Comparative Analysis of Squalene Production in Cystobasidium benthicum and Saccharomyces cerevisiae

Background and Objectives Squalene is a versatile linear polyunsaturated triterpenoid with diverse applications in the cosmetic and pharmaceutical industries. It can be used as a vaccine adjuvant component, a nutritional supplement, and an antioxidant. Yeast cells have a great potential to serve as a source for squalene production. This investigation aims to evaluate the content of squalene in two yeast strains: Cystobasidium benthicum, isolated from beaches of Qeshm Island, and Saccharomyces cerevisiae, in the presence of terbinafine as an inhibitor, and at different temperatures. Materials and Methods Wild-Type Saccharomyces cerevisiae and native Cystobasidium benthicum cells were cultured in a medium containing glucose, yeast extract, and a nitrogen compound. Terbinafine, an inhibitor of ergosterol biosynthesis, was added to the culture medium at concentrations ranging from ۰.۰۲ to ۰.۵۵ mM. Biomass formation and squalene content in these yeasts were analyzed after ۲۴, ۴۸, ۷۲, and ۹۶ hours of fermentation. To analyze the effect of temperature on squalene production, these yeasts were cultivated at temperatures ranging from ۱۰°C to ۳۵°C. All experiments were performed in biological triplicates. Results and Discussion In the absence of the inhibitor, Saccharomyces cerevisiae and Cystobasidium benthicum produced squalene at rates of ۱.۶ and ۰.۱۲ mg/g dry cell weight (DCW), respectively. Terbinafine affected the biosynthesis of squalene in both yeast strains. Maximum squalene content in Saccharomyces cerevisiae (۱۰.۰۲ ± ۰.۵۳ mg/g DCW) and squalene yield (۲۰.۷۰ ± ۱.۰۰ mg/L) were achieved using ۰.۴۴۲ mM terbinafine after ۲۸ hours and ۰.۳۰۰ mM terbinafine after ۳۰ hours, respectively. Maximum squalene content in Cystobasidium benthicum (۱۱.۳۲± ۱.۹۷mg/g DCW) and squalene yield (۱۲.۰۱ ± ۱.۱۱ mg/L) were achieved after ۹۶ hours using ۰.۲۵۸ mM and ۰.۲۷۷ mM terbinafine, respectively. The Temperature was found to be a significant factor affecting squalene synthesis in both strains. An increase in temperature led to a reduction of squalene production by Saccharomyces cerevisiae and an increase by Cystobasidium benthicum. Conclusion The present study demonstrated that Saccharomyces cerevisiae and Cystobasidium benthicum are both potential sources of squalene production. Saccharomyces cerevisiae is a safe and versatile yeast that can adapt well to a controlled fermentation environment and grow quickly, making it a favorable option for commercial production. While Cystobasidium benthicum may not be as widely available, it can compete with Saccharomyces cerevisiae in terms of squalene production and is a suitable strain for this purpose.