Methods for Oxygenation of Continuous Cultures of Brewer’s Yeast, Saccharomyces cerevisiae

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.

Microbial Factories and Exploiting Synergies of Bioreactor Technologies to Produce Bioproducts

“…The internal volume of the membrane was 8.0 mL, and with tubing and pumps, the total volume of each bioreactor was 10 mL. The membranes were highly effective chambers for growing cells and for gas exchange of CO 2 and O 2 [74]. Prior to the experiment, tubing and glassware were autoclaved at 121 • C and 1034 mbar (15 psi) for 20 min and assembled under a laminar flow hood.…”

“…where N corresponds to cell biomass at times t i+1 and t i , where t i+1 − t i are the time periods of abrupt changes in biomass trends. The oxygen transfer rate, K L a, of the hollow-fiber filters was calculated by Granata et al [74] as…”

“…where Q is the fluid flow rate through the membrane (43 L d −1 ); DO Br is the oxygen concentration in the bioreactor in mg L −1 ; DO s is the saturated oxygen concentration in mg L −1 , and A is the surface area of the membrane (100 cm 2 ). The K L a of the membrane was 1872 d −1 [74].…”

Micro-Bioreactors in Space: Case Study of a Yeast (Saccharomyces cerevisiae) Bioreactor With a Non-Invasive Monitoring Method

“…Generally, hollow fiber filters have high oxygen transfer rates (Granata et al, 2021). PDMS filters have been shown to have higher oxygen transport rates than stirred reactors at lower shear rates (Orgill et al, 1996).…”