Karakterizacija sojeva bakterija mliječne kiseline izoliranih iz tradicionalnog svježeg sira

master's thesis

• Title (english): Characterization of the lactic acid bacterial strains isolated from tradicional cottage cheese
• Author: Marina Štimac
• Mentor: Jagoda Šušković (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: 2008-12, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Biotechnology

Abstract

Iz uzorka tradicionalnog svježeg sira je izolirano 15 gram-pozitivnih, katalaza-negativnih i nesporogenih bakterijskih sojeva. Izolirani sojevi bakterija mliječne kiseline je definirano kao 11 mezofilnih laktokoka te 3 termofilna laktobacila. SDS-PAGE elektroforezom ukupnih staničnih proteina i RAPD metodom je utvrđeno da se radi o 4 različita bakterijska soja koji su fenotipskom identifikacijom API testom definirani kao Lactococcus lactis, Lactobacillus plantarum, Lactobacillus brevis i Lactobacillus paracasei. Izolirani bakterijski sojevi pokazuju proteolitičko djelovanje, antimikrobno djelovanje prema šest različitih test – mikroorganizama te dodatno bakteriocinsko djelovanje prema srodnim bakterijskim vrstama. Izolirani bakterijski sojevi pokazuju dobru podnošljivost prema visokoj koncentraciji vodikovih iona (pH = 2,0) i djelovanju pepsina u simuliranom sekretu želuca. Neosjetljivi su prema djelovanju enzima gušterače i pokazuju otpornost prema djelovanju žučnih soli (3,0 mg/ml). Izolirani laktokoki su osjetljivi na sve ispitane antibiotike, dok su laktobacili rezistentni na vankomicin. Bakterijski sojevi su preživjeli proces liofilizacije u visokom broju (cca 109 CFU/ml), a broj živih stanica liofiliziranih bakterijskih kultura ostao je nepromijenjen tijekom tri mjeseca čuvanja.

Abstract (english)

15 Gram-positive, catalase-negative and non-sporogenic bacterial strains have been isolated from traditional cottage cheese. Isolated strains of lactic acid bacteria have been defined as 11 mesophilic lactococci and 3 termophilic lactobacili. Between 15 strains, we have distinguished 4 different strains by SDS-PAGE electrophoresis of whole cell proteins and RAPD method. Phenotip analysis of these 4 strains by API test have revealed that these strains are Lactococcus lactic, Lactobacillus plantarum, Lactobacillus brevis i Lactobacillus paracasei. Isolated strains have shown proteolitic activity, antimicrobial activity against six different test microorganisms, and potentially bactericine activity against similar bacterial species. Isolated bacterial have shown good tolerance to high concentration of hydrogen ions (pH = 2.0) and pepsin action in simulated stomach secrete. They were insensitive against the action of pancreatic enzymes and have shown resistance against the activity of bile acids (3,0 mg/ml). All tested antibiotics are inhibitory against isolated lactococci, while lactobacili have shown resistance to vancomycine. Isolated bacterial strains have survived the freeze-drying process successfuly (~109 CFU/ml) and the number of live cells stayed immutable during the three mounts of preservation.

• Keywords: svježi sir; probiotičke starter kulture; SDS-PAGE; RAPD; API
• Keywords (english): cottage cheese; probiotic starter cultures; SDS-PAGE; RAPD; API
• Language: croatian
• URN:NBN: urn:nbn:hr:159:457186
• Study programme: Title: Biotechnology; specializations in: Biochemical Engineering; Course: Biochemical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: diplomirani inženjer biotehnologije; smjer biokemijsko inženjerstvo (diplomirani inženjer biotehnologije; smjer biokemijsko inženjerstvo)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-08-31 10:58:34