Production of propionic acid by mixed bacterial fermentation.

VariousPropionibacteria andLactobacilli have been grown in starch based media in pure and mixed cultures to ascertain the optimum conditions for propionic acid production. A system has been identified using.Propionibacterium freudenreichii ssshermanii grown in mixed culture withLactobacillus amylophilus that yields approximately 20g/l propionic acid from a medium consisting of wheat flour and corn steep liquor. Simple processing of fermentation broths results in a product containing approximately 30% (w/w) propionic acid that may be suitable for use as a food preservative.