College of Food Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China; Institute of Agro-Product Processing, Jiangsu Academy of Agricultural Sciences, Nanjing, Jiangsu 210095, China.
Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
Bioresour Technol. 2016 Oct;218:999-1007. doi: 10.1016/j.biortech.2016.07.066. Epub 2016 Jul 18.
Microbial fermentations promise to revolutionize the conventional extraction of (2S)-pinocembrin from natural plant sources. Previously an Escherichia coli fermentation system was developed for one-step (2S)-pinocembrin production. However, this fermentation platform need supplementation of expensive malonyl-CoA precursor malonate and requires morpholinopropane sulfonate to provide buffering capacity. Here, a clustered regularly interspaced short palindromic repeats interference was constructed to efficiently channel carbon flux toward malonyl-CoA. By exploring the effects of different culture pH on microbial fermentation, it was found that high pH values favored upstream pathway catalysis, while low pH values favored downstream pathway catalysis. Based on this theory, a two-stage pH control strategy was proposed. The pH was controlled at 7.0 during 0-10h, and was shifted to 6.5 after 10h. Finally, the (2S)-pinocembrin titers increased to 525.8mg/L. These results were attained in minimal medium without additional precursor supplementation, thus offering opportunities for industrial scale low-cost production of flavonoids.
微生物发酵有望彻底改变从天然植物资源中常规提取（2S）-松属素的方式。先前，已经开发出一种用于一步法（2S）-松属素生产的大肠杆菌发酵系统。然而，这种发酵平台需要补充昂贵的丙二酰辅酶 A 前体丙二酸盐，并需要吗啉丙烷磺酸提供缓冲能力。在这里，构建了成簇规律间隔短回文重复干扰，以有效地将碳通量导向丙二酰辅酶 A。通过探索不同培养 pH 值对微生物发酵的影响，发现高 pH 值有利于上游途径的催化，而低 pH 值有利于下游途径的催化。基于这一理论，提出了一种两阶段 pH 值控制策略。在 0-10 小时内将 pH 值控制在 7.0，10 小时后将 pH 值调整为 6.5。最终，（2S）-松属素的浓度提高到 525.8mg/L。这些结果是在没有额外前体补充的基础培养基中获得的，因此为黄酮类化合物的工业规模低成本生产提供了机会。
