摘要
L 苹果酸 (LMA)高产突变株曲霉N1 1 4′在高产酸状态下 ,其胞质中催化CO2 固定反应的酶有四种 :丙酮酸羧化酶 (PC)、磷酸烯醇丙酮酸羧化酶 (PEPC)、磷酸烯醇丙酮酸羧化激酶 (PCK)和苹果酸酶 (ME) ;除ME之外 ,三种羧化酶的活性与LMA产生速率呈较好的线性正相关关系 ;苹果酸脱氢酶 (MDH)活性比PC等酶高 2～ 3个数量级 ;琥珀酸脱氢酶 (SDH)活力则明显低 ,几种酶中只有SDH与发酵醪中LMA含量呈线性正相关 (r =0 92 52 )。动态研究发现在菌丝生物量正常增长情况下 ,胞质中蛋白含量明显变化 ,通气条件的改变是引起这种变化的重要原因。各种酶活性变化与胞质蛋白量变化之间的线性相关系数呈规律性变化 :PC(r =0 9563)、PEPC (r =0 7688)、PCK (r =0 730 0 )、MDH (r =0 392 0 )、SDH (r =- 0 2 0 86)。不增加氮源 ,适当加大孢子接种量可提高LMA产率、降低琥珀酸 (SA)含量 ,提示发酵早期胞质酶合成中存在PC先于SDH这种规律的可能性。在 5L罐上通气培养 1 2 0h ,LMA含量达 1 0 5 88g/L ,平均产生速率 0 883g/(L·h) ,酸对糖转化率 78 43%。
The cytosol enzymatic study in the case of high L malic acid(LMA) production of Aspergillus sp. N1 14′ was reported. The activities of 4 kind enzymes that catalyse the CO 2 fixation reactions have been detected, which are pyruvate carboxylase(PC),phosphoenolpyruvate carboxlase(PEPC), phosphoenolpyurvate carboxykinase(PCK)and malic enzyme(ME).With the exception of ME,the linear correlation was found between activities of three carboxlases and the production rate of LMA. The activity of malate dehydrogenase(MDH)was at the level of 2～3 exponential higher than that of the other analysed enzymes, while the activity of succinate dehydrogenase(SDH)was much lower, and as a discrepancy, SDH was in a positive correlation to the content of LMA in fermenting slurry(r=0.9252).It is shown that the accumulated LMA acted as an activator of SDH. Through dynamic study, it is found that, in contrast with the slow and even increase of biomass, the content of cytosol protein(C P) sharply fluctuated mainly due to the changes of aeration conditions. The data of the linear correlation coefficients(r) of activities of cytosol enzymes to C P(PC r=0.9563,PEPC r=0.7688,PCK r=0.7300,MDH r=0.3920,SDH r=-0.2086)exhibited an inner law of protein synthesis. Experiment of increasing the amount of spore inoculum resulted in increase of LMA and decrease of SA. After fermenting 120?h in a 5?L stirred fermentor, with 3 fold of original spore inoculum 105 88?g/L of LMA was achieved, the overall productivity was 0.883?g/(L·h), the converting rate of glucose to LMA was 78.43%.This result supports the exist of a inner law of protein synthesis in the early period of LMA fermentation by Aspergillus sp. N1 14′.
出处
《微生物学报》
CAS
CSCD
北大核心
2000年第5期500-506,共7页
Acta Microbiologica Sinica
基金
广东省自然科学基金资助项目!(GDSF92 0 3 2 9)&&
关键词
L-苹果酸
直接发酵法
曲霉N1-14'
胞质酶分析
L malic acid, LMA production from carbohydrate, Aspergillus sp. N1 14′, Analysis of Cytosolic enzymes
