January 29, 2021
Nowadays, the demand of consumers for adopting new natural agents to protect against foodborne diseases like campylobacteriosis, salmonellosis or listeriosis has triggered the search for new bio-preservatives. Vietnam is known for its wealth of safe traditional fermented foods based on spontaneous fermentation. Interestingly, these products have surprisingly long shelf life, up to several years. The present study aimed to get more insight into the bacterial diversity of traditional Vietnamese fermented foods and to develop bio-preservative agents from GRAS (Generally Recognized as Safe) bacteria, for the control of foodborne pathogens.
The composition of the microflora in traditional Vietnamese fermented foods was first examined using a metagenomic approach. This analysis showed that LAB (Lactic Acid Bacteria), especially Lactobacillus spp., were predominant in all samples. Besides, other GRAS species, such as members of the Bacillus subtilis group, were found with a noticeable abundance in samples of fermented meat, vegetables and marine products.
Then, the antibacterial compounds from LAB and members of the B. subtilis group were screened against a panel of foodborne pathogens and characterized for their potential applications. This screening selected one Lactobacillus brevis and eight Bacillus velezensis strains for their broad range antibacterial activities. The antibacterial compound from L. brevis strain HQV07 isolated from thit chua displayed activities against various bacteria, including the Gram-positive Listeria innocua, Bacillus cereus, Staphylococcus aureus and the Gram-negative Escherichia coli, Salmonella enterica, Yersinia enterocolitica and Campylobacter jeujeni. This antibacterial compound has a molecular weight of ca. 2.5 kDa and was shown to be sensitive to proteolytic enzymes and stable at 72oC for 15 min. Besides, bacilysin, a non-ribosomal peptide, was found in all B. velezensis strains by using Ultra High Performance Liquid Chromatography - Mass Spectrometry and is likely to play a major role in the antagonistic activity against Gram-negative foodborne pathogens. In conclusion, this work has unraveled two promising biopreservation agents for potential applications in the food industry.
The public defense of Huong Quynh Vu scheduled for Friday 29 January at 09:00 a.m will take place in the form of a video conference Teams