Liver function and protection

Lactococcus lactis is one of the most common organisms used in bacterial drug delivery system. Lactococcus lactis is a food-grade bacterium that is widely used in the dairy industry. It is a Gram-positive bacterium and therefore lacks endotoxic lipopolysaccharides (LPS) which are associated with commonly used Gram-negative bacteria . It is also non-invasive and non-commensal and thus has less potential to trigger immunotolerance or side effects upon prolonged use. The bacterium has an established safety profile through its long use in fermented dairy products and is considered as a GRAS (generally recognized as safe) microorganism. During the last two decades, significant advances have been made in the field of lactococcal genetics and protein expression systems. The most commonly used system is the nisin-controlled gene expression (NICE) system, containing the nisin promoter. Consequently, we have seen the emergence of new areas for the application of engineered L. lactis for protein expression, gene delivery, vaccine delivery, and therapeutic drug delivery.

In the present project, since the oral table administration of GSH and SAM have some disadvantages, such as low stability and short life span, here we tried to develop a novel in-vivo strategy of produce and deliver them simultaneously by using NICE system. In the experiment, two-functional GSH synthetase gene (gshF) and SAM synthetase gene (metK) were in tandem inserted into the expression vector (pNZ8148), and the resulted plasmid (pNZ8148-SG) was employed to construct the target vector pNZ8148-SGC by introducing adhesion factor gene (cwaA). This target vector was transformed to get recombinant Lactococcus lacti, which was employed to produce our “smart yogurt”.

The project is outlined with two stages：

Stage AConstruction of Lactococcus lactis NZ9000/pNZ-SGC

Stage BPreparation of smart yogurt with our constructed Lactococcus lactis