The use of the pathogen-specific bacteriophage BCP8-2 to develop a rice straw-derived bacillus cereus-free starter culture

The purpose of this study was to develop a rice straw-derived Bacillus cereus (B. cereus)-free starter culture for traditional soybean fermented products using a B. cereus-specific bacteriophage, BCP8-2. To determine the optimal medium that supports the growth of rice straw-derived microorganisms and BCP8-2 activity, 5 different culture media were tested. The 5% ground bean (GB) medium was selected for further study. No B. cereus was detected in the BCP8-2-treated rice straw in GB medium, whereas B. cereus at a level of 107 CFU/mL was recovered in the no-phage control. The total bacterial count reached approximately 109 CFU/mL regardless of phage addition. When the 16S rRNA sequence-based microbial community was monitored using denaturing gradient gel electrophoresis (DGGE) and pyrosequencing, a similar microbial community was observed in the phage-treated and control samples. In conclusion, we demonstrate that phage can be used to prepare a rice straw-derived B. cereus-free starter culture with minimal effect on natural microflora.