米曲霉FMME-S-38基因组规模代谢网络模型重构与解析

Reconstruction and Analysis of Genome-scale Metabolic Model of Aspergillus oryzae FMME-S-38

摘要:

【目的】 构建并解析L-苹果酸高产菌株米曲霉（Aspergillus oryzae， A. oryzae）FMME-S-38的基因组规模代谢网络模型（GSMM）。 【方法】 通过粗模型构建和模型精细优化2个步骤，构建L-苹果酸高产菌株米曲霉FMME-S-38的GSMM，命名为iJW1333。 【结果】 该模型系统整合了1 723个生化反应、1 723个代谢物以及1 333个功能基因，对底物代谢和菌体生长模拟的预测准确度分别为94.6%和92.0%。通过比较基因组，发现还原磷酸戊糖途径（HMP）和氧化磷酸化基因突变是导致米曲霉FMME-S-38高产L-苹果酸的生理原因。氮源与辅因子（NADH和ATP）是影响L-苹果酸高效合成的关键因素，通过降低氮源质量浓度和溶氧（DO）水平，能弱化HMP并强化还原性三羧酸循环（rTCA）分支，使米曲霉FMME-S-38发酵生产L-苹果酸的产量达到（154.2±1.8） g/L。 【结论】 该研究有利于确定米曲霉FMME-S-38高产L-苹果酸关键路径和生理机制，为利用其生产其他有价值代谢产物奠定基础。

Abstract:

[Objective] A genome-scale metabolic model (GSMM) of the high L-malic acid-producing strain Aspergillus oryzae (A. oryzae) FMME-S-38 was constructed and analyzed. [Method] The new GSMM iJW1333 was established for A. oryzae FMME-S-38 through a two-step process of draft reconstruction and model refinement. [Result] The model integrated 1 723 biochemical reactions, 1 723 metabolites, and 1 333 functional genes, achieving the prediction accuracy of 94.6% for substrate metabolism and 92.0% for cell growth. Comparative genomic analysis revealed that mutations in the genes involved in the hexose monophosphate pathway (HMP) and oxidative phosphorylation underpinned the enhanced L-malic acid production of A. oryzae FMME-S-38. Nitrogen source and cofactors (NADH and ATP) were identified as key determinants of efficient L-malic acid biosynthesis. Reducing the mass concentration of nitrogen source and the level of dissolved oxygen (DO) attenuated HMP while strengthening the reductive tricarboxylic acid (rTCA) branch, enabling A. oryzae FMME-S-38 to achieve an L-malic acid titer of (154.2±1.8) g/L.[Conclusion] This study clarifies the critical pathways and physiological mechanisms responsible for high L-malic acid production, providing a solid foundation for employing A. oryzae FMME-S-38 in the biosynthesis of other valuable metabolites.