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Use of phages to remove the odour-producing bacteria from meat

Principal Supervisor: Professor Martha Clokie - Department of Infection Immunity and Inflammation

Co-supervisor: Prof Paul Monks - Chemistry

PhD project title: Use of phages to remove the odour-producing bacteria from meat

University of Registration: University of Leicester

Project outline:

Proposal for the isolation of phages against odour producing bacteria found in meat

Background

When vacuum-packed meat is first opened it is not uncommon for consumers to smell a bad odour. This smell can discourage consumers as they may presume the meat has gone off but typically washing the meat helps to remove the smell. However, if consumers are unaware of this it can lead to economic loss and negatively impact the commercial product brand,

Contamination of meat by odour-producing bacteria such as Lactobacilli and Leuconostoc may occur at any stage of the production line. Sources may also include water, facilitates, equipment and manipulators. Consequently, it does make it difficult to pin point the exact source of bacterial contamination. Most meat is vacuum packed with the aim of protecting the meat products from contact with oxygen from the air, and limiting the growth of bacteria. Although this limits the level of growth of microbes it does promote the growth of lactic acid producing bacteria. These bacteria are responsible for the bad odour and can also contribute to meat spoilage. Initially when the meat is packaged the bacteria are present at levels below the limit of detection and therefore missed but bacterial numbers increase during storage as they able to grow at refrigeration temperatures. This results in a significant amount of meat being returned to the shop/supplier with consequent economic impact and wastage within the food chain.

A promising method to remove these bacteria is to exploit bacteriophages (phages), which are naturally occurring viruses that are able to kill bacteria. The FDA has classed phages, as safe and commercial phage products are available on the market, such as a phage cocktail to prevent Listeria in ready to meat meal, meat and fruit. Consequently due to their safe status, phages could be used on meat products to prevent growth of lactic acid producing bacteria and consequently the production of bad odours. This PhD project will provide the student with a multidisciplinary training, and give them experience to the industrial environment.

Project aims

Title: Isolation and characterisation of phages targeting odour-producing bacteria in vacuum packed meat.

Specific aims are:

  • Isolate phages against odour producing bacteria by screening meat-packaging samples, as typically phages are isolated in locations where the target bacteria are prevalent.
  • Characterise isolated phages by transmission electron microscope, determining host range and infection cycle.
  • Phages with the broadest host ranges will be sequenced.
  • From isolated phages, establish the optimum phage cocktail that can target the most prevalent odour-producing bacteria and significantly reduce bacterial count.
  • Carry out mass-spectrometry to determine the phages have removed the bacteria that are causing the offensive odours
  • Establish the best method to apply phages to prevent bacterial growth. The best application would be during packaging of the meat to ensure when consumers open the vacuum packed meat they do not smell any bad odours.
  • Possibilities include: - Phages could be sprayed into films and so after vacuum packaging it would prevent growth of lactic acid producing bacteria. - Meat could be sprayed before vacuum packaging to prevent odour formation.

BBSRC Strategic Research Priority: Food Security

Techniques that will be undertaken during the project:

  • Microbiology, bacteria and phage isolation and culture
  • PCR and sequencing of bacteria and phage genomes
  • Bioinformatic analysis and comparative genomics
  • Mass-spectrometry, looking at volatile organic compounds released from meat

Contact: Professor Martha Clokie, University of Leicester