红酵母的抗氧化机制与高产类胡萝卜素菌株的筛选*

通过聚丙烯酰胺凝胶电泳(PAGE)和超氧化物歧化酶(SOD)的鉴别性定位染色分析,表明红酵母Rhodotorula sp.仅存在线粒体中的Mn-SOD。在类胡萝卜素含量较高的时期(培养5d),红酵母SOD活力下降, 过氧化氢酶(CAT)活力升高,而此时它对外界O2-. 和H2O2的抗性均明显高于类胡萝卜素含量较低的时期(培养2d)。以上结果表明红酵母胞质中的抗氧化作用已主要由类胡萝卜素来承担,类胡萝卜素含量越高,红酵母抗氧化能力越强。由此,利用产生的O2-. 试剂TBO处理红酵母,可筛选出稳定高产的类胡萝卜素菌株,其中以培养2d的红酵母作为筛选对象更佳,所筛菌落类胡萝卜素含量可高达1740.9~2039.2g/g干重,比未处理的对照增加了28.2%~50.1%。

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).