Izolacija i identifikacija bakterija mliječne kiseline kao potencijalnih starter kultura

master's thesis

• Title (english): Isolation and identification of lactic acid bacteria as potentail starter cultures
• Author: Kristina Lacman
• 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: 2010-02, 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 su definirani kao 11 mezofilnih homofermentativnih koka te 3 termofilna heterofermentativna laktobacila. SDS-PAGE elektroforezom staničnih proteina, te RAPD (Randomly Amplified Polymorphic DNA) i PFGE (Pulsed Field Gel Electrophoresis) metodama je utvrđeno da se radi o 2 različita bakterijska soja koji su fenotipskom identifikacijom API testom definirani kao Enterococcus faecium i Lactobacillus fermentum što je potvrđeno i DNA fingerprinting metodom AFLP (Amplified Fragment Lenght Polymorphison). Izolirani bakterijski sojevi su nakon prekonoćnog uzgoja u obranom mlijeku proizveli cca 8,34 g/l mliječne kiseline i spustili pH vrijednost podloge za cca 2 pH jedinice. Ustanovljena je proteolitička aktivnost izoliranih sojeva kao jedno od važnih funkcionalnih svojstava starter kultura za fermentirane mliječne proizvode. Oba bakterijska soja su pokazala antimikrobno djelovanje prema šest različitih test – mikroorganizama što je također važno funkcionalno svojstvo starter kultura. 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 što je važno s tehnološkog aspekta priprave i čuvanja starter kultura.

Abstract (english)

15 Gram-positive, catalase-negative and non-sporogenic bacterial strains have been isolated from traditional fresh cheese. Isolated strains of lactic acid bacteria have been defined as 11 mesophilic homofermentative cocci and 3 termophilic heterofermentative lactobacili. Between 15 strains, 2 different strains have been distinguished by SDS-PAGE electrophoresis of cell proteins and with RAPD (Randomly Amplified Polymorphic DNA) and PFGE (Pulsed Field Gel Electrophoresis) methods. Phenotip analysis of these 2 strains by API test have revealed that these strains are Enterococcus faecium and Lactobacillus fermentum what has also been confirmed with DNA fingerprinting AFLP (Amplified Fragment Lenght Polymorphison) method. Isolated strains have produced cca 8.34 g/l of lactic acid after overnight growth in skim milk and pH value of the growth media was reduced by 2 pH units. Proteolytic activity have been established for both isolated strains, as important functional property of starter culture for the production of fermented milk products. Both strains have shown antimicrobial activity against six different test microorganisms what is also important functional aspect. 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 what is very important technological aspect.

• Keywords: svježi sir; probiotičke starter kulture; SDS-PAGE; RAPD; API; liofilizacija
• Keywords (english): fresh cheese; starter cultures; SDS-PAGE; RAPD; PFGE; API; freeze-drying
• Language: croatian
• URN:NBN: urn:nbn:hr:159:706062
• 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: 2017-08-28 11:47:07