To identify beneficial oxygen vectors for Phaffia rhodozyma in liquid cultures, and to evaluate their use to improve the oxygen transfer and carotenoid production in the yeast cultures. Several liquid hydrocarbons were tested as oxygen vectors for improving the yeast growth and carotenoid production in shake-flask cultures of P. rhodozyma. While all nontoxic organic liquids (Log P: > or =5.6) showed a positive effect, n-hexadecane was proved to be the most beneficial for the yeast growth and carotenoid production. The addition of 9% (v/v) n-hexadecane to the liquid medium at the time of inoculation was found to be optimal, increasing the carotenoid yield by 58% (14.5 mg l(-1) vs 9.2 g l(-1) in the control) and the oxygen transfer rate (OTR) by 90%. The addition of n-hexadecane to shake-flask cultures of P. rhodozyma significantly improved the oxygen transfer in culture, thus increasing the carotenoid production. Use of organic oxygen vectors such as n-hexadecane may be a simple and useful means for enhancing oxygen transfer and carotenoid production in liquid fermentation of P. rhodozyma.
