SURVEY OF PROPIONIBACTERIA FOR ABILITY TO PRODUCE PROPIONIC AND ACETIC-ACIDS

Ninety strains of Propionibacterium were screened for their ability to lower the pH of maltose broths. Strains attaining a pH <5 in enriched maltose broth consisted of 12 strains of Propionibacterium acidipropi onici, 2 of Propionibacterium jensenii, and 3 of Propionibacterium tho enii. These 17 strains were further tested for their ability to produc e propionic acid on maltose, lactose, lactate, and starch and their ab ility to produce propionic acid on various concentrations of maltose a nd lactate between 0.5 and 5.0%. On the basis of these tests, strains were selected to be tested in a batch fermentor for their ability to p roduce propionic acid on a substrate of partially hydrolyzed corn. P. acidipropionici P9 proved to be one of the most productive strains and achieved concentrations of 3.25% propionic acid and 14 g/L biomass in 140 h.