Enhancement of ergosterol production by Saccharomyces cerevisiae in batch and fed-batch fermentation processes using n-dodecane as oxygen-vector

The effect of n-dodecane used as oxygen-vector in batch and fed-batch fermentations of S. cerevisiae for producing ergosterol has been comparatively investigated. Regardless of n-dodecane concentration, the results indicated the increase for about three times of ergosterol content inside the yeasts cells in fed-batch process. In both fermentation systems, by adding the oxygen-vector, the ergosterol concentration increased with over 50%. The oxygen-vector concentration corresponding to the maximum level of ergosterol depended mainly on biomass concentration, being 5% vol. for batch fermentation, and 10% vol. for fed-batch one. The increase of biomass concentration in the fed-batch process partially affected the positive influence of oxygen-vector, effect that became less significant only for hydrocarbon concentration over 10% vol. The inhibitory phenomenon induced at higher concentration of hydrocarbon also limits the positive influence of oxygen-vector, but this effect was partially counteracted in the fed-batch process due to the higher amount of yeasts biomass produced.