Characterization of tetragenococcus halophilus from Vietnamese fish mash

Abstract

In this study, the intracellular aminopeptidase activities and volatile’s profiles of seventeen Tetragenococcus halophilus strains, which were isolated previously from fish mash, were investigated. Among them, Tetragenococcus halophilus strains CH2-4 and CH6-2 exhibited the highest aminopeptidase activities of 2.1-2.2 U/mL toward Glutamic-pNA, while T. halophilus strains CH6-1 and V7-2 showed the highest aminopeptidase activities of 1.4-1.5 U/mL toward Leucine-pNA. The fish broth inoculated with T. halophilus strains CH2-4, CH6-2, CH6-1 and V7-2 for 14 days were treated to obtain the volatiles before being subjected to GC/MS analysis. A total of 19 volatile compounds, including esters (pentanoic acid, 2-ethylhexyl ester; pentanoic acid, 2-propenyl ester), alcohols (3-hexanol; 2-ethyl-1-hexanol; 2-furanmethanol), ketones, phenols, hydrocarbons and sulfur containing compounds (sulfurous acid, butyl 2-ethylhexyl ester and benzyl 2-chloroethyl sulfone) were identified. The groups of esters and alcohols were the most abundant based on the phenomena that 6 compounds were identified in each group. T. halophilus CH6-2 strains produced the highest amount of identified volatile compounds. Among 19 volatile compounds identified, 10 were detected in sample inoculated with strains CH6-2, while only 5 to 6 volatile compounds were observed in the samples inoculated with the other strains. The strains T. halophilus CH6-2 could tolerate NaCl concentration of 25 %. The optimal condition for its growth was at 5-8 % of NaCl, pH of 6.5 to 7.5 and temperature of less than 37 °C.