Molecular identification and probiotic properties of ‘lactobacillus acidophilus group’ isolates from Turkish kefir/

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2014

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Gülel, Şebnem

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Lactic acid bacteria (LAB) are Gram-positive, non-spore-forming, rods, cocci or coccobacilli that ferment glucose primarily to lactic acid, or lactic acid, carbon dioxide and ethanol. These bacteria are among the most important group of microorganisms used in food and beverage fermentations. Lactobacillus species comprise the major part of LAB and a number of them are used as probiotic strains in order to benefit human health. In this study, four ‘Lactobacillus acidophilus group’ isolates from Turkish kefir were identified by using molecular identification techniques and also investigated for their probiotic characteristics. Their molecular identification was done by sequence comparison of PCR (polymerase chain reaction) amplified V1 region of the 16S rRNA gene, isolated from the strains, with sequences of Lactobacillus acidophilus group type strains. The comparison identified all four kefir isolates of Lactobacillus acidophilus group as Lactobacillus amylovorus. The identified strains were further investigated for their probiotic properties, including acid tolerance, bile salt tolerance and cell surface hydrophobicity. A commercial probiotic strain, LA05, was also investigated in order to use its data as a reference for kefir isolates. All of these strains were also tested for antibiotic susceptibility to determine the existing antibiotic resistant genes that might be involve in horizontal gene transfer. Antibiotics belonging to the groups of inhibitors of cell wall synthesis, inhibitors of protein synthesis, inhibitors of nucleic acid synthesis and inhibitors of cytoplasmic membrane were used. All kefir isolates showed high tolerance against both acid and bile salts, but exhibited low hydrophobicity. They showed high resistance to nucleic acid synthesis inhibitors and cytoplasmic membrane inhibitors, but low resistance to the inhibitors of cell wall synthesis and to the majority of protein synthesis inhibitors. The results were the same for the commercial probiotic, the strain LA05. Since in vitro analyses do not necessarily correlate in vivo analyses, these results are sufficient to consider these ‘Lactobacillus acidophilus group’ isolates from Turkish kefir as promising candidates for use as commercial probiotic strains.

Subject Keywords

Probiotics., Kefir., Lactobacillus acidophilus., Molecular biotechnology.

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http://etd.lib.metu.edu.tr/upload/12617589/index.pdf
https://hdl.handle.net/11511/23693

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

Ş. Gülel, “Molecular identification and probiotic properties of ‘lactobacillus acidophilus group’ isolates from Turkish kefir/,” M.S. - Master of Science, Middle East Technical University, 2014.