Microbial co-cultures within self-generated cellulose scaffolds offer toolkits for controlling plant juice fermentation

The aim of this study was to establish synthetic co-cultures within self-generated cellulose scaffolds (SC-CS), thereby providing robust toolkits for the controlled fermentation of plant juices. Our approach combined the growth of a cellulose scaffold with the simultaneous integration of microbial cells carrying target metabolic functions. We found that Lactiplantibacillus plantarum C2, Levilactobacillus brevis POM4, and Schizosaccharomyces pombe JB6C2 were compatible with Komagataeibacter xylinus DSM2325, enabling co-culture and the formation of mixed-species cellulose pellicles. When SC-CS were employed as inocula in subsequent incubations, the microbial composition of the biofilm was preserved both in nutrient-rich synthetic media and in a substrate mimicking food-processing environments (carrot juice), although differences arose in the timing of floating film formation. During carrot juice fermentation, sugar consumption and metabolite production by the SC-CS partially reflected the primary metabolism of the individual strains associated with K. xylinus DSM2325. Clear examples of microbial interaction and cross-feeding were also observed. Microbial interactions within each SC-CS also played a pivotal role in shaping the profiles of free phenolic compounds and volatile compounds in fermented carrot juice.