# Lactose-Free Fermented Milk Production Using Lactococcus lactis NK24 and NK34 with Immune-Enhancing Effects on RAW 264.7 Cells

## TL;DR

This study shows that lactose-free fermented milk made with Lactococcus lactis strains can boost immune responses in cells, similar to known immune stimulants.

## Contribution

The study introduces new Lactococcus lactis strains (NK24 and NK34) that produce lactose-free fermented milk with immune-enhancing properties.

## Key findings

- Lactose-free fermented milk stimulated NO production and phagocytic activity in RAW 264.7 cells.
- The milk increased mRNA levels of iNOS, COX-2, and proinflammatory cytokines.
- It also promoted protein expression and phosphorylation linked to immune pathways like NF-kB and MAPK.

## Abstract

This study aimed to produce lactose-free fermented milk using probiotic Lactococcus lactis strains and to investigate the immune-enhancing effects of fermented milk. Lactose-free milk was fermented using Laticaseibacillus rhamnosus GG (LGG), L. lactis NK24, and L. lactis NK34. The pH, TA, viable lactic acid bacterial counts, and physicochemical properties of lactose-free fermented milk were recorded over 28 days under refrigeration. Each water-soluble extract of lactose-free fermented milk stimulated NO production, phagocytic activity, and induced morphological changes in RAW 264.7 cells, similar to the LPS treatment group. Additionally, the mRNA levels of inducible nitric oxide (iNOS), cyclooxygenase-2 (COX-2), and proinflammatory cytokines increased. Furthermore, each sample promoted protein expression of iNOS, and COX-2 and phosphorylation of p38, p65, JNK, and ERK. Therefore, lactose-free milk fermented by L. lactis NK24 and L. lactis NK34 can enhance the immune response via nuclear factor-kB (NF-kB) and mitogen-activated protein kinase (MAPK) activation and has the potential for development as a functional food.