Valorization of fruit by-products with Propionibacterium freudenreichii: fortification of vitamin B12 in different types of fruit pomace

The food industry generates substantial quantities of by-products, with fruit pomace being particularly abundant. Highly perishable yet rich in nutrients and bioactive compounds, fruit pomace requires effective management strategies. The growing popularity of plant-based foods, driven by health, ethical, and environmental concerns, underscores the need for vitamin B12 fortification, as plants cannot synthesize this essential nutrient. This is particularly important given the increasing prevalence of cobalamin deficiency, which poses serious health risks. This study aimed to enrich pomace from blue honeysuckle berries, strawberries, and grapes with B12 via fermentation using Propionibacterium freudenreichii DSM 20271 and to optimize the culture matrix for cobalamin synthesis. Fruit by-products were assessed for safety (mycotoxins, pesticides) and nutrients (e.g., vitamins B2 and B3, cobalt) essential to Propionibacterium . Depending on the matrix, P. freudenreichii DSM 20271 consumed 25–56 % of the available sugars, with slight bacterial growth observed in all cases. Propionic acid (0.25–2.42 g/kg) and vitamin B12 (13.91–39.71 μg/kg) were produced in all variants. The optimized ratio of strawberry pomace (65 %) and grape pomace (35 %) increased B12 synthesis to 49.44 μg/kg. The results confirm the possibility of developing a strategy for food fortification with cobalamin using P. freudenreichii , in line with sustainable development. • Fruit pomace can be enriched with vitamin B12 using P. freudenreichii. • Fruit pomace provides nutrients essential for the metabolism of P. freudenreichii. • Optimizing the ratio of fruit pomace components increases vitamin B12 production. • Vitamin B12-enriched fruit pomace has potential for use in plant-based foods. • Fermentation is a promising method for valorizing fruit by-products.