Food Biotechnology
Elham Rouhi; Alireza Sadeghi; Seyed Mahdi Jafari; Mohammad Abdolhoseini; Elham Assadpour
Abstract
< p >Introduction: Evaluation of probiotic and antifungal properties of lactic acid bacteria (LAB) isolated from fermented substrates has great importance in order to provide microbial cultures for fermentation industries. Among the fermented foods, dairy products play the main role as carriers ...
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< p >Introduction: Evaluation of probiotic and antifungal properties of lactic acid bacteria (LAB) isolated from fermented substrates has great importance in order to provide microbial cultures for fermentation industries. Among the fermented foods, dairy products play the main role as carriers of probiotics. Meanwhile, non-dairy fermented foods have been rarely studied in order to isolation and characterization of their probiotic microorganisms. Sourdough as a mixture of flour and water is a proper fermented ecosystem to isolate probiotic and antifungal LAB. Besides their desired health, probiotics must become active in the consumer''s gastrointestinal tract without any adverse effect. These bacteria can be used as starter, adjunct or preservative cultures to produce different fermented foods. Furthermore, antimicrobial metabolites of the LAB have also numerous potential applications as bio-preservatives in food and/or medical technologies. < p > < p >Materials and methods: In the present study, after continuous back-slopping process, predominant LAB was isolated from fermented quinoa. Then the LAB isolate was identified using PCR amplification of its partial 16S rDNA gene. Subsequently, probiotic properties of the LAB including its resistance to low pH and bile salt, antibacterial effects, aggregation potentials, antibiotic susceptibility and haemolytic activity were investigated. Antifungal effect of the LAB on Aspergillus niger was also determined using overlay bioassay. Finally, the one way analysis of variance (ANOVA) with the least significant difference (LSD) post hock (at p < /em> < p >Results and discussion: Sequencing results of the PCR products led to the identification of Enterococcus hirae as predominant LAB isolated from quinoa sourdough. Sourdough fermentation depends on the several technological and environmental factors and therefore, different types of these complex stressful ecosystems have their specific microflora with unique properties. The LAB isolate had proper survival after continuous pH and bile treatments. Resistance to low pH and bile salt is not sufficient to predict the survival of the probiotics in the actual conditions of the gastrointestinal tract. However, these properties are necessary for assessment of viability and activity in this situation. Furthermore, the highest antibacterial activity of the LAB was observed against Bacillus cereus among the studied food borne indicator bacteria. The effect of crude cell free supernatant (CFS) obtained from LAB isolate on indicator bacteria was significantly (p < /em>
