Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China.
University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
Microb Cell Fact. 2018 Jun 25;17(1):99. doi: 10.1186/s12934-018-0946-3.
Global energy and resource shortages make it necessary to quest for renewable resources. n-Caproic acid (CA) production based on carboxylate platform by anaerobic fermentation is booming. Recently, a novel Ruminococcaceae bacterium CPB6 is shown to be a potential biotransformation factory for CA production from lactate-containing wastewater. However, little is known about the effects of different electron acceptors (EAs) on the fermentative products of strain CPB6, as well as the optimum medium for CA production.
In this study, batch experiments were performed to investigate the fermentative products of strain CPB6 in a lactate medium supplemented with different EAs and sugars. Supplementation of acetate, butyrate and sucrose dramatically increased cell growth and CA production. The addition of propionate or pentanoate resulted in the production of C5 or C7 carboxylic acid, respectively. Further, a Box-Behnken experiment was conducted to optimize the culture medium for CA production. The result indicated that a medium containing 13.30 g/L sucrose, 22.35 g/L lactate and 16.48 g/L butyrate supported high-titer CA production (16.73 g/L) with a maximum productivity of 6.50 g/L/day.
This study demonstrated that strain CPB6 could produce C6-C7 carboxylic acids from lactate (as electron donor) with C2-C5 short-chain carboxylic acids (as EAs), but CA (C6 carboxylic acid) was the most major and potential product. Butyrate and sucrose were the most significant EA and carbon source respectively for CA production from lactate by strain CPB6. High titer of CA can be produced from a synthetic substrate containing sucrose, lactate and butyrate. The work provided significant implications for improving CA production in industry-scale.
全球能源和资源短缺使得人们有必要寻求可再生资源。基于羧酸平台的厌氧发酵生产正辛酸（CA）方兴未艾。最近，一种新型的瘤胃球菌科细菌 CPB6 被证明是一种从含乳酸废水生产 CA 的潜在生物转化工厂。然而，人们对不同电子受体（EA）对 CPB6 菌株发酵产物的影响以及 CA 生产的最佳培养基知之甚少。
本研究通过批式实验，研究了 CPB6 菌株在添加不同 EA 和糖的乳酸培养基中的发酵产物。添加乙酸盐、丁酸盐和蔗糖可显著促进细胞生长和 CA 生产。丙酸或戊酸盐的添加分别导致 C5 或 C7 羧酸的产生。进一步，采用 Box-Behnken 实验对 CA 生产的培养基进行了优化。结果表明，含有 13.30 g/L 蔗糖、22.35 g/L 乳酸和 16.48 g/L 丁酸盐的培养基支持 CA 高产（16.73 g/L），最大产率为 6.50 g/L/天。
本研究表明 CPB6 菌株可以从乳酸（作为电子供体）与 C2-C5 短链羧酸（作为 EA）生产 C6-C7 羧酸，但 CA（C6 羧酸）是最主要和潜在的产物。丁酸盐和蔗糖分别是 CPB6 菌株从乳酸生产 CA 的最显著 EA 和碳源。高浓度 CA 可从含有蔗糖、乳酸和丁酸盐的合成基质中产生。这项工作为提高工业规模 CA 生产提供了重要启示。
