ABSTRACT
Lactobacillus helveticus and Propionibacterium acidipropionici were grown in pure and mixed cultures in a complex medium to assess the associative interaction. The specific growth rates, substrate consumption coefficient, substrate utilization and product formation rates were determined in each case. Propionibacterium acidipropionici utilized glucose preferably when it grew in a medium containing a mixture of glucose and lactate. Its growth rate was higher on glucose than on lactate in pure culture. However, lactic acid was the substrate utilized by propionibacteria in the associative growth. The fast pH reduction produced by the growth of lactobacilli and the slow lactate utilization by propionibacteria in mixed culture determined the inhibition of propionic acid bacteria in associative growth.
