磷酸盐对Escherichia coli TRJHL-色氨酸发酵代谢流分布的影响

应用代谢流分析方法研究了磷酸盐对Escheriehia coli TRJHL-色氨酸发酵中后期胞内代谢流分布的影响．结果表明：在发酵中后期添加4．0g／LKH2P04时，与不添加KH2P04相比，L-色氨酸合成的代谢流增加了19．3％，而副产物Lac、HAc和Ala的代谢流仅增加了6．0％、7．8％和6．8％．与添加8．0g／LKH2P04比较，副产物代谢流的增量明显减少，说明磷酸盐的过量添加会使EMP途径代谢流量超过TCA及L-色氨酸合成支路的代谢能力，从而导致副产物的生成增加，L-色氨酸生物合成的转化率相对降低．因此，在L-色氨酸发酵过程中应该严格控制磷酸盐的用量．

Effects of Phosphate on Metabolic Flux Distributions of L-tryptophan Production by Escherichia coli TRJH

In order to study the effects of phosphate on the metabolic flux distributions in Escherichia coli TRJH fermentation during the middle and late period,the metabolic flux analysis of the L-tryptophan biosynthesis at pseudo steady state was conducted. The results show that the metabolic flux with 4.0 g/L addition of KH2PO4 channeled to the L-tryptophan synthesis pathway increased by 19.3% compared to that without KH2PO4,while the metabolic flux of by-product including Lae,HAc and Ala increased by only 6.0%, 7.8% and 6.8%. The incremental metabolic flux of by-product decreased significantly compared to 8.0 g/L addition of KH2PO4. The excess of phosphate made the metabolic flux channeled to EMP pathway exceed the requirements of TCA Cycle and L-tryptophan biosynthesis,which leading to the increasing of by-products and relatively decreasing of L-tryptophan biosynthesis rate. Therefore,the amount of phosphate should be strictly controlled in the L- tryptophan fermentation process.