Isolation and Identification of Xerophilic Fungi from Various Dried Foods
Project no. 578 · Status: Kapanmış · 2016
Summary
One of the biggest problems of today's agriculture and food production is the deterioration caused by microbial contamination. Fungi that cause spoilage can grow under many extreme environmental conditions (ph, temperature, water activity, osmatic pressure). In order for microorganisms to perform vital functions, they must have access to free water. As the amount of solute (salt, sugar, glycerol etc.) or ion increases, the amount of free water in the environment decreases. Many microorganisms causing food contamination continue their lives thanks to the free water in the environment. Water activity is expressed in values ranging from 0.0 to 1.0. The water activity of distilled water, which does not contain various sugars and other soluble substances, is 1.0. The aw value of a completely dry food-free food is 0.0. Most microorganisms cannot survive at a water activity value below 0.85 aW. But there are microorganisms called xerophilic that can survive in low water activities. Since many dried foods are low in water activity, most microorganisms cannot thrive in this environment. There are fungi that can adapt to this harsh environment, such as dried foods. These fungi also threaten human health by producing various mycotoxins The aim of this study is to isolate xerophilic fungi from dried foods with low water activity and to identify them with molecular biological methods. Isolations were made using selective media with low water activity (DG18 and malt extract agar with 60% glucose). As an example of xerophilic fungus isolation, foods with low water activity such as chocolate, dried fish, noodles, dried grapes and bread were used. After macroscopic examination of the purified fungus isolates, they were identified at the genus and species level using one of the molecular biological methods, the ITS (Internal transcribed spacer) gene region. As a result, 18 fungi species were detected. The minimum water activity values that these fungus species can reproduce were also tested. As a result of the study, Aspergillus, Wickerhamomyces, Debaryomyces, Cladosporium, Pichia, Zygosaccharomyces, Penicillium genus were obtained. All species were evaluated as saccharophilic, since all the species that have been identified can grow at a high glucose rate (60%) where most microorganisms cannot survive. It is dangerous because the isolated species can produce various mycotoxins that threaten food and human health. Therefore, microorganism (bacteria, fungus) screening in dried foods is recommended with this study.