Human milk oligosaccharides have received widespread attention due to their unique probiotic effects. The composition and structure of oligosaccharides from the milks of different mammals are different. Some probiotics represented by bifidobacteria evolve a relatively complete metabolic mode of milk oligosaccharides. Compared with other prebiotics, milk oligosaccharides show more health benefits such as inducing the colonization of bifidobacteria and increasing the diversity of intestinal flora.

The growth, acid production and changes in viable cell count of 8 strains of Leuconstoc mesenteroides were measured in chemically defined medium (CDM) with different carbon sources or skim milk. The results showed that there were significant differences in the growth of these strains in CDM with lactose or galactose as the single carbon source. Strains LM1, LM2, LM4 and LM8 grew well in CDM with lactose as the single carbon source. Strains LM2, LM3, LM5 and LM8 had stronger vitality in CDM with galactose as the single carbon source, but their growth was weaker than that in the presence of lactose. In skim milk, the viable cell count of all experimental strains increased obviously in the early fermentation stage. After 8 h, their growth entered the stable phase, and the pH value at the end of fermentation was above 6.0. While the differences in genes related to lactose and galactose metabolism were preliminarily compared among the strains in this study, the correlation between genes and phenotypes needs to be further analyzed based on lactose hydrolase activity and lactose and galactose residues.

ε-Polylysine is widely used as a natural biological preservative in meat, dairy products and other foods for its characteristics of high safety, stability, efficiency, solublity in water and broad-spectrum antibacterial activity. In this paper, physiological and biochemical characteristics of Streptomyces albulus UN2-71, a strain capable of producing ε-polylysine, were studied. The ε-polylysine production increased from 1.64 to 2.37 g/L after optimization of fermentation conditions. The optimized conditions were defined as: 30 mL of the liquid medium in a 250 mL shake flask, inoculum size 10%, temperature 30 ℃, shaking speed 150 r/min and initial fermentation pH 7.0.