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Gewählte Master / Diploma Thesis:

Katharina Dürr (2014): Identität, Charakteristik und Sicherheit potentieller Milchsäurebakterien-Starterkulturen für montenegrinischen Käse.
Master / Diploma Thesis - Institut für Lebensmittelwissenschaften, BOKU-Universität für Bodenkultur, pp 185. UB BOKU obvsg

Data Source: ZID Abstracts
Abstract:
Starter cultures for cheese are lactic acid bacteria, which induce the acidification of milk. They also possess several other important functions such as the formation of flavour and texture and ripening due to proteolysis. Lactococcus lactis is one of the most frequently applied starters. Starter cultures have to be well-defined and identified. Some of them are able to produce antibacterial substances (bacteriocines) that inhibt the growth of pathogens and spoilage microorganisms. Cultures may not carry antibiotic resistances, pathogenic factors or genes encoding enzymes to form biogenic amines. The aim of this work was to investigate lactic acid bacteria isolated from Montenegrian cheese for their suitability as starter cultures. In particular, 40 Lactococcus lactis isolates were tested in a smear-spot-test for their antimicrobial activity, they were further screened for decarboxylase genes and bacteriocin activities. Additionally, their antibiotic resistance to nine selected antibiotics of human and veterinary importance was checked using the microdilution broth method. It was shown that 25% of the isolates had an inhibitory activity against Staphylococcus spp. and all isolates slightly inhibited the groth of Listeria spp. The existence of genes encoding for bacteriocins could not be confirmed. A cluster analysis of other lactic acid bacteria (especially Lactobacillus spp.) was done to show their similarity profiles. Antimicrobial susceptibility was tested using the disk diffusion method. The similarity analysis yielded less identical results than the sequencing made before. Enterococcus spp. play an important role as non-starter cultures in cheese. However, they can carry antibiotic resistance genes and may transfer them to other bacteria, for example to pathogens. This is a potential risk factor. Thus Enterococcus spp. strains showing the presence of antibiotic resistance were screened for resistance genes.

Beurteilende(r): Kneifel Wolfgang
1.Mitwirkender: Mayrhofer Sigrid
2.Mitwirkender: Domig Konrad

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