The inhibitory effects of Lactobacillus casei and Lactobacillus helveticuson Bacillus species isolated from raw milk in various salt concentrations

Nineteen strains of Bacillus were isolated and identified from III samples of raw milk. The inhibitory effects of Lactobacillus casei and Lactobacillu s helveticus on strains of Bacillus were studied. Pie inhibitory effects we re evaluated (using the well diffusion method) on nutrient agar, with NaCl added at concentrations of 40, 45, 50, 55, 60 and 65 g/L. Lactobacillus cas ei inhibited 16 strains of Bacillus on nutrient agar without salt, and 18 s trains in the presence of salt. When the salt concentration was 6.5%, the i nhibitory effect decreased, and L. casei inhibited only eight strains of Ba cillus (Bacillus cereus, Bacillus sphaericus, Bacillus licheniformis, Bacil lus macerans, Bacillus firmus, Bacillus coagulans, Bacillus polymyxa and Ba cillus stearothermophilus). Lactobacillus helveticus formed the inhibitory zones against five strains of Bacillus on nutrient agar without salt, but w ith 4% NaCl concentration, it showed an inhibitory effect on 13 strains; a further two strains were inhibited in the presence of 4.5 and 5.0% salt. In 5.5% NaCl, the same 15 strains were inhibited by L. helveticus, whilst in 6 and 6.5% salt, the inhibitory effect decreased and only six and seven str ains were affected, respectively. The maximum inhibitory effect with both L . casei and L. helveticus was observed in the presence of 4.5-5.5% salt.