Inhibition of Clostridium tyrobutyricum in cheese by Lactobacillus gasseri

A semi-hard cheese produced from milk artificially contaminated with Clostridium tyrobutyricum spores (2.5×103 mL−1) was used as a model for studying the ability of bacteriocin-producing Lactobacillus gasseri K7 (Rifr) to inhibit clostridia. The added lactobacilli did not inhibit the primary starter culture (Streptococcus thermophilus), but inhibited non-starter mesophilic lactobacilli. Late blowing as a result of Cl. tyrobutyricum outgrowth and butyric acid fermentation occurred in all cheeses however it was reduced in cheeses with added Lb. gasseri. After 6 weeks, the average amount of butyric acid was significantly higher in cheeses without added lactobacilli (1.43 vs. 0.70 g kg−1). At the end of 8-weeks ripening, 2.8×107 cfu g−1 of K7 (Rifr) viable cells were detected. Using the total DNA from cheeses with added K7 (Rifr) strain, PCR products were amplified with primers specific for Lactobacillus, Lb. gasseri and K7 bacteriocin gene.