Izolacija i karakterizacija proteolitičkih sojeva bakterija i kvasaca iz ovčjeg i kozjeg sira

master's thesis

• Title (english): Isolation and characterization of proteolytic bacteria and yeast strains from sheep and goat cheeses
• Author: Dragana Zadro
• Mentor: Vladimir Mrša (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Chemistry and Biochemistry); (Laboratory for Biochemistry); Zagreb
• Defense date and country: 2016-09-26, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology

Abstract

Cilj ovog rada bila je izolacija i karakterizacija mikroorganizama iz ovčjeg i kozjeg feta sira. Provedena je selektivna izolacija i prebrojavanje kvasaca i bakterija te izolacija pojedinačnih kolonija i njihova karakterizacija na WL hranjivoj podlozi. Ukupno je izolirano 17 kolonija, od toga 4 kvasca s površine ovčjeg sira i 13 bakterija s površine i unutarnjih dijelova obje vrste sira. Provedena je karakterizacija izoliranih spojeva promatranjem morfologije stanica i kolonija, rasta na različitim temperaturama, bojanja po Gramu i provedbom katalaza, oksidaza i ureaza testa. Proteolitička aktivnost nije detektirana u slučaju izoliranih sojeva kvasca, dok su bakterijski izolati pokazali značajnu proteolitičku aktivnosti detektiranu na SM agar podlozi. Nadalje, testiranjem proteolitičke aktivnosti u različitim medijima, pokazalo se da određene komponente hranjivog medija, poput peptona i natrijevog klorida mogu utjecati na proteolitičku aktivnost izoliranih sojeva. Spektrofotometrijskim mjerenjem aktivnosti sojeva pri različitim temperaturama, pH vrijednostima i načinima uzgoja, soj G-2b je pokazao najveću aktivnost pri pH 9, 25°C i uzgojem na tresilici.

Abstract (english)

Aim of this work was to isolate and characterize microorganisms from two types of Feta cheese made from sheep and goat milk. Selective isolation and enumeration of yeasts and bacteria were performed, which was followed by obtaining and characterizing single colonies on WL nutrient medium. Altogether 17 colonies were isolated, 4 yeasts from surface of sheep cheese, and 13 bacteria from surface and inside parts of both cheeses. Isolated strains were characterized by observing their cell and colony morphology, growth at different temperatures, Gram staining, and catalase, oxidase and urease tests. Proteolytic activity was not detected in case of yeast strains, while bacterial isolates showed considerable proteolytic activity detected on SM agar. Furthermore, testing the proteolytic activity in different media, it has been shown that certain components of growth media, like peptone and sodium chloride, could affect ability of bacterial strains to produce proteolytic enzymes. Quantifying the proteolytic activity with spectrophotometric measurements at different temperatures, pH values and way of culturing, strain G-2b showed the highest activity at pH 9 and 25°C in agitating cultivation conditions.

• Keywords: proteaze; izolacija; bakterije; kvasci; karakterizacija; proteoltička aktivnost
• Keywords (english): proteases; isolation; bacteria; yeasts; characterization; proteolytic activity
• Language: croatian
• URN:NBN: urn:nbn:hr:159:664242
• Study programme: Title: Food Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka prehrambenog inženjerstva (magistar/magistra inženjer/inženjerka prehrambenog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-04-25 10:53:03