Valorization of fruit by-products: Vitamin B12 fortification in fruit pomace using a co-culture of propionic and...

The agri-food industry generates large quantities of by-products, e.g., fruit pomace from juice and wine production, which represent underutilized sources of valuable compounds. The popularity of plant-based foods is steadily increasing due to growing concerns about human health, animal welfare, and environmental sustainability, highlighting the need for vitamin B12 fortification - plants cannot synthesize this essential micronutrient. This challenge is particularly relevant given the growing prevalence of B12 deficiency and its associated health risks. The aim of this study was to enrich pomace from blue honeysuckle berries, strawberries, and grapes with B12 via co-fermentation using Propionibacterium freudenreichii DSM 20271 and Lactiplantibacillus plantarum ATCC 10241 (selected based on screening tests, including the co-existence test of P. freudenreichii-different LAB species), and to optimize the pomace matrix for cobalamin biosynthesis in co-culture conditions. The pomace matrices were characterized with respect to carbon and nitrogen sources, as well as cobalamin biosynthesis precursors, including cobalt, riboflavin, and niacin. Nearly complete utilization of available carbon sources was observed in all matrices. B12 (13.91-39.71 μg/kg) and propionic acid (0.73-4.31 g/kg) were produced in all pomace-based media. Optimization experiments indicated that strawberry and grape pomace were the most suitable substrates for B12 synthesis, whereas propionic acid production was primarily associated with strawberry pomace. These findings demonstrate the feasibility of using co-cultures of propionic acid and lactic acid bacteria to enrich fruit pomace with B12. This approach offers a promising strategy for developing B12-fortified plant foods from fermented and edible fruit pomace, thereby supporting sustainable development and zero-waste principles.