Title Utjecaj temperature na kinetiku rasta E. coli u mlijeku i jogurtu Title (english) The influence of temperature on the growth
kinetics of E. coli in milk and yogurt Author Chiara Košuta Mentor Mateja Ožanič (mentor)Committee member Ivana Gobin (predsjednik povjerenstva)Committee member Marina Šantić (član povjerenstva)Committee member Mateja Ožanič (član povjerenstva)Granter University of Rijeka Defense date and country 2020-09-15, Croatia Scientific / art field, BIOMEDICINE AND HEALTHCARE Abstract Escherichia coli je gram negativni ,oksidaza negativni ,katalaza pozitivni fakultativno anaerobni bacil. Poznato je da neki sojevi E. coli čine dominantni dio crijevne mikroflore čovjeka te doprinose normalnoj fiziologiji probavnog sustava. S druge strane neki sojevi E. coli uzrokuju infekcije probavnog te mokraćnog sustava. Najčešći sojevi E. coli koji uzrokuju infekcije probavnog sustava su Enterotoksična E. coli ,Enteropatogena E. coli , Enteroinvazivna E. coli te Enterohemoragična E. coli , dok je Uropatogena E. coli najčešći uzročnik infekcija mokraćnog sustava. E. coli se smatra mezofilnom bakterijom te joj za rast i razmnožavanje pogoduju temperature 20-40 °C. Prethodna istraživanja su dokazala da se E. coli uspješno razmnožava na temperaturama manjim od 30 °C te da u prirodi može dulje preživjeti na nižim nego na višim temperaturama u odnosu na optimalnu temperaturu rasta. Također su prethodna istraživanja dokazala da nekim sojevima E. coli za razmnožavanje više odgovaraju fluktuirajuće od stalnih temperatura. Cilj ovog završnog rada bio je ispitati utjecaj temperature na kinetiku rasta E. coli u uzorcima mlijeka i tekućeg jogurta. Kinetika rasta E. coli ispitivana je pri tri različite temperature ( 4 °C , 25 °C , 37 °C ) tijekom razdoblja od deset dana. Broj bakterija u uzorcima mlijeka i tekućeg jogurta praćen je u vremenskim razdobljima od 0, 3, 5, 7 i 10 dana od inokulacije. TBX agar je podloga koja je korištena za određivanje broja bakterija. Bakterijske suspenzije su neposredno prije nasađivanja na TBX agar deseterostruko razrijeđene te potom su agari inkubirani na 37 °C tijekom 24 sata te je nakon navedenog razdoblja očitan broj bakterija. Rezultati ovog istraživanja pokazuju da se E. coli u mlijeku razmnožava pri 4 °C , 25 °C te 37 °C, dok se u jogurtu E. coli razmnožava pri temperaturi od 25 °C i 37 °C, a pri temperaturi od 4 °C E. coli nema sposobnost razmnožavanja. Također dokazano je da se E. coli bolje razmnožava u mlijeku te da se pri temperaturi od 25 °C bakterije najbolje razmnožavaju.
Abstract (english) Escherichia coli is gram negative, oxidase negative, catalase positive optional anaerobic bacillus. It is known that some strains of E. coli form a dominant part of the human intestinal microflora and contribute to the normal physiology of the digestive system. On the other hand, some strains of E. coli cause infections of the digestive and urinary systems. The most common strains of. E. coli that cause gastrointestinal infections are Enterotoxic E. coli ,Enteropathogenic E. coli , Enteroinvasive E. coli, and Enterohemorrhagic E. coli , while Uropathogenic E. coli is the most common cause of urinary tract infections. E. coli is considered a mesophilic bacterium and temperatures of 20-40 °C are favorable for its growth and reproduction. Previous research has shown that E. coli reproduces successfully at temperatures below 30 °C and that it can survive longer in nature at lower than at higher temperatures in relation to the optimal growth temperature. Also, previous research has shown that some strains of E. coli are more suitable for reproduction fluctuating than constant temperatures. The purpose of this final work is to examine the influence of temperature on the growth kinetics of E. coli in samples of milk and l yogurt. The growth kinetics of E. coli were examined at three different temperatures (4 °C, 25 °C, 37 °C) during a period of ten days. The number of bacteria in milk and yogurt samples was monitored at 0, 3, 5, 7, and 10 days after inoculation. TBX agar is used to determine the number of bacteria. Bacterial suspensions were diluted tenfold immediately prior to inoculation on TBX agar, and then the agars were incubated at 37 °C for 24 hours, after which time the number of bacteria was read. The results of this study show that E. coli grows in milk at 4 °C, 25 °C and 37 °C, while E. coli grows in yogurt at a temperature of 25 °C and 37 °C, and E. coli does not have the ability to reproduce at a temperature of 4 °C. It has also been shown that E. coli reproduces better in milk and that bacteria grows the best at 25 °C.
Keywords
E. coli
mlijeko
tekući jogurt
kinetika rasta
temperatura
Keywords (english)
E. coli
milk
yogurt
the growth kinetics
temperature
Language croatian URN:NBN urn:nbn:hr:184:706677 Study programme Title: Study of Sanitary Engineering Type of resource Text File origin Born digital Access conditions Open access Terms of use Created on 2021-01-11 10:23:28
