Yöresel Ekşi Hamurlardan Saccharomyces Cerevisiae Suşlarının İzolasyonu, Tanımlanması ve Multifonksiyonel Özelliklerinin Belirlenerek Endüstriyel Öneme Sahip Suşların Saptanması

Abstract

In this thesis research, it was aimed to determine industrially important indigenous Saccharomyces cerevisiae strains isolated from local sourdoughs by examining strains’ multifunctional properties. For this purpose, 38 samples that were collected from various regions of Turkey where bread production was widely made by sourdough fermentation were examined. It was determined that total yeast counts in the sourdough samples varied between 3.5-7.1 log cfu/g. A total of 185 potential S. cerevisiae isolates were obtained from these samples by using WL Nutrient agar medium. So as to identify of these isolates, API ID 32C yeast identification system and some complementary tests were applied. According to obtained results, 146 out of 185 isolates were precisely identified as S. cerevisiae. Afterwards, total 83 strains were selected for analyses of determination of technological properties by assessing macroscopic morphologies on WL Nutrient agar medium, carbon assimilation profiles, and complementary tests’ results of examined strains. Strains’ growth features at different temperature, pH values, and different salt concentrations and their resistance to lactic and acetic acids and their leavening ability and their catalase, lipolytic, and proteolytic activities were examined. In addition to these, by using API-ZYM enzyme test kit, the enzyme profiles of tested strains were revealed. The results obtained from technological and enzymatic characterization experiments were evaluated statistically through the Principal Component Analysis (PCA). Twenty-three S. cerevisiae strains that were found out to be superior in terms of technological and enzymatic properties were selected for investigation of probiotic properties. Strains’ antibiotic resistance, antimicrobial activities, resistance to low pH and bile salt, hydrophobicity properties, and ability of biofilm production were examined. PCA was applied to the data obtained from the tests. As a result of statistical analysis, it was determined that seven S. cerevisiae (S. cerevisiae Kafes 2, Orencik 2-1, Orencik 5-1, Orencik 6-2, Odunpazarı 2, Carsa 1-6 and Gerede 2-3) out of 23 tested strains can be categorized as multifunctional strains and have importance in terms of industry thanks to having potential probiotic. In this thesis research, moreover, the fermentation capacity of 23 S. cerevisiae strains was also examined. It was found out that seven tested strains had better results than the commercial yeast used as control and others’ calculated fermentation rates were close to the control strain. Finally, in this research, DNA sequence analysis of 26 strains which have potential to be used as starter in food industry was realized and was molecularly confirmed. It was determined that all tested strains’ base length of ITS regions was approximately 800 bp. As a result of DNA sequence analysis, 23 strains were verified as S. cerevisiae, while 3 were verified as S. cerevisiae/S. paradoxus. In addition, it was understood that S. cerevisiae Manisa 3 and Carsa 1-6 strains could be the new S. cerevisiae strains because their ITS sequence similarities were lower than 95%.