Karakterizacija mikrobne populacije bakterija mliječne kiseline iz autohtonih sireva

master's thesis

• Title (english): Characterization of the lactic acid bacteria microbial population from autochthonous cheeses
• Author: Jelena Pobrić
• Mentor: Blaženka Kos (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Biochemical Engineering); (Laboratory for Antibiotic, Enzyme, Probiotic and Starter Cultures Technology); Zagreb
• Defense date and country: 2011-09-30, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Biotechnology

Abstract

U ovom radu provedena je izolacija i karakterizacija autohtone populacije bakterija mliječne kiseline (BMK), prirodno prisutne u tradicionalnom proizvedenom svježem siru, s ciljem definiranja probiotičkih starter kultura. Odabrane autohtone bakterije su pomoću klasičnih mikrobioloških metoda okarakterizirane kao gram-pozitivni, katalaza-negativni, nesporogeni, koki ili štapići, koji uspješno spuštaju pH vrijednost hranjive podloge, te sintetiziraju visoke koncentracije mliječne kiseline. Mikrobiološka analiza pokazala je da BMK predstavljaju dominantnu autohtonu bakterijsku populaciju u svježem siru. Iz autohtonog svježeg sira odabrano je 14 različitih bakterijskih sojeva, čija je daljna identifikacija, provedena sekvencioniranjem 16S rRNA gena, potvrdila da se radi o različitim sojevima BMK. Autohtoni izolati BGAL 3-19, BGAL 3-43, BGAL 3-54 i BGGO 5-3 su pokazali visoki stupanj preživljavanja u gastrointestinalnom traktu (GIT) in vitro. Odabrani izolat BGAL 3-19 je osjetljiv na sve ispitane antibiotike, osim na vankomicin, za koji predstavnici Lactobacillus vrsta imaju urođenu rezistenciju, dok je BGGO 5-3 pored vankomicina rezistentan i na neomicin i streptomicin. Analizom površinskih proteina autohtonih BMK pomoću SDS-PAGE utvrđeno je da soj BGGO 7-28 posjeduje S-layer protein koji može imati važnu ulogu u probiotičkim svojstvima ovog soja.

Abstract (english)

Isolation and characterization of the autochthonous lactic acid bacteria (LAB) population, naturally present in traditionally produced fresh cheese, was carried out, with an aim to define probiotic starter cultures. Selected autochthonous bacterial isolates were characterized as gram-positive, catalase-negative, asporogenous cocci or rods by conventional microbiological methods which are successfully in lowering the pH value of the medium and in synthesises of the high concentrations of lactic acid. Microbiological analysis revealed that LAB represent dominant autochthonous bacterial population in the fresh cheese. 14 different bacterial strains were selected from the autochthonous fresh cheese and their further identification by sequencing of the 16S rRNA gene confirmed that these are different LAB strains. Autochthonous isolates BGAL 3-19, BGAL 3-43, BGAL 3-54 and BGGO 5-3 showed high survival rates when exposed to the GIT in vitro. Selected isolate BGAL 3-19 is susceptible to the all tested antibiotics excluding vancomycin, for which the representatives of the Lactobacillus species have an innate resistance, while the BGGO 5-3 isolate is resistant even to neomycin and streptomycin. The analysis of the surface cell proteins of the autochthonous LAB by SDS-PAGE revealed the presence of the S-layer protein in BGGO7-28. This protein could be of importance in the probiotic properties of this particular strain.

• Keywords: autohtoni svježi sir; bakterije mliječne kiseline; identifikacija sekvencioniranjem 16S rRNA gena; probiotičke starter kulture
• Keywords (english): autochthonous fresh cheese; lactic acid bacteria; identification by sequencing 16S rRNA gene; probiotic starter cultures
• Language: croatian
• URN:NBN: urn:nbn:hr:159:343756
• Study programme: Title: Biotechnology; specializations in: Biochemical-Microbiology; Course: Biochemical-Microbiology; Study programme type: university; Study level: graduate; Academic / professional title: diplomirani inženjer biotehnologije; smjer biokemijsko-mikrobiološki (diplomirani inženjer biotehnologije; smjer biokemijsko-mikrobiološki)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-05-31 11:21:56