Food Biotechnology
Sara Shahryari; Alireza Sadeghi; Maryam Ebrahimi; Alireza Sadeghi Mahoonak; Ali Mayedi
Abstract
[1]Introduction: Evaluation of antimicrobial and probiotic properties of the microbiota isolated from fermented pseudo-cereals is important in order to prepare adjunct and starter cultures. Probiotics are live and active microorganisms that, if used in sufficient numbers, help the microbial balance of ...
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[1]Introduction: Evaluation of antimicrobial and probiotic properties of the microbiota isolated from fermented pseudo-cereals is important in order to prepare adjunct and starter cultures. Probiotics are live and active microorganisms that, if used in sufficient numbers, help the microbial balance of the gastrointestinal tract and improve its function. Probiotics are also used as a substitute for antibiotics and synthetic preservatives in the prevention and treatment of complications of many infectious and pathogenic gastrointestinal pathogens. Probiotic microorganisms include lactic acid bacteria (LAB) and yeasts, and despite numerous reports on the probiotic properties of LAB, the probiotic properties of yeasts are less reported. Probiotic yeasts are organisms resistant to antibacterial compounds and effective against pathogens, which can rapidly increase their population in the gastrointestinal tract. These yeasts have several properties such as antimicrobial effects, resistance to acid and bile, binding to mucosal surfaces, inhibitory activity against pathogens and also the inability to transmit antibiotic resistance genes. In the present study, after isolation of the predominant yeast from buckwheat sourdough, the probiotic and antifungal properties of the isolate were investigated. Based on the literature review, no study has been presented to evaluate the probiotic and antifungal capabilities of yeasts isolated from buckwheat sourdough. Materials and Methods: In the present study, predominant yeast was isolated from buckwheat sourdough, and then it was identified using PCR. Subsequently, probiotic properties of the isolate including survival in present of low pH and bile salt, antibacterial effect, antibiotic susceptibility assay, aggregation, hydrophobicity, haemolytic activity as well as its antifungal activity against Aspergillus niger and Aspergillus flavus were studied. After spontaneous fermentation of buckwheat, predominant yeast was isolated using ten-fold dilution of the sourdough sample and its spread plating. The predominant isolate was identified through PCR amplification of a 650 bp target sequence from its ribosomal gene and sequencing of the PCR product. Then, survival of the yeast was determined at pH=2 and 0.3% bile salt as simulated gastrointestinal conditions. Subsequently, simultaneous culture of the yeast with some food-borne indicator bacteria in chromogenic media was used to investigate the inhibitory activity of the isolate against the studied bacteria. After that, resistance of the yeast isolate against the common antibiotics and some antimycotic agents was evaluated using disc method. Co-aggregation ability and hydrophobicity capability of the isolate were also determined based on the absorbance tests. In vitro safety of the yeast isolate was checked through its cultivation on blood agar containing sheep blood. Next stage, overlay bioassay was conducted to investigate antifungal effect of the yeast on the selected fungi. Finally, one way analysis of variance (ANOVA) with the least significant differences (LSD) post hock at p<0.05 was used for statistical analysis of the data. Results and Discussions: Sequencing results of the PCR products led to the identification of Pichia kudriavzevii as predominant yeast isolated from buckwheat sourdough. Survival rate of the isolate after treatment in simulated gastrointestinal conditions was 79.26% in comparison with the control. Antibacterial effect of the isolate on Escherichia coli was also significantly (P<0.05) higher than the other studied food-borne agents. Meanwhile, the growth of Listeria monocytogenes was decreased 19.50% in the present of the isolate. Whereas, the yeast isolate had no inhibitory effect on Salmonella enterica. Hydrophobicity and auto-aggregation capabilities of the isolate were also 64.07 and 67.40%, respectively. Furthermore, the isolate showed resistance towards all of the antibiotics tested, while it was resistant against ketoconazole and fluconazole, and the yeast was semi-sensitive towards itraconazole as antimycotic agents. The yeast isolate had no hemolytic activity, and its antifungal activity against A. niger and A. flavus was also verified. Accordingly, it is concluded that P. kudriavzevii isolate exhibits proper potential to be used as probiotic or protective culture in fermentation industries.In accordance with the results, probiotic characteristics of P. kudriavzevii (as the predominant yeast isolated from buckwheat sourdough) were approved. Accordingly, the isolate can be used as a potential probiotic culture in food industries.
Maryam Ebrahimi; Morteza Khomeiri; Yahya Maghsoudlou
Abstract
Introduction:Toxigenic fungi such as A. flavus grow widely in peanut and produce aflatoxins, a group of carcinogenic metabolites. Aflatoxin produced in peanut differed from the genetic variety of plant. The high humidity and moderate temperatures in the subtropical Caspian littoral of northern Iran could ...
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Introduction:Toxigenic fungi such as A. flavus grow widely in peanut and produce aflatoxins, a group of carcinogenic metabolites. Aflatoxin produced in peanut differed from the genetic variety of plant. The high humidity and moderate temperatures in the subtropical Caspian littoral of northern Iran could increase the growth of A. flavus and the production of aflatoxin. The objectives of this study were 1) to determine the chemical composition of peanut cultivars grown in Golestan Province, Iran, 2)to select resistant variety of peanut to aflaoxigenic A. flavus growth and 3) to evaluate relationship between A. flavus growth and changes in oleic and linoleic acid content and peroxide value. Materials and method: Peanut samples were used from four important varieties of peanut, Goli, Mahalli, China and India. those have been harvested from farms in Golestan province, Iran. Fat, protein, ash, moisture, reducing sugar, AFB1 content and peroxide value in each sample were measured by the standard method of AOAC. Fatty acids of the peanut seed oil were analyzed using gas chromatography (GC, Varian CP-3800 model) with a flame ionization detector (FID) and a DB-WAX column (50 m × 0.32 mm ×0.2 µm). To study the effects of A. flavus on peanut varieties, they were sterilized with 0.5% NaClO solution and then one ml of A. flavus spore suspension was added to every 20gr disinfected peanut and was placed in the incubator for eight days at 26°C. After incubation, the number of seeds colonized by fungi, spore production, AFB1 production, the association between colonization rate of hydrolysis of fatty acids and peroxide value were determined.Results and Discussion: The results showed that there were significant differences (P
