Staphylococcus sp. CMC5-3-1 and CMS5-7-5 isolated from fermented fish sauce at 3 to 7 mo, respectively, showed different characteristics on protein hydrolysis and volatile formation. These Gram-positive cocci were able to grow in up to 15% NaCl with the optimum at 0.5% to 5% NaCl in tryptic soy broth. Based on ribosomal 16S rRNA gene sequences, Staphylococcus sp. CMC5-3-1 and CMS5-7-5 showed 99.0% similarity to that of Staphylococcus piscifermentans JCM 6057(T) , but DNA-DNA relatedness was <30%, indicating that they were likely to be new species. DNA relatedness between these 2 strains was only 65%, suggesting that they also belonged to different species. The α-amino group content of 6-month-old fish sauce inoculated with Staphylococcus sp. CMC5-3-1 was 740.5 mM, which was higher than that inoculated by the strain CMS5-7-5 (662.14 mM, P < 0.05). Histamine was not produced during fermentations with both strains. Fish sauce inoculated with Staphylococcus sp. CMC5-3-1 showed the highest content of total glutamic acid (P < 0.05). The major volatile compound detected in fish sauce inoculated with Staphylococcus sp. CMC5-3-1 was 2-methypropanal, contributing to the desirable dark chocolate note. Staphylococcus sp. CMC5-3-1 could be applied as a starter culture to improve the umami and aroma of fish sauce.
Keywords: 16S rRNA gene; DNA-DNA hybridization; Staphylococcus sp; fish sauce; glutamic acid; volatile compounds.
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