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    Multilocus sequence typing of L. bulgaricus and S. thermophilus strains from Turkish traditional yoghurts and characterisation of their techno-functional roles
    (Korean Society Food Science & Technology-Kosfost, 2024) Dikmen, Hilal; Goktas, Hamza; Demirbas, Fatmanur; Kayacan, Selma; Ispirli, Humeyra; Arici, Muhammet; Turker, Mustafa
    In this study, Streptococcus thermophilus and Lactobacillus bulgaricus strains from traditional Turkish yoghurts were isolated, identified by 16S rRNA sequencing and genotypically 14 S. thermophilus and 6 L. bulgaricus strains were obtained as distinct strains by MLST analysis. Lactic acid production levels of the L. bulgaricus strains were higher than S. thermophilus strains. HPLC analysis showed that EPS monosaccharide composition of the strains mainly consisted of glucose and galactose. In general, all strains were found to be susceptible for antibiotics, except some strains were resistance to gentamicin and kanamycin. Apart from two strains of S. thermophilus, all strains displayed strong auto-aggregation level greater than 95% at 24 h incubation. S. thermophilus strains showed higher cell surface hydrophobicity than L. bulgaricus strains. This study demonstrated the isolation, identification, genotypic discrimination and techno-functional features of wild type yoghurt starter cultures which can potentially find place in industrial applications.
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    Physicochemical and structural characterisation of a branched dextran type exopolysaccharide (EPS) from Weissella confusa S6 isolated from fermented sausage (Sucuk)
    (Elsevier, 2024) Ozpinar, Fatma Beyza; Ispirli, Huemeyra; Kayacan, Selma; Korkmaz, Kader; Dere, Sevda; Sagdic, Osman; Alkay, Zuhal
    Exopolysaccharide (EPS) producing Lactic Acid Bacteria (LAB) species can be presented in distinct environments. In this study, Turkish fermented sausage (sucuk) was tested for the presence of EPS producer LAB strains and slimy-mucoid colonies were selected for further tests. Among the isolates, Weissella confusa strain S6 was identified and tested for the physicochemical characterisation of its EPS. This strain was found to produce 0.74 g L-1 of EPS in modified BHI medium conditions. Structural characterisation of EPS S6 by 1H and 13C NMR demonstrated that EPS S6 was a highly branched dextran type glucan formed by mainly (1 -* 2)-linked alpha-D- glucose units together with low levels of (1 -* 3)-linked alpha-D-glucose units as branching points. This structure was further confirmed by methylation analysis detected by GC-MS. An average molecular weight of 8 x 106 Da was detected for dextran S6. The FTIR analysis supported the dextran structure and revealed the presence of distinct functional groups within dextran S6 structure. A strong thermal profile was observed for dextran S6 detected by DSC and TGA analysis and dextran S6 revealed a degradation temperature of 289 degrees C. In terms of physical status, dextran S6 showed amorphous nature detected by XRD analysis. SEM analysis of dextran S6 demonstrated its rough, compact and porous morphology whereas AFM analysis of dextran S6 detected in its water solution showed the irregularity with no clear cross -link within the dextran chains. These technological features of dextran S6 suggests its potential to be used for in situ or ex situ application during meat fermentations.