Abstract
Lactococcus lactis subsp. cremoris is a lactic acid bacterium commonly used in the cheese manufacturing industry. It is known to produce antibacterial peptides and has recently received attention for its role as a probiotic strain. Here, we report the isolation of a new strain, Lactococcus lactis subsp. cremoris RPG-HL-0136 (RPG0136) from dried compost, which exhibits strong antibacterial activity. When RPG0136 was fed to mice, it increased the intestinal population of two beneficial bacteria, Lactobacillus and Bifidobacterium, whereas it decreased the intestinal population of two harmful bacteria, Bacteroides and Enterobacter. In addition, it increased the concentration of short-chain fatty acids, including acetic acid, propionic acid, and butyric acid, with a simultaneous decrease in pH, and accelerated the catabolic degradation of proteins, lipids, and starch. Lastly, RPG0136 increased the plasma IgG and intestinal mucosal SIgA concentrations and upregulated Reg3r, MUC1, and MUC2 expression to improve the intestinal mucosal immune function. The results of this study suggest that RPG0136 is a potential probiotic strain that supports the growth of a beneficial microbiome by promoting the synthesis of organic acids and enhancing intestinal immune function.
Highlights
The intestine is a major site for the digestion and absorption of nutrients and is colonized by various microorganisms [1]
We identified a new strain of Lactococcus lactis subsp. cremoris from dried compost based on its morphological characteristics and antibacterial activity
To determine the effects of RPG0136 on the population of beneficial and harmful microorganisms, RPG0136 or no bacteria were orally administered to mice, and the number of colonies formed by intestinal Lactobacillus, Bifidobacterium, Bacteroides, and Enterobacter were counted by culture on selective media using the plate counting method (Fig. 2)
Summary
The intestine is a major site for the digestion and absorption of nutrients and is colonized by various microorganisms [1]. Numerous studies have reported that the intestinal microflora regulates the nutrient metabolites of the host, and interacts with the host immune system and influences the progression of diseases [2]. External stimuli, such as excessive food or drugs, disturb the intestinal environment and cause an imbalance in the population of intestinal symbiotic microorganisms that affect metabolite production and host immunity, such as Lactobacillus, Enterococcus, and Streptococcus, and Enterobacteria; this may lead to Lactococcus lactis is a gram-positive lactic acid bacterium widely used to coagulate milk in the cheese and butter industry, and its use has been approved owing to its designation as a generally recognized as safe bacterium. As a food bio-preservative, nisin acts as a broad-spectrum bacteriocin against most gram-positive food-borne bacteria [12,13,14]
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