Abstract
BackgroundShake flasks are widely used because of their low price and simple handling. Many researcher are, however, not aware of the physiological consequences of oxygen limitation and substrate overflow metabolism that occur in shake flasks. Availability of a wireless measuring system brings the possibilities for quality control and design of cultivation conditions.ResultsHere we present a new wireless solution for the measurement of pH and oxygen from shake flasks with standard sensors, which allows data transmission over a distance of more than 100 metres in laboratory environments. This new system was applied to monitoring of cultivation conditions in shake flasks. The at-time monitoring of the growth conditions became possible by simple means. Here we demonstrate that with typical protocols E. coli shake flask cultures run into severe oxygen limitation and the medium is strongly acidified. Additionally the strength of the new system is demonstrated by continuous monitoring of the oxygen level in methanol-fed Pichia pastoris shake flask cultures, which allows the optimisation of substrate feeding for preventing starvation or methanol overfeed. 40 % higher cell density was obtained by preventing starvation phases which occur in standard shake flask protocols by adding methanol when the respiration activity decreased in the cultures.ConclusionThe here introduced wireless system can read parallel sensor data over long distances from shake flasks that are under vigorous shaking in cultivation rooms or closed incubators. The presented technology allows centralised monitoring of decentralised targets. It is useful for the monitoring of pH and dissolved oxygen in shake flask cultures. It is not limited to standard sensors, but can be easily adopted to new types of sensors and measurement places (e.g., new sensor points in large-scale bioreactors).
Highlights
IntroductionNot aware of the physiological consequences of oxygen limitation and substrate overflow metabolism that occur in shake flasks
Shake flasks are widely used because of their low price and simple handling
In this paper we demonstrate for the advances of the SENBIT technology for monitoring physiological events in shake flasks at the example of pH and oxygen changes in E. coli cultures and the possibilities for process optimisation at the examples of the critical feeding of methanol in cultures of Pichia pastoris
Summary
Not aware of the physiological consequences of oxygen limitation and substrate overflow metabolism that occur in shake flasks. Shake flask cultivation is an easy way to grow small amounts of microbes. They are applied for bioprocess optimization and for preparation of starter cultures for bioreactor cultivations. Due to non-limited growth anaerobic conditions emerge because shaking can not provide enough oxygen for fast-growing microbes in dense cultures. The availability of high concentration of glucose in shake flask enhances synthesis of overflow metabolites, since the capacities of the respiratory system and citric acid cycle can not process all the glucose taken into the cell. Cell and product yields may vary very much between shake flask cultivations. The reasons for poor reproducibility can not be recognised without monitoring
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