Incidence and characterisation of Bacillus cereus bacteriophages from Thua Nao, a Thai fermented soybean product.

Bacillus cereus is considered to be an important food poisoning agent causing diarrhea and vomiting. In this study, the occurrence of B. cereus bacteriophages in Thai fermented soybean products (Thua Nao) was studied using five B. cereus sensu lato indicator strains (four B. cereus strains and one B. thuringiensis strain). In a total of 26 Thua Nao samples, there were only two bacteriophages namely BaceFT01 and BaceCM02 exhibiting lytic activity against B. cereus. Morphological analysis revealed that these two bacteriophages belonged to the Myoviridae. Both phages were specific to B. cereus and not able to lyse other tested bacteria including B. licheniformis and B. subtilis. The two phages were able to survive in a pH range between 5 and 12. However, both phages were inactive either by treatment of 50°C for 2 h or exposure of UV for 2 h. It should be noted that both phages were chloroform-insensitive, however. This is the first report describing the presence of bacteriophages in Thua Nao products. The characterization of these two phages is expected to be useful in the food industry for an alternative strategy including the potential use of the phages as a biocontrol candidate against foodborne pathogenic bacteria.

Bacteriophage control of Salmonella Typhimurium in milk.

This study was designed to evaluate the effect of bacteriophage P22 on the inhibition of growth of Salmonella Typhimurium. The P22 belongs to Podoviridae family consisting of a hexagonal head and short tail. The inhibitory effect of phage in milk was noticeable at the early storage period, showing more than 3 log reduction at 4 h and day 3. The pH values of milk treated with P22 were significantly decreased from 6.7 to 6.3 after 24 h incubation at 37 °C, while no significant changes in pH values were observed for the control and bacteriophage treatment throughout the storage at 4 °C for 12 days. The slight color changes were observed in the control and bacteriophage treatment throughout the storage at 4 °C for 12 days and 37 °C for 24 h. These results provide useful information for enhancing microbiological safety and quality of milk and designing effective bacteriophage-based control in food system.

Significance of bacteriophages in fermented soybeans: A review.

Bacteriophages are ubiquitous and have been reported to have been found in many food products. Their presence is important as they have the ability to interact with their bacterial host in food matrices. Fermented soybean products, one of the most widely consumed ethnic foods among Asian people, are prepared naturally and include Japanese Natto, Indian Kinema, Korean Chongkukjang and Thai Thua Nao. This review highlights bacteriophages which have been isolated from fermented soybean products and also includes an overview of their diversity, occurrence as well as their significance.