乳酸钠促进法夫酵母虾青素合成代谢流作用分析

Metabolic flux regulation of sodium lactate on astaxanthin synthesis during Phaffia rhodozyma fermentation

【目的】研究乳酸钠(一种糖代谢产物)的加入对法夫酵母JMU-VDL668发酵过程中细胞生长和虾青素合成的影响。【方法】分别在摇瓶和7 L发酵罐实验基础上,采用代谢通量分析的方法分析添加乳酸钠对法夫酵母菌株JMU-VDL668合成虾青素代谢流的影响。【结果】在7 L发酵罐实验中添加乳酸钠,虾青素产量最高可达17.70 mg/L,与对照组相比提高26%。代谢通量分析表明,乳酸钠可以调节丙酮酸、乙酰辅酶A节点处的代谢通量分布,乳酸在乳酸脱氢酶的作用下可以直接进入代谢网络的后半程,乙酰辅酶A的通量和进入TCA循环的通量得到了显著加强。【结论】乳酸钠的加入提供了更多的乙酰辅酶A等前体物质和能量供给,因此促进了虾青素的合成。

[Objective] To interpret the effect of sodium lactate（a carbohydrate metabolite） on cell growth and astaxanthin accumlation during Phaffia rhodozyma fermentation, based on the metabolic regulation mechanism of astaxanthin synthesis. [Methods] The astaxanthin producing strain Phaffia rhodozyma JMU-VDL668 was cultured in shake flasks and 7 L bioreactor respectively. The effect of sodium lactate on the synthetic metabolic flow of astaxanthin was studied with the method of metabolic flux analysis. [Results] It was found that adding sodium lactate into 7 L bioreactor increased astaxanthin accumulation significantly, and the production of astaxanthin reached 17.70 mg/L, which was 26% higher than the production of the control group. The regulation mechanism of sodium lactate on astaxanthin synthesis was studied by means of metabolic flux analysis, and it was shown that sodium lactate could adjust metabolic flux distribution at the nodes of pyruvate and acetyl-Co A. Lactate was catalyzed by dehydrogenase and directly into later half of the metabolic network. Thus the flux of acetyl-Co A and the flux down to TCA cycle were significantly increased. [Conclusion] Adding sodium lactate during fermentation could provide more precursors（acetyl-Co A etc.） and energy, and so improved astaxanthin synthesis.