Use of conductance to detect bacteriocin activity

The inhibitory activity of a bacteriocin produced by Lactobacillus delbrueckii subsp. lactis G4 (Bac+) in milk was investigated by using conductivity measurements. The bacteriocin showed an inhibitory action toward some strains belonging to L. delbrueckii subsp. bulgaricus species. A delay in detection time (δDT) of two milk cultures sensitive to bacteriocin, grown in the presence of preformed bacteriocin, was observed. An inactivation as well as a modified growth rate of the sensitive cultures due to bacteriocin activity might explain the δDT, as indicated by longer generation time (tg). Cells showed the highest sensitivity to bacteriocin during the log phase of growth that corresponded to the beginning of the acceleration of the conductance curve (DT).