초록
<P>The <SUP>13</SUP>C isotope tracer method was used to investigate the glucose metabolic flux distribution and regulation in <I>Lactobacillus amylophilus</I> to improve lactic acid production using kitchen waste saccharified solution (KWSS)<I>.</I> The results demonstrate that <I>L. amylophilus</I> is a homofermentative bacterium. In synthetic medium, 60.6% of the glucose entered the Embden–Meyerhof–Parnas (EMP) to produce lactic acid, whereas 36.4% of the glucose entered the pentose phosphate metabolic pathway (HMP). After solid–liquid separation of the KWSS, the addition of Fe<SUP>3+</SUP> during fermentation enhanced the NADPH production efficiency and increased the NADH content. The flux to the EMP was also effectively increased. Compared with the control (60.6% flux to EMP without Fe<SUP>3+</SUP> addition), the flux to the EMP with the addition of Fe<SUP>3+</SUP> (74.3%) increased by 23.8%. In the subsequent pyruvate metabolism, Fe<SUP>3+</SUP> also increased lactate dehydrogenase activity, and inhibited alcohol dehydrogenase, pyruvate dehydrogenase and pyruvate carboxylase, thereby increasing the lactic acid production to 9.03 g l<SUP>−1</SUP>, an increase of 8% compared with the control. All other organic acid by-products were lower than in the control. However, the addition of Zn<SUP>2+</SUP> showed an opposite effect, decreasing the lactic acid production. In conclusion it is feasible and effective means using GC-MS, isotope experiment and MATLAB software to integrate research the metabolic flux distribution of lactic acid bacteria, and the results provide the theoretical foundation for similar metabolic flux distribution.</P>