Objective: In this study, 20 Bacillus spp. isolates, which have been isolated from 13 different bread flour, whether they were rope factor has been aimed to investigate and then inhibitory effect of Lactobacillus rhamnosus, which have probiotic properties, has been aimed to examine on the Bacillus isolates.

Materials and Methods: The inhibitory effect of L. rhamnosus on Bacillus spp. was investigated in vitro both in agar diffusion and in liquid medium using the cell and supernatant of 24-hour and 48-hour L. rhamnosus culture. In addition, antibacterial influence of L. rhamnosus on Bacillus subtilis was tested in bread dough.

Results: The inhibitory effect of L. rhamnosus on Bacillus spp. was detected in 6 of the 20 Bacillus isolates in liquid medium. The results obtained by the agar diffusion method revealed that 6 Bacillus sp. isolates showed resistance to the supernatant of L. rhamnosus and 5 Bacillus sp. isolates showed resistance to L. rhamnosus cell at the end of 24-hour-incubation. Standing isolates remained the same and all isolates in cell were susceptible at the end of 48-hour-incubation with the supernatant. The amount of B. subtilis was raised from 1.3x104 CFU/g to 1x109 CFU/g in the B. subtilis added dough. However, the number of B. subtilis was 2.9x104 CFU/g at the end of 24 hours in L. rhamnosus simultaneously added dough. During the counting of rope in flour, which has been used in study, maximum contamination was seen in oven flour, minimum contamination also was seen in organic flour.

Conclusion: The inhibitory effect of L. rhamnosus to the rope agent Bacillus spp. was observed in agar diffusion, liquid medium and the dough. The results of this study emphasized the use of probiotic bio-protects beneficial for human health as additives in bread instead of the use of harmful chemicals as additives.