两阶段pH控制方式提高富硒产朊假丝酵母的性能

Improved Performance of Selenium-Enriched Candida utilis Using a Two-stage pH Control Strategy

为了提高富硒产朊假丝酵母的性能,本文在摇瓶培养和分批培养的基础上,考察了不同pH控制方式对流加培养条件下富硒产朊假丝酵母细胞生长、谷胱甘肽(GSH)合成和有机硒转化的影响,结果发现:在12 h将pH从3.5切换至5.5(pH 3.5→5.5)的两阶段pH控制方式最有利于富硒产朊假丝酵母胞内GSH和有机硒含量的提高。在pH3.5→5.5条件下,富硒产朊假丝酵母胞内GSH含量、有机硒含量和有机硒转化率分别达到最大值13.09mg/g、1.88mg/g和94.69%。通过对酵母胞内GSH合成关键酶活性、氧化还原酶活性和能量代谢物质ATP水平进行测定,发现pH 3.5→5.5两阶段pH控制方式提高了富硒酵母胞内过氧化氢酶活性,降低了丙二醛含量,为酵母进行有机硒富集与转化以及GSH合成与积累提供了合适的氧化还原环境,并最终提高了富硒酵母的性能。

Effects of different pH control modes on yeast cell growth,glutathione biosynthesis and organic selenium(Se)transformation during fed-batch culture of Se-enriched Candida utilis were investigated.Based on the results derived from both flask culture and batch culture,the fed-batch culture was carried out to improve the performance of Se-enriched C.utilis.A two-stage pH control strategy of shifting pH from 3.5 to 5.5 at 12 h(pH 3.5→5.5)was found to be the optimum condition for the increase in intracellular GSH and organic Se contents of Se-enriched C.utilis.The maximal intracellular glutathione,organic selenium content and organic selenium bioconversion rate of 13.09 mg/g,1.88 mg/g and 94.69%were achieved,respectively,under pH 3.5→5.5.According to the assay of key enzyme activity involved in glutathione biosynthesis,the measurement of intracellular oxidoreductases,and the determination of energy metabolism substance ATP,the two-stage pH control strategy of pH 3.5→5.5 was found to favor the increase in catalase activity and the decrease in malondialdehyde content of Se-enriched C.utilis.Results indicated that pH 3.5→5.5 provided appropriate intracellular redox environment for selenium assimilation and transformation,as well as glutathione biosynthesis and accumulation,all of which ultimately improved the performance of Se-enriched yeast.