Characterization of strains of Propionibacterium freudenreichii for fermentation of plant based raw material

Propionibacterium freudenreichii is among the most important microorganisms for industrial applications due to their ability to biosynthesize valuable metabolites, including vitamin B12, propionic acid, trehalose, and bacteriocins, on various substrates. P. freudenreichii is the only food-grade microorganism recognized for its ability to synthesize vitamin B12, However, its application in large-scale food production faces challenges due to its intrinsically slow growth rate and sensitivity to acidic environments. To overcome these limitations, previous studies have predominantly utilized sterilized grain substrates. The objective of this study was to characterize some technologically relevant phenotype traits of 14 strains of P. freudenreichii previously isolated from different cheeses, and to investigate their growth rate and fermentation profiles of P. freudenreichii in two standard cultivation substrates De Man, Rogosa and Sharpe (MRS) and Yeast Extract Lactate (YEL). Specifically, the β-glucosidase and phytase activity of the strains were assessed due to their roles in improving the bioavailability of nutrients and the overall nutritional value of plant-based foods. After monitoring the enzymatic activities and measuring kinetics of all 14 strains of P. freudenreichii in YEL and MRS broths during 72 hours of fermentation, eight strains demonstrating superior growth and metabolic activity in preliminary tests, were selected for further fermentation of oat and faba bean food-like media. From these food-based substrates pH, optical density (OD600), and plate counts were monitored over a 72 hours fermentation period. This comprehensive evaluation was able to identify the most promising strains of Propionibacterium freudenreichii for future biofortification of plant-based foods, thereby enhancing their nutritional value.