Lactic acid bacteria (LAB) are largely used in coculture in food fermentations. The use of different LAB species or strains as starter can bring complementary functionalities participating to the overall quality of fermented food. Fermentation can benefit from LAB’s interactions, resulting in a more efficient fermentation. Few is known about positive LAB’s interactions that are beneficial to fermentation processes. Lactobacillus delbrueckii CIRM-BIA865 (Ld865) and Lactiplantibacillus plantarum CIRM-BIA777 (Lp777) are two strains able to ferment soy juice (SJ). In SJ monocultures, Ld865 was obligately homolactic and released 17 amino acids while Lp777 was facultatively heterofermentative and consumed 10 of the 17 amino acids released by Lp777. When these strains were cocultivated in SJ, the fermentation time was reduced of 30% compared to monocultures. Furthermore, Ld865 cells were four times shorter in coculture than in monoculture and Ld865 population increased tenfold. In this work, we aimed to reveal how Lp777 and Ld865 interact with each other to improve SJ fermentation. Thanks to transcriptomic and metabolic analyses carried out along the kinetic of fermentation, we compared the adaptations of their metabolisms in coculture versus in monoculture. Transcriptomics data showed, among others, that Lp777 induced the expression of genes involved in the regulation of oxidation-reduction potential at a higher level in coculture than in monoculture. The oxidation-reduction potential measured in cocultured SJ was intermediate between those measured in monocultures. The better regulation of the oxidation-reduction potential in coculture seems to involve methionine released by Ld865. Lp777 and Ld865 could also cooperate to metabolize carbon. In conclusion, LABs with distinct and complementary metabolic profiles can be useful to take over SJ fermentation. This work opens new avenues for strains selection intended to cooperate in plant-based fermentation. Several examples of positive LAB’s interactions that are beneficial in SJ fermentation will be provided during this communication.