不同发酵条件下产甘油假丝酵母有机酸代谢的研究

产甘油假丝酵母 (Candidaglycerolgenesis)发酵产生的有机酸对丙三醇产品质量和产率均有影响。发现在发酵其它条件恒定 ,装液比和玉米浆浓度增加时 ,发酵液总酸是递增的。在装液比为 0 2和玉米浆浓度为 8g L时 ,丙酮酸和乳酸在细胞生长期可分别积累达 4 1g L和 1 0g L ,比正常发酵时增加 2倍以上 ,丙三醇产率也低 ;然而 ,装液比为 0 0 8和玉米浆浓度为 4g L时 ,丙酮酸和乳酸产生较低 ,丙三醇产率较高 ,但乙酸积累比供氧不足时高 ,可达 2 6g L。发酵过程中有机酸被细胞代谢 ,含量逐渐下降 ,如在初糖浓度为 1 0 0g L时 ,有机酸在细胞生长期积累至高峰后 ,丙三醇和有机酸随之均降低至较低含量 ,并且丙酮酸或乳酸可以转化为乙酸。此外 ,在外加一些添加剂时对其产生有机酸也有影响 ,如添加 1 %油酸和VB1时可以降低乙酸的积累 ,同时增加丙酮酸的含量 ,丙三醇产量也有所增加 ;而丙酮酸结构类似物氟代丙酮酸和亚硫酸盐促进乙酸的产生 ,使酮戊二酸合成减少 ,丙三醇产量约增加 2 0 %。

STUDY ON THE ORGANIC ACIDS METABOLISM IN CANDIDA GLYCERO- LGENESIS UNDER DIFFERENT FERMENTATION CONDITIONS

The organic acids in Candida glycerolgenesis fermentation medium affected both the glycerol yield and quality. When other fermentation condition was constant, the total acidity in medium increased when the volumetric ratio of medium to flask and corn steep liquid concentration were increased. When the volumetric ratio of medium to flask was 0.20 and the corn steep liqud concentration was 8g/L, there have high yield of pyruvate and lactate produced at growth phase, 4.1g/L and 1.0g/L, respectively, which are two times than control sample at usual fermentation condition, hence, the glycerol yield was lower. However, the volumetric ratio of medium to flask was 0.08 and the corn steep liquid concentration was 4g/L, the yield of pyruvate and lactate were lower and the glycerol yield was higher, but the acetate could be accumulated to 2.6g/L.The organic acids also could be metabolized in final fermentation process, such as the initial glucose concentration was 100g/L, after the glucose was completely uitilized, both the glycerol and organic acids concentration decreased, and pyruvate or lactate could be converted to acetate in following fermentation process. In addition, the additive also can change the production of organic acids, with the addition of 1% oleic acid or V B1 the acetate concentration could be decreased and increased the production of pyruvate, hence, improve the yield of glycerol. While the fluoro-pyruvate or sulphite were added in medium, the acetate was increased largely and ketoglutarate was decreased accordingly, also increase the glycerol yields about 20%.