MELİH GUNAY | Canakkale Onsekiz Mart University (original) (raw)

Papers by MELİH GUNAY

Muş Alparslan üniversitesi fen bilimleri dergisi, Dec 26, 2022

Kaktüs armut bitkisi (Opuntia ficus-indica (L.) Mill.) yetiştiği coğrafya ve iklim koşulları nede... more Kaktüs armut bitkisi (Opuntia ficus-indica (L.) Mill.) yetiştiği coğrafya ve iklim koşulları nedeniyle sıcaklığa ve kuraklığa toleransı oldukça yüksek olan bir kaktüs türüdür. Bu kaktüs türünün bozulmaya başlayan kladotları ve meyveleri mayaların ve diğer mikroorganizmaların çoğalabilmesi için uygun alan oluşturmaktadır. Maya hücreleri stres koşullarında stres metaboliti olarak trehaloz ve glikojen biriktirir. Çalışmamızda kaktüs armut meyvesinden stres dirençli maya türlerinin izole edilerek moleküler yöntemlerle tanımlanması ve depo karbonhidrat birikimlerinin belirlenmesi amaçlandı. Termotolerant ve osmotolerant maya suşlarının moleküler tanımlanmasında 26S rDNA-D1/D2 gen bölgesinin dizi analizi kullanıldı. Stres dirençli maya suşlarının trehaloz ve glikojen birikimleri stres koşullarında enzimatik olarak belirlendi. İzole edilen K. marxianus, K. lactis ve P. kudriavzevii maya türlerine ait tüm maya suşlarının termotolerant ve osmotolerant maya suşları olduğu gözlendi. K. marxianus ve K. lactis maya türünde stres metaboliti olarak glikojenin P. kudriavzevii maya türünde ise trehalozun tercih edildiği belirlendi. Diğer izole edilen A. pullulans, H. opuntiae ve P. kluyveri türlerine ait maya suşları arasında stres toleransının ve depo karbonhidratın stresin derecesine ve çeşidine bağlı olarak değiştiği tespit edildi. İzole edilen K. marxianus ve K. lactis maya suşlarının süt ürünleri endüstrisinde, P. kudriavzevii maya suşlarının ise biyoetanol ve fermentasyon endüstrisinde kullanımı için uygun potansiyele sahip oldukları değerlendirildi.

ß anakkale, Turkey Genc ß TT, Kaya S, G€ unay M, C ß akalo glu C ß. Humoral immune response of Ga... more ß anakkale, Turkey Genc ß TT, Kaya S, G€ unay M, C ß akalo glu C ß. Humoral immune response of Galleria mellonella after mono-and co-injection with Hypericum perforatum extract and Candida albicans. APMIS. 2024. Galleria mellonella is used as a model organism to study the innate immune response of insects. In this study, the humoral immune response was assessed by examining phenoloxidase activity, fungal burden, and the expression of phenoloxidase and antimicrobial peptide genes at different time point following separate and combined injections of Hypericum perforatum extract and a nonlethal dose of Candida albicans. The administration of a plant extract at low doses increased phenoloxidase activity, while higher doses had no effect. Similarly, co-injection of a low dose of the extract with the pathogen allowed half of the yeast cells to survive after 24 h. Co-injection of plant extract with the pathogen decreased the phenoloxidase activity at the end of 4 h compared to C. albicans mono-injection. The phenoloxidase gene expressions was reduced in all experimental conditions with respect to the control. When plant extracts and the pathogen were administered together, gallerimycin and hemolin gene expressions were considerably higher compared to mono-injections of plant extracts and the pathogen. The results of this study reveal that gene activation and regulatory mechanisms may change for each immune gene, and that recognition and signaling pathways may differ depending on the involved immunoregulator.

Scientific article, May 1, 2023

The determination of yeast microbiota in cheeses and the physiological properties of yeasts are v... more The determination of yeast microbiota in cheeses and the physiological properties of yeasts are very important for the dairy industry. In addition, the physiological features, proteolytic and lipolytic activities, and stress tolerance of yeasts have a significant role in the selection of starter yeast species for cheese ripening. This study aimed to determine industrially important yeasts isolated from cheese samples. Molecular techniques identified the isolated yeast strains. The yeast strains' extracellular enzyme activities, fermentation capacities, and thermotolerance and osmotolerance properties were also evaluated. A total of 81 yeast strains were isolated and characterized from three types of cheese sample s. PCR-RFLP determined the isolated yeast strains and sequence analysis of ITS1-5.8S-ITS2 and 26S rDNA regions. A maximum parsimony tree was constructed by MEGA X software to evaluate the phylogenetic relationship of identified yeast strains. Candida intermedia, Candida parapsilosis, Clavispora lusitaniae, Debaryomyces hansenii, Kluyveromyces marxianus, Pichia kudriavzevii, and Wickerhamomyces anomalus yeast species were identified on cheese samples. The distribution of identified yeast species on cheese samples was determined as 48.1% for W. anomalus, 17.3% for K. marxianus, 14.8% for C. parapsilosis, 8.6% for D. hansenii, 4.9% for Cl. lusitaniae, 3.7% for C. intermedia and 2.5% for P. kudriavzevii. The W. anomalus yeast species was common in three cheese types. All strains of W. anomalus and P. kudriavzevii yeast species, three C. parapsilosis, and two Cl. lusitaniae yeast strains have important physiological properties for industrial applications. These yeast strains have the potential to be used in combinat ion as starter cultures to improve cheese maturation in the future. This comprehensive study identifies yeast species by ITS1-5.8S-ITS2 and 26S rDNA regions and determines industrially important yeast species using multiple criteria (extracellular enzyme activity, stress tolerance, and fermentation capacity).

EJONS INTERNATIONAL JOURNAL ON MATHEMATICS, ENGINEERING & NATURAL SCIENCES, Sep 20, 2021

Saccharomyces cerevisiae maya hücreleri tarafından depo karbonhidratı trehaloz ve glikojen olarak... more Saccharomyces cerevisiae maya hücreleri tarafından depo karbonhidratı trehaloz ve glikojen olarak biriktirilir. Trehaloz ayrıca stres koruyucu özelliğe sahip olup ve maya hücrelerini fizyolojik streslerden korur. Maya hücreleri düşük besin içeren ortamdan zengin besin içeren ortama geçirildiğinde depo karbonhidratları hızlı bir şekilde glikoza parçalanır. Trehaloz biyosentezi TPS kompleksi tarafından ve trehaloz yıkımı nötral trehalaz enzimi tarafından katalizlenir. Glikojen sentezi glikojenin, glikojen sentaz ve dallanma enziminin aktiviteleri ile gerçekleştirilir. Glikojenin parçalanması ise glikojen fosforilaz ve glukoamilaz tarafından katalizlenir. Maya hücrelerinde TOR (Target of rapamisin) sinyal yolağı normal büyüme koşullarında farklı hücresel süreçleri ve sinyal yolaklarını aktive eder. Rapamisin ve kafein uygulamasına ilave olarak zayıf azot kaynağıda TOR sinyal yolunu inhibe eder. Bu araştırmada, TOR sinyal yolağının depo karbonhidrat metabolizması üzerindeki etkileri ?to...

International Journal on Mathematic, Engineering and Natural Sciences, 2021

Trehalose and glycogen are deposited by Saccharomyces cerevisiae yeast cells as storage carbohydr... more Trehalose and glycogen are deposited by Saccharomyces cerevisiae yeast cells as storage carbohydrates. Trehalose also serves as a stress protectant and protects yeast cells from physiological stresses. Reserve carbohydrates rapidly degraded to glucose when the yeast cells transferred from nutritionally poor to rich medium. The biosynthesis of trehalose is catalyzed by the TPS complex and the breakdown of trehalose is catalyzed by a neutral trehalase enzyme. The glycogen synthesis requires the activities of glycogenin, glycogen synthase and the branching enzyme. The breakdown of glycogen is catalyzed by glycogen phosphorylase and glucoamylase. TOR (Target of rapamycin) signalling pathway activates many cellular processes and signalling pathways under normal growth conditions in yeast. Besides rapamycin and caffeine treatment, a poor nitrogen source inhibits the TOR pathway. In this research, the effects of the TOR pathway on the reserve carbohydrate metabolism were investigated using Δtor1 mutant and its isogenic wild-type yeast strain during nitrogen starvation conditions. The trehalose content of wild type and Δtor1 yeast cells was similar in normal and nitrogen starved growth conditions. The accumulation of glycogen in Δtor1 mutants was higher than wild type at normal growth conditions. But, the nitrogen starvation triggered the glycogen accumulation 25-fold in wild type and 2-fold in mutant yeast cells. Nutrient replenishment has no considerable effect on the trehalose and glycogen content of mutant and wild type yeast cells. However, the reserve carbohydrate accumulation was continuously increase in non-replenished environment in mutant yeast cells. These results indicate that, TOR signalling pathway is more effective on glycogen metabolism. In addition, deletion of the TOR1 gene and inactivation of the gene product do not have the same effect on trehalose and glycogen metabolism.

International Journal of Natural and Engineering Science, 2022

Saccharomyces cerevisiae is used as a model organism for investigating the metabolic and genetic ... more Saccharomyces cerevisiae is used as a model organism for investigating the metabolic and genetic regulations in higher organisms. Glycogen is a storage carbohydrate in yeast cells and is used as an energy source. Glycogen is accumulated at the onset of the stationary phase and the logarithmic phase during different environmental and intracellular stress conditions. Glycogen level in the cell is regulated by different sensory and signaling pathways. TOR signaling pathway is activated when the environmental conditions are suitable, but it is repressed after rapamycin/caffeine treatment or nutrient starvation. In this study, the effect of the TOR signaling pathway on glycogen metabolism was determined with the Next Generation Sequencing method in S. cerevisiae. The total RNA isolated from yeast cells grown in a medium containing caffeine was used for the Next Generation Sequencing analysis. The differentially expressed genes after caffeine treatment were determined by comparing the caffeine-treated cells to untreated cells. It was determined that the transcription of 44% of the genes was expressed differentially after caffeine treatment, and 20% of differentially expressed genes were found to be up-regulated. The transcription of genes involved in glycogen metabolism, except PGM1, was up-regulated after caffeine treatment. The inactivation of Tor1p caused to increase in PGM2, UGP1, GLG1, GSY1, GSY2, GLC3, GPH1, and GDB1 transcription at least 2 fold. In silico analysis revealed that these genes include at least one STRE sequence in their promoter regions for binding of Msn2/4 transcription factors. It was observed that after caffeine treatment MSN2 transcription was down-regulated while MSN4 transcription was upregulated. This indicates that the Msn4 transcription factor was more effective than Msn2p in upregulating genes in glycogen metabolism. In conclusion, repression of the TOR signaling pathway by caffeine causes Msn4p-dependent transcriptional activation of genes involved in glycogen metabolism.

European Journal of Biological Research, 2021

Since yeasts can survive under variable environmental conditions using different food sources the... more Since yeasts can survive under variable environmental conditions using different food sources they have a wide distribution in nature. Fruits are suitable living spaces for yeasts and other microorganisms due to their high and different sugar contents. Strawberry fruit as well as other fruits are very sensitive to pathogenic fungi. Due to their residues on fruits, limitations on the use of fungicides have led to increased use of microorganisms with antagonistic effects as biological control agents. The biological agents to be used are selected mainly from the microorganisms found in the natural microbiota of the fruit. Therefore, in this study yeast biota on strawberry fruit collected from fungicide treated (Klorzon and Topas) and organic fields was determined using molecular identification methods. In addition, extracellular enzyme profiles of the identified yeast species were determined by the APIZYM-based system. There was no difference in the diversity of yeast species on strawberries collected from fungicide treated and organic fields, but the yeast density on organic strawberries was greater than fungicide treated fruits. The identified yeast species on fruits were determined as Metschnikowia pulcherrima (61.7%), Hanseniaspora uvarum (34.0%) and Wickerhamomyces pijperi (4.3%). W. pijperi yeast species was reported on strawberry fruit in our study first time. It was determined that H. uvarum and W. pijperi yeast species showed no α-glucosidase enzyme activity. All yeast strains showed industrially important β-glucosidase enzyme activity.

Crabtree Yeast , Sep 25, 2021

The use of fermentation in the presence of oxygen and at high glucose concentrations is referred ... more The use of fermentation in the presence of oxygen and at high glucose concentrations is referred to as the Crabtree effect. Yeast species that have the Crabtree effect are called Crabtree positive, and yeast species that do not have the Crabtree effect are called Crabtree negative. While Crabtree negative yeast strains are mostly used for heterologous protein production in the industrial field, Crabtree positive yeast strains are used to understand metabolic events in cancer cells. The genes encoding the enzymes involved in the glycolytic pathway in S. cerevisiae yeast cells are controlled by Gcr1p. Gcr1p binds to CT elements located in the promoter regions of glycolytic genes and activates their transcription. In our study, Crabtree positive and negative yeast strains containing ScGcr1p similar proteins were determined, and protein similarity analyzes and promoter analyzes of genes encoding the relevant proteins in these yeast strains were compared in silico using different databases and analysis programs. For this purpose, SGD, UNIPROT, NCBI-Genome and Yeastract databases and BLASTp-NCBI, MEGA-X and Chromatin Folding V2 programs were used. Using the SGD database, 32 different yeast strains were identified that matched with Sc-Gcr1p. Five different Crabtree positive and 5 different Crabtree negative yeast strains were selected from these yeast strains and in silico analyzes were performed using these yeast strains. After protein analysis and promoter analysis, it was determined that the similarities and differences between yeast species were not specific for Crabtree positive and Crabtree negative yeast species, but varied between species.

Raspberry Yeast, Extracellular Enzymes, 2021

Raspberry fruit contains phenolic compounds, flavones, flavonoids, vitamins, and antioxidant subs... more Raspberry fruit contains phenolic compounds, flavones, flavonoids, vitamins, and antioxidant substances that are important properties for health and pharmacological sciences. Edible berries provide also a suitable habitat for the growth of various microorganisms. In this study, yeast biota associated with raspberry fruits was
determined by molecular identification techniques. Raspberry fruits were collected from Çanakkale, Gelibolu (Gallipoli). Yeast strains were isolated and then identified by using the analysis of ITS1-5.8S-ITS2 rDNA gene sequences. The phylogenetic analysis of all yeast strains was carried out by using the MEGA – X phylogenetic analysis tool. The extracellular enzyme profiles of identified yeast species were determined by the API-ZYM kit system. The distribution of yeast species on the raspberry fruits was determined as Hanseniaspora uvarum, Metschnikowia viticola, Aureobasidium pullulans, and Metschnikowia pulcherrima . It was observed that yeast strains belong to Metschnikowia genus were dominant on raspberry fruits. All yeast strains in
Metschnikowia genus showed different enzyme profiles against seven extracellular enzymes. These enzymes may be the discriminatory enzymes for the yeast strains in the Metschnikowia genus. When the phylogenetic relationships among all yeast strains were investigated, all strains were divided into two main clades. While the first clade consists of only Metschnikowia genus, second clade includes H. uvarum and
A. pullulans yeast species. Our results indicated that restriction patterns and also extracellular enzyme profiles could be utilized for differentiation of yeast strains within the genus. M. pulcherrima, H. uvarum, and A. pullulans can be used for industrial applications for future researches.

Pomegranate related yeast, May 1, 2020

Yeasts are the most significant organisms to produce fermented products from different types of f... more Yeasts are the most significant organisms to produce fermented products from different types of fruits such as grape, strawberry and pomegranate. The native yeasts on these fruits contribute to beverages’ quality and aroma during fermentation. Pomegranate is used in fruit juice and wine production because of high antioxidant characteristic. In order to determine yeast microbiota on the pomegranate fruits collected from Gallipoli (Gelibolu), Çanakkale-Turkey, ITS-5.8S rDNA gene region have been utilized. Also, phylogenetic relationships among identified yeast species were assigned by using sequences of ITS-5.8S rDNA gene region. In addition, extracellular enzyme activity of identified yeast strainswas detected by using API-ZYM. Kluyveromyces lactis, Aureobasidium pullulans, Hanseniaspora uvarum, Candida zeylanoides, Kwoniella sp., and Metschnikowia pulcherrima and Metschnikowia ziziphicola yeast species were identified on pomegranate surface. Phylogenetic analysis, carried out in ITS-5.8S rDNA gene region of identified yeast strains, revealed the presence of five clades. Kwoniella sp., H. uvarum, M. pulcherrima, and Kl. lactic
yeast strains revealed high leucine arylamidase activity. Also valine arylamidase activity was determined in M. pulcherrima and Kl. lactis yeast species. Acid phosphatase activity was determined in H.uvarum and K. lactis yeast species. Uncultured Kwoniella sp. and H. uvarum yeast species displayed high β-galactosidase and β-glucosidase activities, respectively.