a comparison of these values with those found in microbial fermentations. As can be observed, batch and fed-batch cultivations attain dry biomass values comparable to those of continuous cultures of microorganisms, so that mass and heat transfer capacities are not limited for these operation modes. However, high cell density cultivation in heterogeneous bioreactors, such as hollow-fiber devices, reaches dry biomass values similar to the maxima observed in microbial cultures. 

Altamirano C, Paredes C, Illanes A, Cairo JJ, Godia F (2004), Strategies for fed-batch cultivation of t-PA producing CFIO cells substitution of glucose and glutamine and rational design of culture medium, J. Biotechnol. 110 171-179. 

Xie L, Wang DIC (2006), Fed-batch cultivation of animal cells using different medium design concepts and feeding strategies, Biotechnol. Bioeng. 95 270-284. 

Fig. 5. Time profiles of A fresh and dry cell weights, medium sugar and SOUR, B the content and total production of ginseng saponin and C polysaccharide in fed-batch cultivation of Panax notoginseng cells in 1-1 airlift reactors. The arrow in A indicates the sucrose feeding point. The error bars in the figure indicate the standard deviations for the samples of three identical reactors. Symbols A Dark circles FW open circles DW open triangles, medium sugar dark triangles, SOUR. B Dark circles Saponin production open circles saponin content. C Dark circles Polysaccharide production open circles polysaccharide content...

Because of the need to avoid mutations and maintain the superior qualities of the genetically developed strain, batch or fed-batch operations are used in most applications. Continuous culture operations, however, provide a time-invariant environment that facilitates greatly the study of a biological process in research laboratories. Moreover, some industrial operations employ continuous reactors, such as the single-cell protein facility of ICI in Billingham, England (total reactor volume of about 2,300 m3), all waste treatment processes, and others. It should be noted that it is relatively common to follow a batch process with a period of fed-batch or continuous operation. Also, in most cases batch cultivation is the optimal start-up procedure for continuous or fed-batch cultivation (Yamane et al, 1977). 

Figure 5 shows on-line-data of sucrose concentrations and the enzyme production rate obtained during a fed-batch cultivation. Obviously, sucrose concentration and enzyme activity correlate. Due to growth of the microorganisms, sucrose concentration decreases in the first five hours. After a lag, subtilisin is produced at an optimum rate. The enzyme activity decreases after that because the sucrose concentration is too low of a limited. Thus, sucrose is fed to the medium and subtilisin production increases again. 

C Undey, E Tatara, and A Cinar. Intelligent real-time performance monitoring and quality prediction for batch/fed-batch cultivations. J. Biotechnology, 108(l) 61-77, 2004. 

Benzaldehyde can be produced from benzoyl formate with whole cells of Pseudomonas putida ATCC 12633 as biocatalyst119 201 (Fig. 16.6-5). Alternatively, but less effectively, mandelic acid can be used as starting material. A pH of 5.4 was found to be optimal for benzaldehyde accumulation. At this proton concentration, partial inactivation of the benzaldehyde dehydrogenase isoenzymes and activation of the benzoyl formate decarboxylase are reported. Fed-batch cultivation prevented substrate inhibition. In situ product removal is necessary to prevent product inhibition. 

Franz, C., Kern, J., Pdtschacher, F. and Bayer, K. (2005) Sensor combination and chemomet-ric modelling for improved process monitoring in recombinant E. coli fed-batch cultivations. JBiotechnol, 120 (2), 183-196. 

Fed-batch fermentations with P. pastoris ocMnPl-1 were performed using 3.0-1 BioFlo 100 fermentors (New Brunswick Scientific Co. Inc.). The suspended cell, fed-batch cultivation was divided into two stages batch and fed-batch cultivation with glucose. P. pastoris aMnPl-1 inoculum cultures (100 ml) were grown in YPD medium and used to inoculate 1 1 of medium in the bioreactors. 

Cleland, N., Enfors, S.-0., Control of Glucose-Fed Batch Cultivations of E. coli by Means of an Oxygen Stabilized Enzyme Electrode , Eur. J. Appl. Microbiol. Biotechnol. 18 (1983) 141-147. 

The problems of adequate sampling are obvious upon examination of Figures 22-11 and 22-12. In both cases, an enzyme thermistor was used for quasi on-line glucose determination of a fed-batch cultivation of Cephalosporium acremonium [86]. Sampling was performed by micro- or ultraflltration. Only the analysis of ultraflltered samples shows good agreement between enzyme thermistor and off-line data. 

Figure 22-11. Monitoring of glucose with an enzyme thermistor during a fed-batch cultivation of C. acremonium. Samples were withdrawn from the fermenter via a microfiltration probe. ( Yellow Springs glucose analyzer data, A enzyme thermistor data).

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