Growth of a Mixed Species Lactic Starter in a Continuous "pH-Stat" Fermentor

Optimum growth conditions for mixed species starter FDs 0172 in skim milk, whey medium, and tryptone medium at 25 C in a “pH-stat” continuous fermentor were investigated. Specific growth rate and productivity were found to be influenced both by the medium and the pH value. Highest productivity was found in skim milk medium between pH 5.5 and 5.9. Lactic acid-producing activity of harvested cells decreased by continuous cultivation at pH values lower than 5.9 to 6.1, especially in tryptone and whey medium. Bacterial balance, CO₂ production, and aroma formation were comparable to the control in skim milk and whey medium at any pH, but differed significantly for cells grown in tryptone medium.