Production of propionic acid by mixed cultures ofPropionibacterium shermanii andLactobacillus casei in autoclave-sterilized whey

Abstract

Pure cultures of Propionibacterium freudenreichii ss. shermanii did not grow in autoclave-sterilized cheese whey (12I~ 15 psi, 20 rain) at whey concentrations greater than 2% (w/v) spray-dried sweet dairy whey. Propionic acid was produced from autoclave-sterilized whey by growing P. shermanii in mixed culture with LactobacilIus casei. In medium containing 5-12% autoclaved whey solids and 1% yeast extract, the mixed culture produced 1.3-3.0% propionic acid, 0.5-1.0% acetic acid, and 0.05 0.80% lactic acid. All the lactose was consumed. Using pH-controlled fermentors (pH = 7.0), mixed cultures produced at least 30% more propionic acid than cultures in which pH was not controlled.