Bütünleşik Omik Yaklaşımı ile Geleneksel Tarhana Fermantasyonu Mikrobiyomunun Araştırılması

Abstract

Tarhana is a traditional product prepared by mixing cereals, dairy products, various vegetables, and spices, followed by the lactic and alcoholic fermentation of the resulting dough. Commercially or mostly in households, traditional ingredients varying by region, along with fermentation, drying, and grinding stages, result in tarhana with specific characteristics depending on the recipe. In this study, 19 different samples obtained during the fermentation process of tarhana doughs prepared with recipes from the provinces of Isparta, Maraş, Bursa, Kastamonu, and Uşak were evaluated for their microbiota and relationships between metabolites using chemical, microbiological, metagenomic, and metabolomic analyses. Chemical analyses determined pH, total acidity, total fat, protein, ash, and dry matter amounts for the tarhana varieties under investigation, ensuring the correct progression of the tarhana fermentation process. Microbiological analyses, conducted using classical cultural methods, identified microbial loads during fermentation processes, and pure cultures were isolated. The isolated pure cultures were identified using Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF) technology. Additionally, high-throughput sequencing analyses revealed the bacterial and fungal microbiota of the samples. The amounts of lactic, succinic, acetic, citric, pyruvic, uric, oxalic, and formic acids in tarhana doughs during the fermentation process were detected using a high-performance liquid chromatography device (HPLC) with a Diode Array Detector (DAD) and an InertSustain AQ-C18 column (3 µM, 4.0x 150 mm (UP)). The change in ethanol content in tarhana doughs during fermentation was determined by gas chromatography (GC) using a DB-624, 30m x 0.53mm column with a Flame Ionization Detector (FID). To reveal the distribution based on tarhana type and production differences, relationships between the microbiota and metabolites of all tarhana samples were evaluated using principal component analyses, heatmaps, and correlation analyses. Bursa variety had the highest pH values at the beginning (pH 5.41) and end (pH 4.72) of fermentation, while Kastamonu tarhana had the lowest initial (pH 4.02) and final (pH 3.86) pH values. Metagenomic analyses indicated the highest relative abundance of Pediococcus acidilactici in Bursa tarhana, Lactiplantibacillus plantarum in Kastamonu tarhana, Levilactobacillus namurensis, and Levilactobacillus zymae in Uşak tarhana. In the fungal microbiota, Kluyveromyces in Isparta and Maraş varieties, Saccharomyces in Bursa tarhana, and Issatchenkia in Kastamonu variety were found to have the highest relative abundance. Uşak tarhana contained higher amounts of lactic, succinic, and acetic acids compared to other varieties, with these three organic acids being major organic acids for all varieties, respectively. Integrated analyses also demonstrated that tarhana varieties formed distinct clusters based on the type and production process differences. In this study, the biocultural fingerprints of Isparta, Maraş, Bursa, Kastamonu, and Uşak tarhana varieties were revealed both microbiologically and metabolically, depending on fermentation time and tarhana type. Statistical comparisons at the end of the study identified unique qualitative and quantitative characteristics for each type of tarhana based on fermentation time, utilizing integrated omic technologies.