ANTIOXIDANT ROLE OF CAROTENOIDS IN RHODOTORULA SP. AND A PROTOCAL FOR SCREENING CAROTENOID HYPERPRODUCING YEASTS

The isoenzyme types of superoxide dismutase (SOD) in Rhodotorula sp. were assayed with activity staining of electrophoresis gels and it indicated the presence of Mn-SOD and the complete absence of Fe-SOD and Cu/Zn-SOD. In Rhodotorula sp., the CAT activity and H2O2 resistance all increased during transition to stationary phase (5d), the period when carotenoid production is at its highest. However, the SOD activity and O2-. resistance showed different change in this period, the former decreased and the latter increased. These results indicate that carotenoids play an antioxidant role in cytoplasm of Rhodotorula sp.. The more carotenoids it contains the higher ability as antioxidant it has. Therefore, Rhodotorula sp. was treated with Toluidine blue (TBO), which can generate O2-. on the surface of cell, to screen carotenoid- hyerproducing strains. We found that treating with 2-d-old cultures was more efficient. The carotenoid content of 2d old cultures treated with 1mmol/L TBO could reach 1740.9 ~2039.2g/g ,which was 28.2%~50.1% higher than untreated cultures (control).