代谢通量分析优化米根霉R1021发酵生产L(+)-乳酸过程

Optimization of L(+)Lactic Acid Fermentation by Rhizopus oryzae R1021 by Metabolic Flux Analysis

建立了米根霉R1021的代谢网络,分析了米根霉R1021在分批发酵过程中不同阶段、不同氮源浓度、不同供氧量条件下的代谢通量分布,确定PYR是米根霉代谢网络上的关键节点,此节点的通量分配比影响着乳酸的最终产率.在米根霉发酵中,当NH4NO3质量浓度为2.0g/L,空气体积流量为2L/min时,流向乳酸的代谢流最大.通过对模型进行优化计算得到L(+) 乳酸的最大理论得率YP/S为98.2%.

A detailed flux analysis of glucose metabolism for L(+)lactic acid production by filamentous fungus Rhizopus oryzae R1021 was carried out. On the basis of metabolic mechanism of Rhizopus oryzae, a complete metabolic network of Rhizopus oryzae was constructed, including glycolytic pathway, tricarboxylic acid cycle and the pathways to synthesize various kinds of precursors such as animo acids and nucleic acids. The uptake and production rates of glucose, biomass, L(+)lactate, malate, fumarate, ethanol, O2 and CO2 were measured, and fluxes through the metabolic network of Rhizopus oryzae were estimated by using these known experiment data. Based on the flux analysis of this system, the metabolic flux distributions were shown for different conditions. The results showed that the optimal NH4NO3 concentration and aeration rate were 2 g/L and 2 L/min, respectively. The theoretic yield of L(+)lactic acid was 98.2% by model optimization calculation.