Metabolomics study on fermentation of Lactiplantibacillus plantarum ST-III with food-grade proliferators in milk.

Milk is a naturally complex medium that is suitable for the growth of most lactic acid bacteria. Unfortunately, Lactiplantibacillus plantarum ST-III, a probiotic strain of bacteria used to produce fermented foods, grows poorly in milk without supplementation. To solve this problem, we used fresh pineapple and mung bean juice to develop an edible proliferator for L. plantarum ST-III. Our comparative analysis of changes in metabolomics before and after fermentation revealed that amino acids, dipeptides, nucleotides, and vitamins were the most consumed compounds, implying the mechanism of proliferation. These results, in combination with Kyoto Encyclopedia of Genes and Genomes metabolic pathway analysis, were used to screen substances that could promote the growth of L. plantarum ST-III in milk. To explore which component of the proliferator was required for L. plantarum ST-III growth, we supplemented milk with several combinations of substances from the proliferator that were identified as promoting growth. The experimental results showed that if any of these substances were missing, the concentration of viable bacteria was lower. The highest concentration of viable bacteria could only be obtained when all the substances were added to the milk. Compared with the control, the concentration of viable bacteria was about 32-fold higher in milk that contained the proliferator. Thus, the study proves that milk primarily lacks available amino acids, dipeptides, uracil, xanthine, nicotinamide, and manganese, which are necessary for the growth of L. plantarum ST-III.