| Abstract [eng] |
Consumers today are concerned about food additives, unnaturalness, and the health benefits of processed. Products without the addition of any chemical preservatives are becoming more and more attractive. Possible alternative to address this concern is the synthesis of antibacterial peptides, also known as bacteriocins. Bacteriocins are antimicrobial peptides synthesised by the ribosomes of a bacterium and have antibacterial activity against bacterial species close to or distant from the bacteriocin-synthesising bacterium. Bacteriocins have a high number of beneficial properties that make them of particular interest in various fields. LAB bacteriocins are more stable at the high temperatures and exhibit higher activity rate over a wide pH range. These antimicrobial peptides are also colourless, odourless and tasteless, which further increases their potential applications. Bacteriocins can now be used not only for food preservation, but also as promising antimicrobial compounds for therapeutic purposes, veterinary and cosmetological applications. The aim of this thesis was to characterise the new bacteriocin geobacillin 6 (Geo6). The bacteriocin geobacillin 6, encoded by the geo6 gene cluster, with a molecular mass of 5.5 kDa, was synthesised by heterologous biosynthesis in E. coli cells and purified by protein chromatography methods. The results showed that Geo6 bacteriocin remains stable at all tested temperatures, 60°C, 80°C, 100°C, and that from pH 4 to pH 6 in acidic media the activity of Geo6 bacteriocin is maximal and remains unchanged at 100 % compared to the control. Furthermore, it can be assumed that Geo6 has the highest stability at acidic pH, whereas it decreases at alkaline pH. The spatial structure of the protein has been evaluated and it is found that 90% of the protein is in an α-helical structure. Also, in comparison with the results of a previous study (Master's thesis of Anna K.), which showed that Geo6 bacteriocin acts only on some bacteria of the same genus. In the present study it was showed that Geo6 also acts on a thermophilic bacterium of a different genus, Aeribacillus pallidus - DSM 3670T, and on some mesophilic bacteria - Bacillus zanthoxyli CH07. |
