Ikushima Shigehito, Fujii Toshio, Kobayashi Osamu, Yoshida Satoshi, Yoshida Aruto
Central Laboratories for Frontier Technology, KIRIN Holdings Co., Ltd., Yokohama, Kanagawa, Japan.
Biosci Biotechnol Biochem. 2009 Aug;73(8):1818-24. doi: 10.1271/bbb.90186. Epub 2009 Aug 7.
Polylactic acid is receiving increasing attention as a renewable alternative for conventional petroleum-based plastics. In the present study, we constructed a metabolically-engineered Candida utilis strain that produces L-lactic acid with the highest efficiency yet reported in yeasts. Initially, the gene encoding pyruvate decarboxylase (CuPDC1) was identified, followed by four CuPDC1 disruption events in order to obtain a null mutant that produced little ethanol (a by-product of L-lactic acid). Two copies of the L-lactate dehydrogenase (L-LDH) gene derived from Bos taurus under the control of the CuPDC1 promoter were then integrated into the genome of the CuPdc1-null deletant. The resulting strain produced 103.3 g/l of L-lactic acid from 108.7 g/l of glucose in 33 h, representing a 95.1% conversion. The maximum production rate of L-lactic acid was 4.9 g/l/h. The optical purity of the L-lactic acid was found to be more than 99.9% e.e.
聚乳酸作为一种可再生的传统石油基塑料替代品，正受到越来越多的关注。在本研究中，我们构建了一种代谢工程改造的产朊假丝酵母菌株，该菌株能以酵母中迄今报道的最高效率生产L-乳酸。首先，鉴定了编码丙酮酸脱羧酶的基因（CuPDC1），随后进行了四次CuPDC1破坏事件，以获得几乎不产生乙醇（L-乳酸的副产物）的无效突变体。然后，将两个在CuPDC1启动子控制下的源自牛的L-乳酸脱氢酶（L-LDH）基因拷贝整合到CuPdc1无效缺失体的基因组中。所得菌株在33小时内从108.7 g/l葡萄糖中产生了103.3 g/l的L-乳酸，转化率为95.1%。L-乳酸的最大生产率为4.9 g/l/h。发现L-乳酸的光学纯度超过99.9% e.e.
