Funkcionalni i tehnološki aspekti pri odabiru probiotičkih starter kultura

master's thesis

• Title (english): Functional and technological aspects in the autochthonous lactic acid bacteria selection
• Author: Dana Mrvić
• 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: 2011-07-15, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Biotechnology

Abstract

U ovom radu provedena je izolacija autohtono prisutnih bakterija mliječne kiseline (BMK), iz tradicionalno proizvedenog kiselog kupusa, a osobit je naglasak stavljen na tehnološke karateristike odabranih sojeva s ciljem definiranja probiotičkih starter kultura. Primjenom klasičnih mikrobioloških metoda i SDS-PAGE elektroforeze ukupnih stanicnih proteina, te API 50 CHL testa odabrani autohtoni bakterijski izolati identificirani su kao BMK. Provedena su istraživanja njihovih funkcionalnih svojstava, prije svega preživljavanje u gastrointestinalnom traktu (GIT) koje je najvažniji kriterij pri izboru probiotika. Autohtoni izolati SF1, SF2, SF4, SF9 i SF13 su pokazali visoki stupanj preživljavanja u GI in vitro uvjetima. RAPD analizom DNA profila, dobivenih sa specifičnom oligonukleotidnom početnicom, potvrđeno je da se radi o različitim sojevima BMK. Odabrani izolati su osjetljivi na ispitane antibiotike, osim na vankomicin. Isti sojevi su ispunili važne selekcijske kriterije za probiotike: antimikrobno djelovanje, sposobnost autoagregacije i koagregacije s potencijalnim kontaminantima hrane. Sve odabrane autohtone BMK nakon prekonoćnog uzgoja u MRS hranjivoj podlozi uspješno spuštaju pH vrijednosti ispod 4,44. Većina izolata nije osjetljiva na inhibicijsko djelovanje nisina u koncentraciji 75 μg/l, dok visoke koncentracije NaCl (6.0%) najuspješnije toleriraju SF2, SF9 i SF13. Liofilizacijom su pripremljeni suhi aktivni preparati odabranih bakterijskih sojeva. Nakon liofilizacije broj živih stanica primjenjenih kultura se održao visok (cca 109 CFU/ml), što je važno svojstvo s tehnološkog aspekta priprave, čuvanja i primjene sojeva u industrijskom mjerilu.

Abstract (english)

In this thesis an isolation of autochthonous lactic acid bacteria (LAB) from traditionally made sauerkraut, with a special focus on their technological characteristics, was performed. Classical microbiological methods, SDS-PAGE of whole cell proteins and API sugar fermentation profiles revealed that all autochthonous isolates were LAB. The most important functional property of probiotics, survival in gastrointestinal tract conditions was investigated. According to the results, autochthonous LAB SF1, SF2, SF4, SF9 and SF13 have shown the highest survival rates in GI conditions in vitro, which were identified as different LAB strains by RAPD analysis with specific primers. Tested strains revealed as sensitive to the all tested antibiotics, but not to vancomycin. These strains express some important probiotic properties such as antimicrobial activity, autoaggregation and coaggregation with pathogens. Furthermore, after overnight growth, all tested strains lowered the pH value of the medium below 4.44. Autochthonous LAB were mostly inhibited by 75 μg/l of purified nisin, while strains SF2, SF9 and SF13 best tolerated the highest NaCl concentration (6.0% w/v). Isolated bacterial strains have successfully survived the freezedrying process (app 109 CFU/ml), what is important from technological aspect in the industrial production of starter cultures.

• Keywords: antimikrobno djelovanje; identifikacija bakterija; liofilizacija; probiotičke starter kulture; tolerancija na nisin
• Keywords (english): antimicrobial activity; bacterial identification; freeze-drying; probiotic starter cultures; tolerance to nisin
• Language: croatian
• URN:NBN: urn:nbn:hr:159:518036
• Study programme: Title: Nutrition; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra nutricionizma (magistar/magistra nutricionizma)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-05-31 11:17:44