Culture pH (culture + ph)

Distribution by Scientific Domains


Selected Abstracts


A predictive high-throughput scale-down model of monoclonal antibody production in CHO cells

BIOTECHNOLOGY & BIOENGINEERING, Issue 6 2009
Rachel Legmann
Abstract Multi-factorial experimentation is essential in understanding the link between mammalian cell culture conditions and the glycoprotein product of any biomanufacturing process. This understanding is increasingly demanded as bioprocess development is influenced by the Quality by Design paradigm. We have developed a system that allows hundreds of micro-bioreactors to be run in parallel under controlled conditions, enabling factorial experiments of much larger scope than is possible with traditional systems. A high-throughput analytics workflow was also developed using commercially available instruments to obtain product quality information for each cell culture condition. The micro-bioreactor system was tested by executing a factorial experiment varying four process parameters: pH, dissolved oxygen, feed supplement rate, and reduced glutathione level. A total of 180 micro-bioreactors were run for 2 weeks during this DOE experiment to assess this scaled down micro-bioreactor system as a high-throughput tool for process development. Online measurements of pH, dissolved oxygen, and optical density were complemented by offline measurements of glucose, viability, titer, and product quality. Model accuracy was assessed by regressing the micro-bioreactor results with those obtained in conventional 3,L bioreactors. Excellent agreement was observed between the micro-bioreactor and the bench-top bioreactor. The micro-bioreactor results were further analyzed to link parameter manipulations to process outcomes via leverage plots, and to examine the interactions between process parameters. The results show that feed supplement rate has a significant effect (P,<,0.05) on all performance metrics with higher feed rates resulting in greater cell mass and product titer. Culture pH impacted terminal integrated viable cell concentration, titer and intact immunoglobulin G titer, with better results obtained at the lower pH set point. The results demonstrate that a micro-scale system can be an excellent model of larger scale systems, while providing data sets broader and deeper than are available by traditional methods. Biotechnol. Bioeng. 2009; 104: 1107,1120. © 2009 Wiley Periodicals, Inc. [source]


Impact of nutritional supplements and monosaccharides on growth, oxalate accumulation, and culture pH by Sclerotinia sclerotiorum

FEMS MICROBIOLOGY LETTERS, Issue 1 2007
Bryan J. Culbertson
Abstract Sclerotinia sclerotiorum D-E7 was studied to determine the impact of nutritional supplements and monosaccharides on growth, oxalate accumulation, and culture pH in broth media (initial pH c. 5). Cultures with 0.1% nutritional supplement (tryptone, yeast extract, or soytone) yielded minimal growth, 2,3 mM oxalate, and a final culture pH of 4.2,4.8. In contrast, cultures with 0.1% nutritional supplement and 25 mM glucose yielded significant growth, minimal oxalate (<1 mM), and a final culture pH of 2.8,3.7. Similar trends were observed when glucose in 0.1% soytone cultures was replaced with 25 mM d -mannose, l -arabinose, or d -xylose. With 1% soytone-25 mM glucose cultures, growth and oxalate accumulation (,21 mM) occurred with little change in initial pH. This was not the case with 1% soytone-250 mM glucose cultures; increased glucose levels resulted in a decrease in oxalate accumulation (,7 mM) and in final culture pH (3.4). Time-course studies with these cultures revealed that oxalate accumulation was suppressed during growth when the culture pH dropped to <4. Overall, these results indicate that (1) the decrease in external pH (i.e. acidification) was independent of oxalate accumulation and (2) acidification coupled to glucose-dependent growth regulated oxalate accumulation by Sclerotinia sclerotiorum. [source]


A Cyclical Semicontinuous Process for Production of Human ,1 -Antitrypsin Using Metabolically Induced Plant Cell Suspension Cultures

BIOTECHNOLOGY PROGRESS, Issue 2 2005
Melody M. Trexler
Transgenic rice suspension cultures were utilized to produce a human therapeutic protein, recombinant ,1 -antitrypsin (rAAT), in a cyclical, semicontinuous operation. Recombinant protein production was induced by removing the carbon source from the cell culture medium. The transgenic rice cells secreted the rAAT into the medium, and therefore medium exchanges could be performed for consecutive growth and protein expression phases. The process consisted of three cycles over a 25,28 day period, with growth phases lasting 4,6 days each and protein expression phases lasting 2.5,5 days each. Biomass and sugar concentrations, oxygen uptake rate, cell viability, culture pH, total extracellular protein, and active rAAT were measured throughout the cyclical process. The data profiles were reproducible between separate cyclical runs where, following each induction period, cell growth and viability could be reestablished once sucrose was added back to the culture. Volumetric productivities ranged from 3 to 12 mg active rAAT/(L day) for individual cycles with overall volumetric productivities of 4.5 and 7.7 mg active rAAT/(L day). [source]


Measurement and Control of Dissolved Carbon Dioxide in Mammalian Cell Culture Processes Using an in Situ Fiber Optic Chemical Sensor

BIOTECHNOLOGY PROGRESS, Issue 5 2000
Robert N. Pattison
At high viable cell concentrations in large-scale mammalian cell culture processes, the accumulation of dissolved carbon dioxide (dCO2, typically quantified as an equilibrium gas-phase concentration) becomes problematic as a result of low CO2 removal rates at reduced surface-to-volume ratios. High dCO2 concentrations have previously been shown to inhibit cell growth and product formation in mammalian cells and to alter the glycosylation pattern of recombinant proteins. Therefore, reliable monitoring and control of dCO2 are important for successful large-scale operation. Off-line measurements by instruments such as blood gas analyzers (BGA) are constrained by the low frequency of data collection and cannot be used for on-line control. In a preliminary evaluation of the YSI 8500 in situ sensor, a response time (t90%) of 6 min, sensitivity of 0.5% CO2 (3.6 mmHg), and linearity of measurement (R2 = 0.9997) between the equivalent gas-phase partial pressure of 0,180 mmHg (0% and 25% CO2) were established. Measurements were found to be unaffected by culture pH and typical mammalian cell culture concentrations of glucose, glutamine, glutamate, lactate, and ammonium. The sensor withstood repeated sterilization and cleaning cycles. The reliability of this sensor was demonstrated in microcarrier-based Chinese hamster ovary (CHO) cell perfusion cultures at reactor scales of 30, 40, 340, and 2000 L and was successfully implemented in a dCO2 control strategy using N2 sparging. [source]