| Abstract | U ovom je diplomskom radu istražen utjecaj enterocina bakterije Enterococcus faecalis EF- 101 na mikrofloru mljevenoga mesa pohranjenog u aerobnim uvjetima u hladnjaku na 4 °C. Enterocin je polu-pročišćen iz neutraliziranog nadtaloga (pH = 7; 10 N NaOH) kulture E. faecalis EF-101 precipitacijom amonijevim sulfatom (484.54 g/L). Aktivnost enterocina (AU/mL) testirana je prema indikatorskoj bakteriji Listeria monocytogenes NCTC 10527 i potom je dodano određeno razrjeđenje enterocina u fosfatnom puferu (pH = 7) u mljeveno meso (2560 AU/kg). Mljeveno meso s enterocinom i bez njega je mikrobiološki pretraživano u triplikatu tijekom četiri dana pohrane na broj aerobnih mezofilnih bakterija, enterobakterija, psihrotrofnih bakterija, stafilokoka, koliformnih bakterija, Escherichia coli, bakterija mliječne kiseline, L. monocytogenes te pH vrijednost. Ukupni broj bakterija, enterobakterija, psihrofila, stafilokoka, koliformnih i bakterija mliječne kiseline se povećavao očekivano tijekom pohrane, dok se pH nije znatno mijenjao. Antimikrobni učinak enterocina moguć je razlog smanjenja broja bakterija mliječne kiseline i enterobakterija na kraju pohrane za 0,3 odnosno 0,6 log. Enterocin je djelovao na psihrofile, koliforme i aerobne mezofilne bakterije nultoga dana tj. neposredno nakon njegovog dodavanja. Ostvareni rezultati upućuju na aktivnost enterocina u mesnom supstratu, no uz ograničeno antimikrobno djelovanje vjerojatno zbog njegove brze razgradnje tkivnim ili bakterijskim proteazama. Potrebno je dalje istražiti stabilnost i aktivnost enterocina EF-101 u kombinaciji s različitim antimikrobnim tehnologijama. |
| Abstract (english) | In this work the antibacterial effect of enterocin EF-101 was investigated in minced meat packed in aerobic conditions and cold-stored during the shelf-life. Enterocin was semi-purified from the neutralized supernatant (pH = 7; 10 N NaOH) of Enterococcus faecalis EF-101 by precipitation with ammonium sulphate (484.54 g/L). Activity of enterocin (AU/mL) was tested toward Listeria monocytogenes NCTC 10527 and appropriate solution of enterocin in phosphate buffer (pH = 7) was added to minced meat (2560 AU/kg). Minced meat with and without enterocin was microbiologicaly analysed on day 0, 1, 2, 3 and 4 in triplicate for the aerobic mesophilic bacteria count, enterobacteria, psychrophiles, staphylococci, coliforms, Escherichia coli, lactic acid bacteria, L monocytogenes and pH values. The number of aerobic mesophilic bacteria, enterobacteria, psychrophiles, staphylococci, coliforms and lactic acid bacteria increased during the storage in both groups, while pH was not significantly changed. However, an antimicrobial effect of enterocin may be the reason of 0.3 and 0.6 logs lower population of lactic acid bacteria and enterobacteria at the end of storage, respectively. Stil, the strongest antimicrobial effect was noted on the day 0, or immediately after the addition of enterocin, to the population of psychrophiles, coliforms and aerobic mesophilic bacteria. The obtained results indicate the activity of enterocin in the meat substrate, but with a limited antimicrobial effect probably due to it's rapid degradation by tissue or bacterial enzymes. It is necessary to further evaluate the stability and activity of enterocin EF-101 in the combination with other antimicrobial technologies. |
