Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea.
Cell Factory Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Republic of Korea.
Biotechnol Bioeng. 2018 Sep;115(9):2232-2242. doi: 10.1002/bit.26745. Epub 2018 Jul 6.
Lactic acid is a platform chemical for the sustainable production of various materials. To develop a robust yeast platform for low-pH production of d-lactic acid (LA), an acid-tolerant yeast strain was isolated from grape skins and named Pichia kudriavzevii NG7 by ribosomal RNA sequencing. This strain could grow at pH 2.0 and 50°C. For the commercial application of P. kudriavzevii NG7 as a lactic acid producer, the ethanol fermentation pathway was redirected to lactic acid by replacing the pyruvate decarboxylase 1 gene (PDC1) with the d-lactate dehydrogenase gene (d-LDH) derived from Lactobacillus plantarum. To enhance lactic acid tolerance, this engineered strain was adapted to high lactic acid concentrations, and a new transcriptional regulator, PAR1, responsible for acid tolerance, was identified by whole-genome resequencing. The final engineered strain produced 135 g/L and 154 g/L of d-LA with productivity over 3.66 g/L/hr at pH 3.6 and 4.16 g/L/hr at pH 4.7, respectively.
乳酸是一种用于可持续生产各种材料的平台化学品。为了开发用于在低 pH 值下生产 d-乳酸 (LA) 的稳健酵母平台，我们通过核糖体 RNA 测序从葡萄皮中分离出一种耐酸酵母菌株，并将其命名为 Pichia kudriavzevii NG7。该菌株可以在 pH 值为 2.0 和 50°C 的条件下生长。为了将 P. kudriavzevii NG7 作为乳酸生产菌商业化应用，我们通过用来自植物乳杆菌的 d-乳酸脱氢酶基因 (d-LDH) 替换丙酮酸脱羧酶 1 基因 (PDC1)，将乙醇发酵途径重新定向为乳酸。为了提高乳酸耐受性，我们对该工程菌株进行了高浓度乳酸的适应性进化，并通过全基因组重测序鉴定了一种新的转录调节因子 PAR1，它负责菌株的耐酸能力。最终的工程菌株在 pH 值为 3.6 和 4.16 时分别产生了 135 g/L 和 154 g/L 的 d-LA，产率分别超过 3.66 g/L/hr 和 4.16 g/L/hr。
