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Dairy bacteriocins

  • Publisert 31.12.2002
  • Sist oppdatert 30.03.2011
The overall objective of this project is to gain new and important information on propionibacteria (PAB) as starter culture and protective culture in general, and also establish new information and criteria for application of PAB in dairy products with emphasis on their antimicrobial effect. The overall goal is to establish new PAB and PAB in combination with LAB to be used in industrial proceses in dairy foods.

Frontpage report

In order to achieve this objective the following tasks will be carried out:

  1. Screening and characterization of new PAB: Taxonomy and metabolictraits. Growth kinetics and effect on temperature, salt and growth media.
  2. Screening characterization of antimmicrobial activity of PAB against fungi and bacteria.
  3. Combine PAB and LAB and test for synergistic effects.
  4. Investigate PAB as starter culture.
  5. Investigate LAB as protective culture.
  6. Investigate the cell free extracts of PAB/LAB as antimicrobial agent in food.

 

Most important results:

 

  • Approximately 130 isolates of propionibacteria (PAB) has been isolated and taxonomically characterized (16S RNA DNA sequences , metabolic and phenotypic properties) and a PAB culture collection has been established that is available to all participants. All the strains is also distributed among the four participants for functional studies. The PAB culture collection has been established as a resource for the participants to be used in the project and this collection can also be used by the participants in future collaborator work and application. The eventual commercial use of these cultures is managed by a contract that has been signed by all partners.
  • The antimicrobial potency of the PAB strains has been evaluated and is finished. Arla has investigated the antifungal activity. Danisco has investigated the inhibitory potency of PAB against Gram negative bacteria. Tine/NLH have tested the antagonistic activity against Gram-positive bacteria. The results clearly demonstrate that a large number of the PAB isolates are able to kill /inhibit growth of many microorganisms.
  • It has been shown that many PAB are able to produce CLA (conjugated linoleic acid) some at high concentrartion.
  • Important industrial properties such as tolerance to salt, growth and growth media, temperature etc. have been investigated
  • Two PAB bacteriocins have been purified and characterized on the amino acid level and also the bacteriocin genes have been sequenced (see references). This is the first PAB bacteriocins that has been characterized on such detailed level. In addition two more antimicrobial compounds have been isolated and partly characterized .In order to apply the culture in food an extensive study of functional growth characteristics of selected PAB have been performed. The effect of temperature, pH and salt on growth kinetics has been elucidated.
  • 4-7 potential interesting PAB for commercial use have been identified and testing of these are under way.
  • The cheese trials have been finalized at Tine and Arlafoods with some of the new isolated PAB. Results have been obtained that will lead to additional trials in future cheese trials in order to establish new combination of starter cultures. In particular the new strains T5 and T114 showed promissing results to be implemented in future cheese products.
  • Some PAB isolates in combination with certain lactobacilli have been shown produce strong antifungal / antimould activity relevant for problems related to cheese.
  • Inhibition of moulds has also been found with PAB strain LMG2868 and with a combination of PAB DC2053 in combination with Lb. Rhamnosus Lc705 in yogurt simulated conditions.
  • One PhD student (Dag A. Brede) is associated to the project and NI funds will contribute significant to his PhD thesis. One person (Inger Ødegård at TINE) has finished her cand. Scient. thesis within the NI project.
Prosjekttid: 01.11.2001 - 31.12.2002


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