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Author: search.filters.author.Jaichalad, Thitirut

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    Lactic acid bacteria isolated from raw and fermented pork products: Identification and characterization of catalase-producing Pediococcus pentosaceus
    (2017-02-01)
    Nanasombat, Suree
    ;
    Treebavonkusol, Patcharee
    ;
    Kittisrisopit, Sunisa
    ;
    Jaichalad, Thitirut
    ;
    Phunpruch, Saranya
    Lactic acid bacteria (LAB) from raw and fermented pork samples were screened for their inhibitory activity by an agar spot test in order to obtain a LAB strain with suitable property to be used as meat starter cultures. Among the 174 isolates, 73 were positive to inhibit at least one of the seven indicator bacteria, which were further characterized. The most suitable isolate was isolate P0805, identified as Pediococcus pentosaceus. This bacterium was catalase- and nitrate reductase-positive and amino acid decarboxylase-negative; moreover, it produced inhibitory substances against Salmonella Typhimurium with the activity of the partially purified inhibitory substances of 409,600 AU/mL. To further characterize the catalase-producing ability of P. pentosaceus P0805, the effect of hematin on its catalase activity in Sausage Model Broth (SMB) was evaluated, and it enhanced catalase production. The catalase activity was found in both SMB with and without hematin. It was concluded that catalase produced by this bacterium was heme-independent catalase.
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    Screening and identification of lactic acid bacteria from raw seafoods and thai fermented seafood products for their potential use as starter cultures
    (2012-01-01)
    Nanasombat, Suree
    ;
    Phunpruch, Saranya
    ;
    Jaichalad, Thitirut
    The number of lactic acid bacteria (LAB) was analyzed from 52 samples of raw seafoods (shrimp and mussel), and Thai fermented seafood products including fermented shrimp (kung-jom), mussel (hoi-dong), and fish (pla-jom). The viable LAB were 3.0×10<sup>3</sup> to 3.4×10<sup>8</sup> CFU/g. LAB were isolated and screened for their inhibitory activities against eight indicator bacteria by agar spot test. Among all selected LAB isolates, 52 isolates showed strong inhibitory activity. They were further characterized for their ability to resist hydrochloric acid, lactic acid, bile salts, and sodium chloride, and their ability to produce bacteriocins and amino acid decarboxylase. The selected LAB isolates, 1IS11 and 4IS17, were bacteriocin-producing strains, and showed no amino acid decarboxylase activity, which was suitable property for starter cultures. The isolate 1IS11 could resist both hydrochloric and lactic acid at the lowest pH of 2.0, while the isolate 4IS17 was able to tolerate hydrochloric and lactic acid at the lowest pH of 1.5 and 2.0, respectively. Both isolates could grow in MRS broth containing a high concentration of sodium chloride (10 %) and bile salts (1.5%). They were identified by morphological characterization, biochemical test, and 16S rDNA sequence analysis. The isolate 1IS11 was found to be Enterococcus faecium, whereas the isolate 4IS17 was Enterococcus faecalis.
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    Characterization of the antibacterial activity and probiotic properties of lactic acid bacteria isolated from raw fish and nham-plaa
    (2008-10-01)
    Nanasombat, Suree
    ;
    Phunpruch, Saranya
    ;
    Sriwong, Niracha
    ;
    Jaichalad, Thitirut
    ;
    Onnom, Waragul
    Isolates of lactic acid bacteria from fish fillets and nham-plaa were screened to select the most suitable strains for the formulation of starter cultures with probiotic properties. Using an agar spot test, 30 of the 180 isolates that were tested inhibited at least one of four indicator strains; Staphylococcus aureus TISTR 118, Pediococcus acidilactici TISTR 051, Lactobacillus bulgaricus TISTR 415 and Listeria monocytogenes DMST 11256. Two bacterial isolates, 13IS3 and 13IS4, from fish fillets were resistant to a low pH in lactic acid (pH 2.9-3.2) and in HCl (pH 2.2) and a high concentration of NaCl (6.0%) and bile salts (5.25%). These isolates were identified by morphological, biochemical and molecular analysis as Lactococcus lactis 13IS3 and Lactobacillus sakei 13IS4. The fermentation of nham-plaa model broth (NMB) by L. lactis 13IS3 seemed to be stimulated by 1.0% garlic extract and 0-1.5% NaCl at all temperatures of incubation. L. sakei 13IS4 fermented at a slower rate than L. lactis 13IS3, but fermented more rapidly in a 3.0%-garlic extract NMB with 0-1.5% NaCl at 30°C and in the same medium containing 1.0-1.5% NaCl at 35°C.