Effects of pH and Sodium Chloride on the Interactions Between Geotrichum candidum and Brevibacterium linens

The interactions between 14 isolates of Geotrichum candidum and 14 isolates of Brevibacterium linens were analyzed to understand their behavior in cheese making. Mixed cultures were grown in a peptone broth containing various NaCl concentrations and various pH. The pH and the concentration of NaCl affected the interactions. According to the pH, in many strain pairs, B. linens strongly stimulated the growth of G. candidum, and this interaction varied depending on the pH. Inhibition occurred only at pH 5.0. In fewer pairs, G. candidum moderately stimulated the growth of B. linens, and the optimal pH for this stimulation and the inhibition were 7.0 and 5.0, respectively. The number of pairs in which the growth of G. candidum was increased by the presence of B. linens was highest with 1.5% added NaCI. With increasing NaCl concentration, stimulation of the growth of B. linens by G. candidum decreased because of the sensitivity of G. candidum and resistance of B. linens to NaCl. Brevibacterium linens isolates were similarly grown in the presence of filtrates of stationary phase cultures of G. candidum. The filtrates exhibited effects analogous to, but larger than, those of the strains from which the filtrates were prepared.