Abstract
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 miniaturized bioreactors in low-gravity environments.
Highlights
Fermentation 2021, 7, 282. https://Many experiments conducted with Brewer’s yeast, Saccharomyces cerevisiae, use batch and continuous cultures to rear cells in growth medium
Since the optical spots were mounted to the bottom of the bioreactor chamber, a stir bar would have interfered with data acquisition and could not be used as a means for oxygen transfer
The KL a values for the steady-state impeller/yeast extract peptone dextrose (YPD) and the PDMS SC methods were in the same range as most bioreactor aeration processes using yeast media and de-ionizer water
Summary
Fermentation 2021, 7, 282. https://Many experiments conducted with Brewer’s yeast, Saccharomyces cerevisiae, use batch and continuous cultures to rear cells in growth medium. Common methods for aerating yeast cultures are bubbling, shaking, or stirring, which promotes oxygen transfer into the culture through the free surface while newer methods use filters for aeration [1]. Some of these methods pose problems, such as the use of commercially available yeast extract peptone dextrose (YPD) medium which foams when bubbled constantly or intermittently and may oxidize compounds in the medium. Head space, and shaking and stirring of cultures, are not feasible, nor is bubbling medium with air or oxygen [3]. Critical is a small system size since the payload is limited [3]
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