Dissolved oxygen tension

Biomass formation and transamination activity within the cells develop in a similar manner. Growth usually continues until limited by the availability of dissolved oxygen tension (DOT). After 10-15 hours a dry weight biomass concentration of 10 g V is normally reached. 

To perform fed-batch experiments with P. putida a method had to be developed to prevent carbon limitation and to prevent a buildup of the concentration of the fatty acids to inhibitory levels. HPLC methods to measure the concentration of aliphatic substrates and octanoic acid have been reported, but these are not suitable for the detection of long chain fatty acids in a watery phase due to their low solubility. Instead Huijberts et al. [55, 56] developed a method in which discrete pulses of fatty acids were added to fed-batch cultures. Substrate exhaustion was detected by a sudden increase in dissolved oxygen tension and this signal was used to trigger the injection of another fatty acid pulse into the... 

In transgenic hairy root cultures, the concentration of IgG antibody in the biomass increased by 52% relative to the levels obtained under air when the roots were cultured at a dissolved oxygen tension of 150% air saturation [17]. Compared with root cultures grown at 50% air saturation, which is a realistic operating dissolved oxygen tension in poorly mixed, large-scale root reactors, oxygen enrichment to 150% air saturation improved total antibody accumulation 2.9-fold. 

Viliesid F, Lilly MD (1992) Influence of dissolved oxygen tension on the synthesis of catechol 1, 2-dioxygenase by Pseudomonas putida. Enzyme Microb Technol 14 561-565... 

SMITH, M.P.W. and EVANS, M.R. (1982). The effects of low dissolved oxygen tension during the aerobic treatment of piggery slurry in completely mixed reactors. J. appl. Bact. 53,117-126... 

Figure 15.9 shows that this approach worked quite nicely the substrate was added to a total concentration of 2.5 g/L, but neither substrate nor product accumulated in the bioreactor medium. Without a product recovery loop the product concentration (3-phenylcatechol) did not exceed 0.4 g/L, because of biocatalyst deactivation (results not shown). With the loop, 2-phenylphenol and 3-phenylcatechol concentrations remained below 0.1 g/L. Therefore, cell viability and biocatalytic activity were maintained, as indicated by the constantly low dissolved oxygen tension in the aerated reactor. As a result product yields (based on the 3-phenylcatechol eluted from the product sink) increased by one order of magnitude." ... 

The dissolved oxygen tension (DOT), feed rate and KOH consumption were monitored. When the cell density reached an OD6oo= 1,IPTG(1 mL, 100 him) was added to induce the CPDMO expression. 

There have been misconceptions among some researchers regarding the influence of the dissolved oxygen tension (DO) in baculovirus infection and product expression, as often no distinction is made between dissolved oxygen tension and oxygen limitations in mass transfer. The analysis of the effects of DO levels can only be studied effectively in bioreactors with controlled DO levels [56]. 

The bioprocess analyst has long realised that the more (useful) measurements we can make the more likely are we to understand our bioprocesses, and we ourselves have long sought to increase the number of non-invasive, on-line probes available [9,10]. Classical methods, monitoring factors such as pH, dissolved oxygen tension, and so on, however, are in essence univariate methods, and only give information on individual determinands. 

Cell circulation may be enhanced with a mechanical stirring device to minimize the necessary sparging rate at low cell densities to a level sufficient to maintain dissolved oxygen tension at the desired level... 

At cell densities exceeding 5 x 10 mL in the NLF 22 bioreactor, the dissolved oxygen tension had to be maintained by intermittently sparging O2 directly into the culture and raising the stirrer speed from 100 rpm (impeller tip speed 0.8 m s ) to 150 rpm (tip speed 1.2 m s ). No negative effects on cell growth and viability were observed. 

Frykman, S.A., Tsuruta, H., Starks, C.M., Regentin, R. et al. (2002) Control of secondary metabolite congener distributions via modulation of the dissolved oxygen tension. Biotechnol. ProgK, 18 (5), 913-920,... 

Kubicek C, Zehentgruber O, El-Kalak H, Rohr M. Regulation of citric acid production by oxygen effect of dissolved oxygen tension on adenylate levels and respiration in Aspergillus niger. Eur J Appl Microbiol Biotechnol 1980 9 101-15. 

Kendrick, A. and Ratledge, C. (1992a) Lipid formation in the oleaginous mould Entomoph-thora exitalis grown in continuous culture effects of growth rate, temperature and dissolved oxygen tension on polyunsaturated fatty adds. Appl. Microbiol. Biotechnol. yj, 18-22. 

Lara, A.R., Leal, L.I., Flores, N., Gosset, G. et al (2006) Transcriptional and metabolic response of recombinant Escherichia coli to spatial dissolved oxygen tension gradients simulated in a scale-down system. Biotechnol Bioeng., 93 (2), 373-385. 

Cortes, G., Trujillo-Roldan, MA, Ramirez, O.T., and Galindo, E. (2005) Production of galactosidase by Kluyveromyces marxianus under oscillating dissolved oxygen tension. Process Biochem., 40 (2), 773-778. 

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