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KMID : 1024620070270040509
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Food Science of Animal Resources
2007 Volume.27 No. 4 p.509 ~ p.516
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Identification and Characterization of Lactic Acid Bacteria Starters Isolated from the Commercial Drink-Yogurt Products
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Jeon Sang-Rok
Song Tae-Suk
Kim Ji-Youn
Shin Won-Cheol
Her Song-Wook
Yoon Seong-Sik
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Abstract
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Starters of lactic acid bacteria(LAB) were isolated from the commercial yoghurt products and the four isolates have been studied on their identification and some physiological characteristics. For the purpose of identification, microscopic examination, API test, and 16s rRNA gene sequencing were conducted. Isolate A from a yogurt product of local dairy company A was shown to be Gram-positive rod-shaped bacterium. All strains isolated were turned out to be as Lactobacillus paracasei by using a API 50 CHL kit. In contrast, isolate A was identified as a strain of Lactobacillus helveticus based on the 16S rRNA sequencing data, and L. casei ssp. casei for both B and D and L. paracasei for C. All the isolates survived the simulated gastric juice, pH 2.0 within 3 hours and sharply decreased in viability so that no viable cell was observed after 4.5 hours incubation. In addition, the four isolated strains were almost identical in antibiotic susceptibility to six different kinds of antibiotics including erythromycin (), ampicillin (), gentamycin (), neomycin (), but rather resistant to colistin () and streptomycin (). It was noteworthy that four isolates were confirmed to produce antibacterial substance against foodborne pathogens of Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli 0157:H7 as test organisms based on the inhibitory zones on an MRS soft agar medium. At presence, the inhibitory factor is unknown so that further studies are required to ascertain the active factor responsible for the inhibitory activities.
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KEYWORD
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Lactic acid bacteria, starters, drink-yogurt, identification, characterization
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