Improving carotenoid production in recombinant yeast, Saccharomyces cerevisiae, using ultrasound‐irradiated two‐phase extractive fermentation

Carotenoids are hydrophobic compounds that exhibit excellent bioactivity and can be produced by recombinant S. cerevisiae. Irradiating microorganisms with ultrasonic waves increase the productivity of various useful chemicals. Ultrasonic waves are also used to extract useful chemicals that accumulate in microbial cells. In this study, we aimed to improve the carotenoid production efficiency of a recombinant S. cerevisiae using an ultrasonic‐irradiation based two‐phase extractive fermentation process. When isopropyl myristate was used as the extraction solvent, a total of 264 mg/L of carotenoid was produced when batches were subjected to ultrasonic‐irradiation at 10 W, which was a 1.3‐fold increase when compared to the control. Transcriptome analysis suggested that one of the reasons for this improvement was an increase in the number of living cells. In fact, after 96 h of fermentation, the number of living cells increased by 1.4‐fold upon irradiation with ultrasonic waves. Consequently, we succeeded in improving the carotenoid production in a recombinant S. cerevisiae strain using a ultrasonic‐irradiated two‐phase extractive fermentation and isopropyl myristate as the solvent. This fermentation strategy has the potential to be widely applied during the production of hydrophobic chemicals in recombinant yeast, and future research is expected to further develop this process.