Hannya Asuka, Nishimura Taku, Matsushita Isao, Tsubota Jun, Kawata Yoshikazu
Energy Technology Laboratories, OSAKA GAS Co., Ltd., 6-19-9 Torishima, Konohana-ku, Osaka, 554-0051, Japan.
Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka, 563-8577, Japan.
AMB Express. 2017 Nov 21;7(1):209. doi: 10.1186/s13568-017-0516-9.
The alkaliphilic, halophilic bacterium Halomonas sp. KM-1 can utilize glucose for the intracellular storage of the bioplastic poly-(R)-3-hydroxybutyric acid (PHB) and extracellular secretion of pyruvate under aerobic conditions. In this study, we investigated the effects of sodium chloride concentration on PHB accumulation and pyruvate secretion in the KM-1 strain and, unexpectedly, observed that oxaloacetate, an important intermediate chemical in the TCA cycle, glycogenesis, and aspartic acid biosynthesis, was secreted. We then further analyzed oxaloacetate productivity after changing the sodium chloride additive concentration, additive time-shift, and culture temperature. In 42-h batch-cultivation experiments, we found that wild-type Halomonas sp. KM-1 secreted 39.0 g/L oxaloacetate at a rate of 0.93 g/(L h). The halophilic bacteria Halomonas has already gained attention for industrial chemical-production processes owing to its unique properties, such as contamination-free culture conditions and a tolerance for high substrate concentrations. Moreover, no commercial scale oxaloacetate production was previously reported to result from bacterial fermentation. Oxaloacetate is an important intermediate chemical in biosynthesis and is used as a health food based on its role in energy synthesis. Thus, these data provided important insights into the production of oxaloacetate and other derivative chemicals using this strain.
嗜碱嗜盐细菌盐单胞菌属KM-1能够在有氧条件下利用葡萄糖进行生物塑料聚（R）-3-羟基丁酸（PHB）的细胞内储存以及丙酮酸的细胞外分泌。在本研究中，我们调查了氯化钠浓度对KM-1菌株中PHB积累和丙酮酸分泌的影响，并且意外地观察到三羧酸循环、糖原生成和天冬氨酸生物合成中的重要中间化学物质草酰乙酸被分泌出来。然后，我们在改变氯化钠添加浓度、添加时间和培养温度后进一步分析了草酰乙酸的生产率。在42小时的分批培养实验中，我们发现野生型盐单胞菌属KM-1以0.93克/（升·小时）的速率分泌了39.0克/升的草酰乙酸。嗜盐细菌盐单胞菌属因其独特的特性，如无污染的培养条件和对高底物浓度的耐受性，已在工业化学品生产过程中受到关注。此外，以前没有报道过通过细菌发酵进行商业规模的草酰乙酸生产。草酰乙酸是生物合成中的一种重要中间化学物质，并因其在能量合成中的作用而被用作保健食品。因此，这些数据为利用该菌株生产草酰乙酸和其他衍生化学品提供了重要的见解。
