Wu Na, Zhang Jiahui, Ou Wen, Chen Yaru, Wang Ru, Li Ke, Sun Xiao-Man, Li Yingfeng, Xu Qing, Huang He
School of Food Science and Pharmaceutical Engineering, Nanjing Normal University, Nanjing, China.
Biotechnol Biofuels. 2021 Dec 4;14(1):230. doi: 10.1186/s13068-021-02081-y.
Rhizopus oryzae (R. oryzae) can effectively produce organic acids, and its pellet formation in seed cultures has been shown to significantly enhance subsequent fermentation processes. Despite advances in strain development, simple and effective methods for inducing pellet morphology and a basic understanding of the mechanisms controlling this process could facilitate substantial increases in efficiency and product output. Here, we report that 1.5% triethanolamine (TEOA) in seed culture medium can activate the growth of R. oryzae spores in compact and uniform pellets which is optimal for fermentation conditions. Analysis of fermentation kinetics showed that the production of fumaric and L-malic acid increases 293% and 177%, respectively. Transcriptomic analysis revealed that exposure of R. oryzae to 1.5% TEOA during the seed culture activated the phosphatidylinositol and mitogen-activated protein kinase signaling pathways. Theses pathways subsequently stimulated the downstream carbohydrate-active synthases and hydrolases that required for cell wall component synthesis and reconstruction. Our results thus provide insight into the regulatory pathways controlling pellet morphology germane to the viability of seed cultures, and provide valuable reference data for subsequent optimization of organic acid fermentation by R. oryzae.
米根霉（R. oryzae）能够有效地产生有机酸，并且已证明其在种子培养物中形成菌球可显著增强后续的发酵过程。尽管在菌株开发方面取得了进展，但诱导菌球形态的简单有效方法以及对控制该过程机制的基本了解，有助于大幅提高效率和产品产量。在此，我们报告在种子培养基中添加1.5%的三乙醇胺（TEOA）可促使米根霉孢子生长形成紧密且均匀的菌球，这对于发酵条件而言是最优的。发酵动力学分析表明，富马酸和L-苹果酸的产量分别增加了293%和177%。转录组分析显示，在种子培养期间，米根霉暴露于1.5%的TEOA会激活磷脂酰肌醇和丝裂原活化蛋白激酶信号通路。这些信号通路随后刺激了细胞壁成分合成和重建所需的下游碳水化合物活性合成酶和水解酶。因此，我们的研究结果揭示了控制与种子培养物活力相关的菌球形态的调控途径，并为后续米根霉有机酸发酵的优化提供了有价值的参考数据。
