Fermentation of Soy Juice by <i>Lactiplantibacillus plantarum</i> CIRM‐BIA777 Produces Flavor‐Related and Health‐Promoting Metabolites

ABSTRACT The fermentation of plant‐based beverages, such as organic and locally produced soy juice (SJ), offers a sustainable way to develop dairy alternatives with a low carbon footprint. Lactiplantibacillus plantaru m ( Lp ) can grow on different raw materials including SJ. The aim of this study was to decipher metabolic pathways involved in (i) the adaptation of Lp . CIRM‐BIA777 during SJ fermentation, (ii) the formation of metabolites of interest in soy yogurt. The strategy was to sequence, annotate the CIRM‐BIA777 genome, to follow its metabolism using transcriptomics and metabolomics targeting carboxylic acids, carbohydrates, free amino acids, volatile compounds, and some vitamins. CIRM‐BIA777 used sucrose but only small amounts of galacto‐oligosaccharides although alpha‐galactosidase was highly expressed. Lactic, citric, and acetic acids were produced, leading to acidification and formation of a yogurt‐like structure. The strain expressed several biosynthetic pathways of health‐promoting molecules such as gamma‐aminobutyric acid, folates and, riboflavin. Fermentation also increased (i) expression of many aroma precursor genes, that is, peptidases, and (ii) the levels of some aroma compounds, for example, phenylethanol and 2,3‐butanedione, associated with floral and buttery notes, respectively, while decreasing the levels of some volatiles associated with green and beany off‐flavors, for example, hexanal. In conclusion, the fermentation of SJ by CIRM‐BIA777 improved its organoleptic and health‐promoting properties. For the first time, transcriptomics was used to investigate the molecular mechanisms involved in the formation of aroma and health‐promoting metabolites during L. plantarum fermentation in soy yogurt. This will help with the development of plant‐based fermented foods, particularly legume‐based yogurt.