金色链霉菌碳代谢流量变化特性的研究

Study on Carbon Metabolic Flux Characteristic of Streptomyces aureofaciens

建立简化的金色链霉菌代谢网络模型,根据其在复合培养基上的代谢特性,用优化手段求解细胞内碳代谢网络流量。根据不同时期金色链霉菌细胞内碳代谢流的分布,分析金色链霉菌生长代谢过程的碳代谢特性。研究表明, 在对数生长期,碳在EMP途径的通量为0.701mmolg-1h-1,占66.6%,进入HMS途径的流量为0.353mmolg-1h-1,占总碳消耗量的33.4%;在产物合成期,进入EMP途径的代谢流量降至0.382mmolg-1h-1,占进入细胞总碳流量的的51.6%;进入HMS途径的碳为0.358mmolg-1h-1,占48.4%。磷酸己糖旁路HMS通量对金霉素的合成起重要的调节作用, 添加磷酸盐和芳香性氨基酸抑制HMS途径的碳代谢通量,金霉素合成量分别降低50%以上。

A simplified carbon metabolic network of streptomyces aureofaciens cultured in complex medium was established and according to the specific rates of cell growth, carbon consumption and metabolites formation, the metabolic flux distribution in the network was estimated by an optimized method Analysis of metabolic flux distribution in different fermentation phase was favorable to understanding the fermentation characteristics of the process. During the exponential phase (17 h), the carbon flux distributed in EMP was 0.701mmolg-1h-1, and occupied 66.6% of total carbon assumed by the cells; it was 0.353 mmolg-1h-1 through Hexose Monophosphate Shunt (HMS), and occupied about 33.4%. During the antibiotic-production phase, 51.6% carbon distributed in EMP, and the flux was 0.382mmolg-1h-1; the flux through HMS was 0.358mmolg-1h-1, and occupied 48.4%. The carbon flux through HMS regulated the biosynthesis of chlortetracycline to a great extent, and inhibition of carbon flow in HMS by adding 0.5gL-1 phosphate or 0.1gL-1 aromatic acids had negative effect on biosynthesis of chlortetracycline and CTC yield reduced more than 50%.