Sato Rintaro, Tanaka Tomonari, Ohara Hitomi, Aso Yuji
Department of Biobased Materials Science, Kyoto Institute of Technology, Kyoto, Japan.
JST-Mirai Program, Japan Science and Technology Agency, Saitama, Japan.
Curr Microbiol. 2020 Nov;77(11):3704-3710. doi: 10.1007/s00284-020-02189-8. Epub 2020 Sep 9.
Diols are versatile chemicals used for multiple manufacturing products. In some previous studies, Escherichia coli has been engineered to produce 1,2-propanediol (1,2-PDO) and 1,3-propanediol (1,3-PDO) from glucose. However, there are no reports on the direct production of these diols from starch instead of glucose as a substrate. In this study, we directly produced 1,2-PDO and 1,3-PDO from starch using E. coli engineered for expressing a heterologous α-amylase, along with the expression of 1,2-PDO and 1,3-PDO synthetic genes. For this, the recombinant plasmids, pVUB3-SBA harboring amyA gene for α-amylase production, pSR5 harboring pct, pduP, and yahK genes for 1,2-PDO production, and pSR8 harboring gpd1-gpp2, dhaB123, gdrAB, and dhaT genes for 1,3-PDO production, were constructed. Subsequently, E. coli BW25113 (ΔpflA) and BW25113 strains were transformed with pVUB3-SBA, pSR5, and/or pSR8. Using these transformants, direct production of 1,2-PDO and 1,3-PDO from starch was demonstrated under microaerobic condition. As a result, the maximum production titers of 1,2-PDO and 1,3-PDO from 1% glucose as a sole carbon source were 13 mg/L and 150 mg/L, respectively. The maximum production titers from 1% starch were similar levels (30 mg/L 1,2-PDO and 120 mg/L 1,3-PDO). These data indicate that starch can be an alternative carbon source for the production of 1,2-PDO and 1,3-PDO in engineered E. coli. This technology could simplify the upstream process of diol bioproduction.
二醇是用于多种制造产品的通用化学品。在一些先前的研究中，大肠杆菌已被改造用于从葡萄糖生产1,2 - 丙二醇（1,2 - PDO）和1,3 - 丙二醇（1,3 - PDO）。然而，尚无关于以淀粉而非葡萄糖作为底物直接生产这些二醇的报道。在本研究中，我们使用经过改造以表达异源α - 淀粉酶的大肠杆菌，以及1,2 - PDO和1,3 - PDO合成基因的表达，直接从淀粉生产1,2 - PDO和1,3 - PDO。为此，构建了重组质粒，携带用于α - 淀粉酶生产的amyA基因的pVUB3 - SBA、携带用于1,2 - PDO生产的pct、pduP和yahK基因的pSR5，以及携带用于1,3 - PDO生产的gpd1 - gpp2、dhaB123、gdrAB和dhaT基因的pSR8。随后，用pVUB3 - SBA、pSR5和/或pSR8转化大肠杆菌BW25113（ΔpflA）和BW25113菌株。使用这些转化体，在微需氧条件下证明了从淀粉直接生产1,2 - PDO和1,3 - PDO。结果，以1%葡萄糖作为唯一碳源时，1,2 - PDO和1,3 - PDO的最大生产滴度分别为13 mg/L和150 mg/L。以1%淀粉为原料时的最大生产滴度为相似水平（30 mg/L 1,2 - PDO和120 mg/L 1,3 - PDO）。这些数据表明淀粉可以作为工程化大肠杆菌中生产1,2 - PDO和1,3 - PDO的替代碳源。该技术可以简化二醇生物生产的上游过程。
