Screening and identification of lactic acid bacteria from raw seafoods and Thai fermented seafood products for their potential use as starter cultures

Abstract

The number of lactic acid bacteria (LAB) was analyzed from 52 samples of raw seafoods (shrimp and mussel), andThai fermented seafood products including fermented shrimp (kung-jom), mussel (hoi-dong), and fish (pla-jom). The viableLAB were 3.0103 to 3.4108 CFU/g. LAB were isolated and screened for their inhibitory activities against eight indicatorbacteria by agar spot test. Among all selected LAB isolates, 52 isolates showed strong inhibitory activity. They were furthercharacterized for their ability to resist hydrochloric acid, lactic acid, bile salts, and sodium chloride, and their ability toproduce bacteriocins and amino acid decarboxylase. The selected LAB isolates, 1IS11 and 4IS17, were bacteriocin-producingstrains, and showed no amino acid decarboxylase activity, which was suitable property for starter cultures. The isolate 1IS11could resist both hydrochloric and lactic acid at the lowest pH of 2.0, while the isolate 4IS17 was able to tolerate hydrochloricand lactic acid at the lowest pH of 1.5 and 2.0, respectively. Both isolates could grow in MRS broth containing a highconcentration of sodium chloride (10 %) and bile salts (1.5%). They were identified by morphological characterization, biochemicaltest, and 16S rDNA sequence analysis. The isolate 1IS11 was found to be Enterococcus faecium, whereas the isolate4IS17 was Enterococcus faecalis.

Keywords

• lactic acid bacteria
• seafood products
• bacteriocins
• biogenic amine
• probiotic
• starter culture