A Review of Dissolved Oxygen Concentration Measurement Methods for Biological Fermentations (original) (raw)
Related papers
Measurement of oxygen solubility in fermentation media: A colorimetric method
Biotechnology and Bioengineering, 1989
Methods of measuring oxygen solubility in culture media are scarce, and those available are tedious to apply. A simple colorimetric assay was developed and applied to the analysis of oxygen solubility during alcoholic fermentation. The method was based on the consumption of oxygen by glucose oxidase activity and the production of the pink quinone of syringaldazine by coupled peroxidase activity. Color formation at 526 nm progressed through an optimum that was a linear function of the oxygen added to the assay. Sensitivity was maximized by operating at pH 7 and limiting the medium sample volume added. Each assay took 10-15 min to prepare and react. Reaction time was minimized by using abundant glucose and enzyme concentrations. Data obtained by the assay developed showed good agreement with published oxygen solubilities in water and selected media at various temperatures. Subsequent analyses of fermentation broths indicated falling sugar concentration to be primarily responsible for increases in oxygen solubility during fermentation. For example, during fermentations started with 230 giL xylose or glucose, oxygen solubility could increase by 41 % due to sugar consumption alone. This procedure can provide the solubility data needed to accurately calibrate in-line electronic probes for monitoring dissolved oxygen concentration during fermentation processes. * The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.
A biosensor was developed for the determination of BOD value of fermentation industry effluent. e developed biosensor was fabricated by immobilizing the microbial consortium on cellulose acetate (CA) membrane in close proximity to a DO probe electrode. e microbial consortium was harvested from the fermentation industry effluent. e BOD biosensor was calibrated by using a solution containing the equivalent amount of glucose/glutamic acid (GGA) as a standard sample solution. e response time was optimized by immobilizing different concentrations of cell biomass on CA membrane. Once the response time was optimized, it was used for determination of BOD of fermentation industry effluent. For analysis of fermentation industry effluent, the response time was observed 7 minutes with detection limit 1 mg/L. Good linear range with GGA standard solution was observed, 2 0.99 with relative standard deviation (RSD) < 9%. e observed BOD value by biosensor showed a good comparison with the conventional method for the determination of BOD.
Noninvasive measurement of dissolved oxygen in shake flasks
Biotechnology and Bioengineering, 2002
Shake flasks are ubiquitous in cell culture and fermentation. However, conventional devices for measuring oxygen concentrations are impractical in these systems. Thus, there is no definitive information on the oxygen supply of growing cells. Here we report the noninvasive, nonintrusive monitoring of dissolved oxygen (DO) in shake flasks using a low-cost optical sensor. The oxygen-sensitive element is a thin, luminescent patch affixed to the inside bottom of the flask. The sensitivity and accuracy of this device is maximal up to 60% DO, within the range that is critical to cell culture applications. By measuring actual oxygen levels every 1 or 5 min throughout the course of yeast and E. coli fermentations, we found that a modest increase in shaker speed and a decrease in culture volume slowed the onset of oxygen limitation and reduced its duration. This is the first time that in situ oxygen limitation is reported in shake flasks. The same data is unattainable with a Clark type electrode because the presence of the intrusive probe itself changes the actual conditions. Available fiber optic oxygen sensors require cumbersome external connections and recalibration when autoclaved.
Biotechnology and Bioengineering, 1982
The role of computers in the monitoring and control of fermentation processes has increased steadfastly. The ultimate utility of the machines will not only depend on the availability of online sensors but also on the availability of techniques that combine direct measurements, leading towards estimates of variables closely related to the microbial process or its control. In this article, a methodology for on-line and noninterfering evaluation of the volumetric mass-transfer coefficient R,a is developed. A detailed presentation of the procedure. called "the static method," is given. Its feasibility is proved through implementation of the method on an antibiotic fermentation process. These experiments indicate that operator actions meant to modify the oxygen-transfer conditions can be checked on-line. The quantitative value of the static method is ascertained by comparing the experimental results with the R,a estimates obtained with the "gassing-out" method. A sensitivity analysis was carried out, revealing the need for temperature and pressure corrections and showing that the precision of the oxygen analyzer determines the precision of the static method.
Oxygen solubilities in fermentation fluids
European Journal of Applied Microbiology and Biotechnology, 1979
Fermentation media consist of a large number of chemicals whose composition undergoes alteration during the course of fermentation. As a result of this, conventional methods and correlations for oxygen solubility measurement and prediction do not apply in these systems. Using a physical method, oxygen solubilities were measured in simulated chemical systems and in fermentation broths. Sugars, salts, and fermentation products were identified as major factors influencing oxygen solubility. Salt effect was correlated with electrical conductivity of the medium, which was easy to measure during fermentation. For mixtures and for fermentation medium, individual influences were found to be log-additive in accordance with Danckwerts (1970).
Biotechnology and Bioengineering, 1989
Water activity of the substrate is an important and acute factor for growth a s well a s for metabolic production of microorganisms or for biocatalyst systems. A sensor has been designed in order t o control this parameter on-line during submerged and solid-substrate fermentations. This sterilizable sensor allows the measurement of the relative humidity of t h e atmosphere in a small chamber by means of a capacitive element separated from t h e medium by a thin ethylenepolytetrafluoride membrane. For high a, values (>0.90) a sequential circulation of a dried g a s prevents the sensor saturation. Measurements a r e rapid and accurate, and control of the water activity of a fermentation medium has been carried out for 5 days using this sensor.
Biotechnology and Bioengineering, 2004
For long-term growth of mammalian cells in perfused bioreactors, it is essential to monitor the concentration of dissolved oxygen (DO) present in the culture medium to ascertain the health of the cells. An optical oxygen sensor based on dynamic fluorescent quenching was developed for long-term continuous measurement of DO for NASA-designed rotating perfused bioreactors. Tris(4,7diphenyl-1,10-phenanthroline) ruthenium(II) chloride is employed as the fluorescent dye indicator. A pulsed, blue LED was chosen as the excitation light source. The sensor can be sterilized using an autoclave. The sensors were tested in a perfused rotating bioreactor supporting a BHK-21 (baby hamster kidney) cell culture over one 28-day, one 43-day, and one 180-day cell runs. The sensors were initially calibrated in sterile phosphate-buffered saline (PBS) against a blood-gas analyzer (BGA), and then used continuously during the entire cell culture without recalibration. In the 180-day cell run, two oxygen sensors were employed; one interfaced at the outlet of the bioreactor and the other at the inlet of the bioreactor. The DO concentrations determined by both sensors were compared with those sampled and measured regularly with the BGA reference. The sensor outputs were found to correlate well with the BGA data throughout the experiment using a single calibration, where the DO of the culture medium varied between 25 and 60 mm Hg at the bioreactor outlet and 80-116 mm Hg at the bioreactor inlet. During all 180 days of culture, the precision and the bias were F 5.1 mm Hg and À 3.8 mm Hg at the bioreactor outlet, and F 19 mm Hg and À 18 mm Hg at inlet. The sensor dynamic range is between 0 and 200 mm Hg and the response time is less than 1 minute. The resolution of the sensor is 0.1 mm Hg at 50 mm Hg, and 0.25 mm Hg at 130 mm Hg.
Methods for Oxygenation of Continuous Cultures of Brewer’s Yeast, Saccharomyces cerevisiae
Fermentation
Maintaining steady-state, aerobic cultures of yeast in a bioreactor depends on the configuration of the bioreactor system as well as the growth medium used. In this paper, we compare several conventional aeration methods with newer filter methods using a novel optical sensor array to monitor dissolved oxygen, pH, and biomass. With conventional methods, only a continuously stirred tank reactor configuration gave high aeration rates for cultures in yeast extract peptone dextrose (YPD) medium. For filters technologies, only a polydimethylsiloxan filter provided sufficient aeration of yeast cultures. Further, using the polydimethylsiloxan filter, the YPD medium gave inferior oxygenation rates of yeast compared to superior results with Synthetic Complete medium. It was found that the YPD medium itself, not the yeast cells, interfered with the filter giving the low oxygen transfer rates based on the volumetric transfer coefficient (KLa). The results are discussed for implications of minia...