Doğal Ekşi Hamurlardan Laktik Asit Bakterilerinin İzolasyonu ve Tanımlanması ile Bazı Probiyotik Özelliklerinin Saptanması

Abstract

The use of starters in bread making is an essential and important step. Commercial starters used for this purpose provide saving of time and breads have different properties as compared to conventional breads. Recently, presence of GMOs in additives has caused serious concerns especially in consumers and this situation has also affected bread producers. The aim of this thesis was to isolate lactic acid bacteria (LAB) from 7 different sourdough samples provided from bakeries located in various regions of our country and sourdoughs prepared within the scope of the project called “Isolation of Lactic Acid Bacteria and Yeasts from Natural Sourdoughs and Determination of Their Effects on Bread Making Quality” using 18 flour samples obtained from different mills both domestic and abroad. Firstly, 10 possible LAB isolates from collected sourdough samples and also 143 possible LAB isolates from the prepared sourdough samples were pre-identified by MALDI-TOF Mass Spectrometer. According to the data obtained from 7 dough samples collected, the identification of the species such as Lactobacillus sanfranciscensis in microflora increased the possibility that commercial culture was used in the dough. Therefore, instead of dough samples, sourdoughs prepared from the flour samples collected from different regions continued to work. 106 of the isolates could be identified by MALDI-TOF Mass Spectrometer. Among the pre-identified isolates, Lactobacillus plantarum (57) and Lactobacillus brevis (20) strains, which are the most commonly found in the sourdoughs and show better technological properties, were selected. 10 Lactobacillus plantarum and 7 Lactobacillus brevis isolates were selected by grouping as sample/microorganisms types. Molecular confirmation and then molecular identification of 17 isolates was made by Real-Time PCR and 16S rRNA sequence analysis, respectively. PCR results and 16S rRNA sequence analysis showed 100% harmony with each other. In addition, some probiotic properties (acid tolerance and bile tolerance) of the isolates were researched. 17 isolates showed statistically significant differences in terms of acid and bile tolerance (p <0.01). Among the isolates, Lactobacillus plantarum isolate coded as Wz3 was found to be the most resistant to acid application, while Ç4-coded Lactobacillus plantarum was determined as the most vulnerable isolate. In terms of bile tolerance, the A1-coded Lactobacillus brevis isolate was the most resistant, while the TB6 / 4-coded Lactobacillus plantarum was identified as the most susceptible isolate. In addition, all isolates showed resistance to both bile and acid applications and they were able to survive. Since these isolates are obtained from the doughs prepared from the collected flours, it can be concluded that they are less likely to be commercial cultures and have superior probiotic properties as compared to the commercial preparates. In the light of analyzes, it was determined that 17 isolates had the potential to be used as starter in sourdough and also showed similar properties to probiotic bacteria in terms of resistant to the bile and acids. It is expected that 17 strains obtained from this study will be based on the studies that will be carried out in order to evaluate their breadmaking quality as an alternative culture in bakery.