Fermentacija i antimikrobna aktivnost vodenih kefirnih zrnaca

undergraduate thesis

• Title (english): Fermentation and antimicrobial activity of water kefir grains
• Author: Petra Grünfeld
• Mentor: Sunčica Beluhan (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Biochemical Engineering); (Laboratory for Biochemical Engineering, Industrial Microbiology and Malting and Brewing Technology); Zagreb
• Defense date and country: 2019-06-14, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Biotechnology

Abstract

Vodeni kefir je blago kiselo, alkoholno i voćno fermentirano piće, čija fermentacija započinje s vodenim kefirnim zrncima. Vodena kefirna zrnca sastoje se od polisaharida i sadrže mikroorganizme potrebne za fermentaciju vodenog kefira. U ovom radu, proces fermentacije vodenog kefira proveden je tijekom 12 dana kako bi se otkrila dinamika združene kulture bakterija mliječne kiseline (rod Lactobacillus), octene kiseline (rod Acetobacter) i kvasaca (vrste Saccharomyces cerevisae i Dekkera bruxellensis), kao i kinetika potrošnje supstrata i proizvodnje metabolita. Glavni supstrat, saharoza, je u potpunosti metaboliziran nakon 4 dana fermentacije, što se podudara s proizvodnjom većeg dijela polisaharida vodenih kefirnih zrnaca. Glavni metaboliti fermentacije bili su mliječna i glukonska kiselina. Octena kiselina i etanol proizvedeni su u niskim koncentracijama. Najveći dio ovih metabolita nastao je tijekom prvih 96 sati fermentacije, pri čemu se pH smanjio s 3,86 na 3,45. Antimikrobna aktivnost je testirana na bakterijama vrsteEscherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium te kvascu vrste Candida albicans. Uočena je izvrsna antimikrobna aktivnost na bakterije i kvasac, no ne i na bakteriju vrste E. coli.

Abstract (english)

Water kefir is mild sour, alcoholic, and fruity fermented beverage, of which the fermentation is started with water kefir grains. The water kefir grains consists of polysaccharides and microorganisms responsable for the water kefir fermentation. In this work, a water kefir fermentation process was followed during 12 days to unravel the symbiotic community dynamics of lactic acid bacteria (genus Lactobacillus), acetic acid bacteria (genus Acetobacter), and yeasts (species Saccharomyces cerevisiae and Dekkera bruxellensts), as well as the kinetics of of substrate consumption and metabolite production.The major substrate, sucrose, was complitely converted after 4 days of fermentation, which coincided with the production of the major part of the water kefir grain polysaccharide. The main metabolites of the fermentation were lactic and gluconic acid. Acetic acid and ethanol were produced at minor concentrations. The major part of these metabolites was produced during the 96 h of the fermentation, during which the pH decreased from 3.86 to 3.45. The antimicrobial activity was tested against bacteria Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, as well as yeast Candida albicans. Antimicrobial activities were observed in the fermented samples against the investigated bacteria strains and C. albicansbut E. coli was not inhibited.

• Keywords: vodeni kefir; organske kiseline; antmikrobna aktivnost
• Keywords (english): water kefir; organic acids; antimicrobial activity
• Language: croatian
• URN:NBN: urn:nbn:hr:159:577685
• Study programme: Title: Biotechnology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka biotehnologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka biotehnologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2019-07-12 08:53:48