Leuconostoc citreum is a heterofermentative lactic acid bacterium frequently found in the various fermented foods. L. citreum EFEL2700 isolated from Korean kimchi has been used as a host strain for biotechnological applications. For the use as a food-grade host to over-produce food ingredients or enzymes, strong endogenous promoters guarantying high expression levels of target genes are necessary. In this study, transcriptomic analysis of L. citreum EFEL2700 was performed using RNA-Seq and three promoters of the most highly expressed genes were selected: glyceraldehyde 3-phosphate dehydrogenase (G3PD), 6-phosphogluconate dehydrogenase (6PGD), and phosphoketolase (PPK). Thereafter, they were used as promoters to express β-galactosidase gene from Lactobacillus plantarum WCFS1 in L. citreum EFEL2700 and the levels were compared with the control promoter P710 from L. mesenteroides ATCC 8293. As results, the β-galactosidase activities of the transformants were 2.73, 0.27, 37.43, and 9.25 units/mg under the P710, G3PD, 6PGD, and PPK promoters, respectively. The expression level of endogenous promoter 6PGD was superior to the heterologous P710 promoter previously used in a Leuconostoc-Escherichia coli shuttle vector. The 6PGD developed in this study can be used as the most suitable promoter for β-galactosidase expression in L. citreum EFEL2700.

Leuconostoc citreum是一种异型发酵乳酸菌，常见于各种发酵食品中。柠檬明串珠菌从韩国泡菜中分离EFEL2700已被用作宿主菌株用于生物技术的应用程序。对于用作食品级宿主以过度生产食品成分或酶，需要强大的内源性启动子来保证目标基因的高表达水平。在本研究中，使用 RNA-Seq对L. citreum EFEL2700 进行转录组学分析，并选择了三个最高表达基因的启动子：甘油醛 3-磷酸脱氢酶 (G3PD)、6-磷酸葡萄糖酸脱氢酶 (6PGD) 和磷酸酮醇酶 (PPK) ）。此后，它们被用作启动子来表达 β-半乳糖苷酶基因植物乳杆菌在WCFS1柠檬明串珠菌EFEL2700和水平与来自对照的启动子P710进行比较L.肠系膜ATCC 8293.作为结果，转化体的β半乳糖苷酶活动是2.73，0.27，37.43，和9.25单位/ mg下分别是 P710、G3PD、6PGD 和 PPK 启动子。内源性启动子 6PGD 的表达水平优于先前在明串珠菌-大肠杆菌穿梭载体中使用的异源 P710 启动子。的6PGD在本研究中开发的可以被用作最合适的启动子在β半乳糖苷酶表达柠檬明串珠菌EFEL2700。