ANTIOXIDANT ROLE OF CAROTENOIDS IN PHAFFIA-RHODOZYMA

The role of carotenoids in protecting the yeast Phaffia rhodozyma against reactive oxygen species was studied. Addition of the O2--generator duroquinone (DQ) to yeast-malt broth increased total carotenoid content as well as the relative amounts of xanthophylls present, while the reactive oxygen scavenger mannitol reversed this effect. Resistance to DQ increased in the stationary phase, particularly in the carotenoid-hyperproducing strain studied. Assay of superoxide dismutase (SOD) in P. rhodozyma indicated the presence of Mn-SOD and the complete absence of Fe-SOD and Cu/Zn-SOD. Catalase activity in P. rhodozyma was significantly lower than in Saccharomyces cerevisiae, particularly in stationary cultures. In young cells, H2O2 resistance was directly related to carotenoid levels, and selection of cultures based on peroxide resistance resulted in slightly increased carotenoid production. These results indicate that carotenoids play an antioxidant role during ageing in P. rhodozyma.