EFFECT OF ANAEROBIC TO AEROBIC SWITCH (TWO STEP CULTIVATION) AND MEDIA COMPOSITION ON VITAMIN B12 AND HEME PRODUCTION BY Propionibacterium freudenreichii.
2025
Rajapaksa, Muditha | Helsingin yliopisto, Maatalous-metsätieteellinen tiedekunta | University of Helsinki, Faculty of Agriculture and Forestry | Helsingfors universitet, Agrikultur-forstvetenskapliga fakulteten
ABSTRACT Propionibacterium freudenreichii is, a Genetically Recognised as Safe, Qualified Presumption of Safety-certified, non-genetically modified organism, widely used in Swiss-type cheese production and showing promise for sustainable biosynthesis of vitamin B12 and heme. This study evaluated the impact of two-step cultivation (72 h anaerobic followed by 96 h aerobic fermentation) on vitamin B12 and heme production by three P. freudenreichii strains (JS 7, JS 15, and JS 16), using yeast extract lactate (YEL) and malt extract (ME) media, representing cheese-like and plant-based environments respectively. In ME medium, single-step, 72 h microaerobic fermentation was used due to pH control limitations. Two-step cultivation in YEL medium significantly enhanced vitamin B12 production of JS 7 and JS 16 strains, while JS 15 showed comparatively reduced performance under elevated oxygen conditions. The two-step approach in YEL medium was more effective for B12 biosynthesis than single-step process in ME. Iron supplementation (0.5 mM FeSO₄) reduced B12 production most notably by 44% in JS 7, but increased heme production, especially in JS 7 (64%) and JS 16 (26%) in YEL medium. Medium type and cultivation method had less influence on heme biosynthesis across strains. Analytical limitations were encountered for JS 16 grown in ME due to pelleting issues, likely linked to exopolysaccharide formation. Pseudo-vitamin B12 levels remained negligible compared to produced B12 amounts and showed no-correlation with iron supplementation. This study highlights strain-specific responses to cultivation strategy, media composition and iron supplementation, supporting the potential of P. freudenreichii as a sustainable, plant-compatible bio factory for vitamin B12 and heme, particularly relevant for vegan and vegetarian food applications.
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