Metabolomic analysis of fermented milk with Lactobacillus delbrueckii subsp. bulgaricus, Lacticaseibacillus paracasei cocultured with Kluyveromyces marxianus during storage

The metabolites produced by starter cultures potentially influence the taste, texture, and nutritional value of fermented milk. The previous study found that Lactobacillus (Lactobacillus delbrueckii subsp. bulgaricus DPUL-F36 and Lacticaseibacillus paracasei DPUL-F115) and Kluyveromyces marxianus 39 exerted good fermentation characteristics. This study aimed to monitor dynamic changes of the fermented milk metabolites produced by Lactobacillus and K. marxianus 39 during storage at 4 °C. The metabolic profiles of fermented milk involving K. marxianus 39 and Lactobacillus were changed obviously during storage. The differences in metabolites are mainly associated with amino acids and their metabolites, benzene and its derivatives, aldehydes, ketones, esters, and organic acids. The addition of K. marxianus 39 resulted in higher small peptides such as Phe-Leu-Leu, Leu-Leu-Leu-Pro-Gly, His-Gly-Val-Asp-Lys, glutamine, and L- lactic acid in the fermented milk compared to those in fermented milk by Lactobacilli only. The starter cultures combined with Lactobacillus (L. delbrueckii subsp. bulgaricus DPUL-F36 and L. paracasei DPUL-F115) and with K. marxianus 39 were more efficient in the metabolism of the amino acid (arginine, leucine, valine) and carbohydrates (beta-Lactose and sucrose) than only Lactobacillus (L. delbrueckii subsp. bulgaricus DPUL-F36 and L. paracasei DPUL-F115. The addition of K. marxianus 39 can promote the hydrolysis efficiency of protein and lactose in milk. Therefore, we speculated that L. delbrueckii subsp. bulgaricus DPUL-F36, L. paracasei DPUL-F115, and K. marxianus 39 may show some symbiotic relationship associated with metabolite utilization during milk fermentation.