Uporaba mlečnokislinskih in ocetnokislinskih bakterij za proizvodnjo brezalkoholnih fermentiranih pijač

The main goal of the master thesis was to evaluate the possibility to isolate new strains from complex microbial communities and their use in controlled fermentation processes to create novel alcohol free or low-alcohol beverages. The methods used were metagenomics for characterization of the microbial communities of water kefir and molecular identification of isolated colonies. Next steps were focused to characterize and compare the identified bacteria from water kefir to the commercially available lactic acid bacteria (LAB) and acetic acid bacteria (AAB). Further, some of the selected LAB and AAB strains were used for fermentation of (un)hopped wort to produce alcohol free and low-alcohol beverages. Low-alcohol beverages were created with sequential fermentations using non-maltose fermenting strains of Saccharomyces cerevisiae. To create more complex flavor of the products, apple juice was also fermented using strains of AAB and then blended with the fermented unhopped wort by LAB strains. The results showed that isolated water kefir strains were not better for wort fermentation than commercially available lyophilized strains and that the primary fermentation did not have a significant effect on the production of aroma compounds (e.g. esters) during secondary fermentation when sequential fermentations were performed. AAB isolated from water kefir had better sensory characteristic than the AAB strains from laboratory collection. The results showed that novel strains can be isolated from complex microbial communities and used in controlled fermentations processes for production of novel beverages.Namen magistrskega dela je bil raziskati možnost izolacije novih sevov iz kompleksne mikrobne združbe in jih uporabiti v nadzorovani fermentaciji za izdelavo novih brezalkoholnih in nizkoalkoholnih pijač. Uporabljene metode so bile metagenomika za karakterizacijo mikrobne združbe vodnega kefirja in molekularna identifikacija izoliranih kolonij. Naslednji koraki so bili usmerjeni v karakterizacijo in primerjavo izoliranih sevov iz vodnega kefirja s komercialno dostopnimi sevi mlečnokislinskih (MKB) in ocetnokislinskih bakterij (OKB). Nekatere izmed izbranih sevov MKB in OKB smo nadalje uporabili za fermentacijo sladice/pivine za proizvodnjo brezalkoholnih in nizkoalkoholnih pijač. Nizkoalkoholne pijače smo proizvedli z dvo-stopenjsko zaporedno fermentacijo, pri kateri smo uporabili kvasovko Saccharomyces cerevisiae, ki ne uporablja maltoze. Za pridobitev bolj kompleksnih okusov smo uporabili jabolčni sok, smo ga fermentirali z OKB in nato združili s fermentirano sladico. Rezultati so pokazali, da sevi MKB izolirani iz vodnega kefirja nimajo boljših lastnosti kot komercialno dostopni sevi in da primarna fermentacija pri zaporedni fermentaciji ni imela večjega vpliva na razvoj aromatičnih spojin (estrov) pri fermentaciji s kvasovko. Izolirani sev OKB iz vodnega kefirja je imel boljše lastnosti kot seva iz zbirke. Raziskovalna naloga je pokazala, da je mogoče izolirati nove seve iz kompleksnih mikrobnih združb in jih uporabiti v nadzorovani fermentaciji za proizvodnjo brezalkoholnih in nizkoalkoholnih pijač