Revealing the regulatory mechanisms of amino acids in co-fermentation of jujube pulp by Lachancea thermotolerans and Lactiplantibacillus plantarum: insights from flavor characterization and metabolomic analysis.

In this study, three amino acids (arginine, lysine and threonine) preferred by Lachancea thermotolerans and Lactiplantibacillus plantarum were added to jujube pulp co-fermentation system to investigate the different regulatory mechanisms. A comprehensive profiling of fundamental physicochemical metrics, characteristic volatile organic compounds (VOCs), non-volatile metabolites, and relevant metabolic pathways was conducted. The results demonstrated that the supplementation of amino acids enhanced microbial growth, improved sugar utilization, and accelerated the accumulation of organic acids. Twenty characteristic VOCs were identified. Arginine primarily regulated the formation of esters and aldehydes, such as phenylacetaldehyde and isoamyl acetate. Lysine mainly affected short-chain alcohols and acids production, represented by 3-methyl-1-butanol and isobutyric acid, while threonine predominantly influenced alcohols and esters, including phenethyl alcohol and ethyl acetate. All the three amino acids stimulated glycolysis, starch and sucrose metabolism, and amino acid biosynthesis, each amino acids exhibited distinct regulatory effects. Arginine primarily modulated arginine and proline metabolism. Lysine enhanced glucose and fructose consumption more efficiently, while threonine supported the generation of new alcohols and ketones via the Ehrlich and propionyl-CoA pathways. Additionally, aspartate, a key metabolite in amino acid biosynthesis, played an essential role in maintaining nitrogen balance in jujube pulp fermentation system. These findings can offer a theoretical basis for nitrogen management strategy in industrial production of Lachancea thermotolerans and Lactiplantibacillus plantarum co-fermentation.