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Öğe Antimicrobial and functional properties of lactic acid bacteria isolated from sourdoughs(Academic Press, 2017) Demirbaş F.; İspirli H.; Kurnaz A.A.; Yilmaz M.T.; Dertli E.The technological and functional properties of 15 LAB species previously isolated from sourdough were determined in terms of antifungal and antibacterial activities, production of GABA as a functional component and phytase activity. All sourdough isolates were capable of producing GABA and Weissella paramesenteroides N-7 and Lactobacillus paralimentarius E-106 showed the highest and the lowest production levels as 18,43 mM and 3,39 mM, respectively determined by HPLC analysis. The antifungal activity of these strains were tested against Aspergillus niger and Penicillium chrysogenum and two strains Lactobacillus paraplantarum N-15 and L. paralimentarius E-106 showed significant inhibitory effects to these mould species. Generally, different levels of antibacterial activity of these species were observed against food-borne pathogens but only one strain showed low levels of inhibitory effect to Salmonella typhimurium but not the other strains. The PCR detection of several bacteriocin coding genes revealed that all strains were harboured at least one bacteriocin gene among the tested genes. Finally, all strains showed phytase activity but these activity was dependant on strain specific conditions. This study revealed some important techno-functional properties of sourdough LAB strains which can play crucial roles on sourdough technology. © 2017Öğe Characterization of a 4,6???glucanotransferase from Lactobacillus reuteri E81 and production of malto-oligosaccharides with immune-modulatory roles(Elsevier B.V., 2019) İspirli H.; Şimşek Ö.; Skory C.; Sağdıç O.; Dertli E.A wide number of Lactic Acid Bacteria (LAB) species produce ?-glucans with their ability to synthesize glucansucrases (GS) which use sucrose as substrate for the glucan production. Recently another group of enzymes in LAB gained special interest for their ability to produce ?-glucans targeting the substrates containing ?1-4-linkages and synthesizing new (?1-6) or (?1-3)–linkages as ??glucanotransferases. In this study, a putative 4,6???glucanotransferase (GTFB) from sourdough isolate Lactobacillus reuteri E81 was identified and expressed in Escherichia coli. The biochemical characterization of the GTFB-E81 confirmed its function as it cleaved the ?1-4-linkages in different substrates and produced new gluco-oligomers/polymers containing ?1-6 linkages together with the ?1-4-linkages detected by NMR analysis. GTFB-E81 produced malto-oligosaccharides targeting maltose and maltoheptaose as substrates with up to DP 8 detected by TLC and ESI-MS/MS analysis. The functional roles of these malto-oligosaccharides were determined by testing their immune-modulatory functions in HT29 cells and they triggered the production of anti-inflammatory 1L-4 and pro-inflammatory IL-12 cytokines. © 2018 Elsevier B.V.Öğe Characterization of functional properties of enterococcus faecium strains isolated from human gut(National Research Council of Canada, 2015) İspirli H.; Demirbaş F.; Dertli E.The aim of this work was to characterize the functional properties of Enterococcus faecium strains identified after isolation from human faeces. Of these isolates, strain R13 showed the best resistance to low pH, bile salts, and survival in the simulated in vitro digestion assay, and demonstrated an important level of adhesion to hexadecane as a potential probiotic candidate. Analysis of the antibiotic resistance of E. faecium strains indicated that in general these isolates were sensitive to the tested antibiotics and no strain appeared to be resistant to vancomycin. Examination of the virulence determinants for E. faecium strains demonstrated that all strains contained the virulence genes common in gut-and food-originated enterococci, and strain R13 harboured the lowest number of virulence genes. Additionally, no strain contained the genes related to cytolysin metabolism and showed hemolytic activity. The antimicrobial role of E. faecium strains was tested against several pathogens, in which different levels of inhibitory effects were observed, and strain R13 was inhibitory to all tested pathogens. PCR screening of genes encoding enterocin A and B indicated the presence of these genes in E. faecium strains. Preliminary characterization of bacteriocins revealed that their activity was lost after proteolytic enzyme treatments, but no alteration in antimicrobial activity was observed at different pHs (3.5 to 9.5) and after heat treatments. In conclusion, this study revealed the functional characteristics of E. faecium R13 as a gut isolate, and this strain could be developed as a new probiotic after further tests. © 2015, National Research Council of Canada. All Rights Reserved.Öğe Characterization of functional properties of Enterococcus spp. isolated from Turkish white cheese(Academic Press, 2017) İspirli H.; Demirbaş F.; Dertli E.Enterococcus species was isolated from Turkish white cheese and genotypic characterization of these isolates revealed the presence of 12 distinct strains belonging to 5 different species: Enterococcus faecium, E. faecalis, E. durans, E. gallinarum and E. italicus. All strains showed good survival ability under bile salt conditions. The antibiotic resistance of these strains was low but two strains showed high levels of resistance including resistance to vancomycin. PCR detection of virulence determinant in these isolates revealed that cheese isolate enterococci contained virulence genes common in gut and food originated enterococci and importantly two strains harboured cylB gene related to cytolysin metabolism. No complete hemolytic activity was observed for Enterococcus strains but partial hemolytic activity was observed 8 out of 12 strains. Additionally, all strains showed important levels of antimicrobial activity against food-borne pathogens and PCR screening of genes encoding enterocin A and B indicated the presence of enterocin B gene in all tested strains. The antimicrobial activities of the tested strains were lost after proteolytic enzyme treatments but no alteration was observed at different pHs and after heat treatments. In summary, this study reflected characteristics of Enterococcus strains presented in Turkish white cheese in terms of functional and safety perspectives. © 2016Öğe Glucan type exopolysaccharide (EPS) shows prebiotic effect and reduces syneresis in chocolate pudding(Springer, 2018) İspirli H.; Demirbaş F.; Dertli E.Exopolysaccharides (EPS) of lactic acid bacteria are important biopolymers that can improve the physicochemical properties of food products and act as prebiotics. In this study the physicochemical role and the prebiotic effects of a glucan type EPS with (?1-3) and (?1-6) linkages were assessed in chocolate pudding containing Lactobacillus rhamnosus GG as a probiotic strain. The functions of EPS were determined by developing three different formulations: control, probiotic (Lactobacillus GG) and symbiotic pudding (Lactobacillus GG + EPS) samples. The pH and acidity of the symbiotic pudding sample were higher than the probiotic and the control samples during the 28-day of storage period. Similarly, an important level of increment in Lactobacillus GG levels in symbiotic sample was observed compared to the probiotic sample suggesting the prebiotic role of the ?-glucan. Importantly, the syneresis in symbiotic pudding sample reduced significantly compared to other pudding samples which is related with the physicochemical role of glucan type EPS. This study reveals the prebiotic and physicochemical roles of ?-glucan type EPS in a chocolate pudding model. © 2018, Association of Food Scientists & Technologists (India).Öğe Impact of exopolysaccharide production on functional properties of some Lactobacillus salivarius strains(Springer Verlag, 2015) Mercan E.; İspirli H.; Sert D.; Yılmaz M.T.; Dertli E.The aim of this work was to characterize functional properties of Lactobacillus salivarius strains isolated from chicken feces. Detection of genes responsible for exopolysaccharide (EPS) production revealed that all strains harbored a dextransucrase gene, but p-gtf gene was only detected in strain E4. Analysis of EPS production levels showed significant alterations among strains tested. Biofilm formation was found to be medium composition dependant, and there was a negative correlation with biofilm formation and EPS production. Autoaggregation properties and coaggregation of L. salivarius strains with chicken pathogens were appeared to be specific at strain level. An increment in bacterial adhesion to chicken gut explants was observed in L. salivarius strains with the reduction in EPS production levels. This study showed that strain-specific properties can determine the functional properties of L. salivarius strains, and the interference of these properties might be crucial for final selection of these strains for technological purposes. © 2015, Springer-Verlag Berlin Heidelberg.Öğe Isolation and identification of exopolysaccharide producer lactic acid bacteria from Turkish yogurt(Blackwell Publishing Ltd, 2018) İspirli H.; Dertli E.Lactic acid bacteria (LAB) were isolated from traditional yogurt samples and genotypic characterization of these isolates revealed the presence of 21 distinct LAB strains belonging to Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, Leuconostoc mesenteroides, and Lactobacillus plantarum as new LAB strains. Determination of the exopolysaccharide (EPS) production characteristics of the selected strains of each species revealed that all strains possessed at least one gene required for both homopolymeric- and heteropolymeric-type EPS production. Structural analysis of the EPSs showed that L. delbrueckii subsp. bulgaricus Y39 and S. thermophilus Y102 produced heteropolymeric EPS containing glucose and galactose, whereas Leuc. mesenteroides Y35 and L. plantarum Y36 produced homopolymeric glucan-type EPS. The level of EPS production in these strains was found to be in a similar range. These strains with EPS production characteristics are good candidates for future studies as new LAB for yogurt production. Practical applications: Recent trends in yogurt production technology have led to an increased use of ropy starter cultures in yogurt production due to the technological roles of exopolysacharides (EPS) produced by these cultures. The main role of EPS in yogurt production is to improve the textural properties of yogurt as an in situ produced natural polymer. In addition to the yogurt starter cultures, use of adjunct cultures during production of yogurt is also of special interest to enhance the technological and nutritional characteristics of yogurt. Therefore, in this study, potential yogurt starter and adjunct cultures from traditional yogurt samples with EPS production characteristics were isolated. From these isolates, Lactobacillus delbrueckii subsp. bulgaricus Y39 and Streptococcus thermophilus Y102 produced heteropolymeric EPS containing glucose and galactose, whereas Leuconostoc mesenteroides Y35 and Lactobacillus plantarum Y36 produced homopolymeric glucan. © 2017 Wiley Periodicals, Inc.Öğe Physicochemical characterisation of an ?-glucan from Lactobacillus reuteri E81 as a potential exopolysaccharide suitable for food applications(Elsevier Ltd, 2019) İspirli H.; Sagdic O.; Yılmaz M.T.; Dertli E.Lactobacillus reuteri strain (E81) is an alpha glucan producer from traditional sourdough and the physicochemical characteristics of this glucan was determined in this study. The HPLC analysis confirmed the presence of glucose as the only sugar monomer in the repeating structure of this exopolysaccharide (EPS). The functional groups within the glucan structure was detected by FTIR analysis. The scanning electron microscopy (SEM) analysis demonstrated the web-like branched structure of the glucan. Morphological characterisation of the glucan E81 by atomic force microscopy (AFM) analysis showed clear roundness lumps and chains. Importantly, thermal characteristics of glucan E81 determined by thermogram analysis (TGA) and differential scanning calorimeter (DSC) analysis revealed that glucan E81 has a melting point of 290 °C making it promising to be used in thermal processed foods including sourdough bread. © 2018 Elsevier Ltd
