Squalene versus Ergosterol Formation Using Saccharomyces cerevisiae: Combined Effect of Oxygen Supply, Inoculum Size, and Fermentation Time on Yield and Selectivity of the Bioprocess

Abstract

The dynamics of two wild type strains of Saccharomyces cerevisiae (BY4741 and EGY48) that vary in the ability to produce sterols were compared in batch cultures under different aeration conditions. Poor supply of oxygen enhanced selectivity of the bioprocess in favor of squalene formation. Optimization of inoculum size and fermentation time arranged according to a central composite statistical design revealed significant differences between the strains in terms of yield and productivity. Experimental verification showed that an optimized bioprocess under semianaerobic conditions is competitive with regard to those reported in the literature. Maximum squalene yield and productivity were, respectively, 2967.6 +/- 118.7 microg/L of culture medium and 104 +/- 4.2 microg/Lh for BY4741 and 3129 +/- 109.5 microg/L of culture medium and 155.9 +/- 5.5 microg/Lh for EGY48. The prospect of developing high-purity squalene preparations that meet food safety regulation demands is expected to attract the interest of the food industry.

Overproduction of squalene synergistically downregulates ethanol production in Saccharomyces cerevisiae

“…Plants and microbes have also been used for overproduction of squalene, but none are viable for industrial scale production of squalene because these methods are limited in yielding sufficient quantities. Indeed, the approximate amount of squalene produced by plants, yeasts and thraustochytrids ranged from 1 to 61 mg/g dry cell weight (DCW) ( Han-Ping H, 2002), <0.43-0.70 mg/g DCW (Chang MH, 2008;Mantzouridou F, 2009) and 0.1-0.38 mg/g DCW (Chen G, 2010;Fan KW, 2010;Li Q, 2009), respectively.…”

Differences in stationary-phase cells of a commercial Saccharomyces cerevisiae wine yeast grown in aerobic and microaerophilic batch cultures assessed by electric particle analysis, light diffraction and flow cytometry

“…Distribution shapes could be explained by the existence of heterogeneous populations known as quiescent and non-quiescent cells [2]. Under aerobic conditions, the oxygen concentration decreases along the log phase despite the magnetic stirring, and the sample reaches the stationary phase with lower oxygen concentration [18,22]. These environmental changes, in addition to nutrient depletion and pH changes, affect the physiology of yeast that changes from respirofermentative to fermentative [33].…”

“…Both aerobic and anaerobic growing conditions have importance at the industrial level for production of bioethanol, cell biomass and proteins, among other substances, for example squalene and b-glucan [9,18]. Comprehension of respirofermentative growth is important to optimise the different biotechnological processes in which this yeast is involved.…”

Engineering of the terpenoid pathway in Saccharomyces cerevisiae co-overproduces squalene and the non-terpenoid compound oleic acid

“…Researchers have thoroughly screened plant and microbial sources for the potential capacity to produce high levels of squalene, but because of their limited squalene production capacity, none of them have been suitable for large-scale production. For example, the production of squalene in plants, yeasts and thraustochytrids was estimated to be only 1-61 mg g -1 dry cell weight (DCW) (He HP, 2002), <0.43-0.70 mg g -1 DCW (Chang MH, 2008;Mantzouridou F, 2009) and 0.1-0.38 mg g -1 DCW (Chen G, 2010;Fan KW, 2010;Li Q, 2009), respectively.…”