Enhanced Bacteriocin Production by Propionibacterium thoenii in Fed-Batch Fermentation ^‡

Synthesis of the bacteriocin propionicin PLG-1 as well as culture growth and organic acid production by Propionibacterium thaenii P127 were followed in fed-batch fermentations conducted for 504 h in a sodium lactate broth. Average concentrations of viable cells were higher in two small-scale fed-batch fermentations than in batch fermentations: 2.2 × 10⁹ cells per ml versus 3.7 × 10⁸ cells per ml. Propionic acid concentration averaged 35.8 g/liter at the end of fed-batch fementation, and maximum bacteriocin titers were 184 and 146 AU/ml in the two fed-batch fermentations. After reaching the maximum value, bacteriocin activity dropped sharply upon continued incubation. Large quantities of propionicin PLG-I could be obtained in large-scale fed-batch fermentation, but the concentration (100 AU/ml) was lower than in the small-scale fermentations. Fed-batch fermentation shows promise as a method to obtain high concentrations of bacteriocin from the propionibacteria.