Amino acid-decarboxylase activity of bacteria isolated from ice-preserved anchovies

Abstract

The amino acid-decarboxylase activity of bacteria isolated from Engraulis encrasicholus preserved in ice was investigated throughout 23 days of storage. A total of 140 bacterial isolates were studied, including 37 enterobacteria, 23 pseudomonads, 49 Gram+ catalase+ cocci, 27 lactic acid bacteria and 4 enterococci. The percentage of strains that decarboxylated amino acids was low, 12% on average. None of the Gram+ catalase+ cocci showed aminogenic activity, but all enterococci isolates did. The enterobacteria with aminogenic capacity were identified as Enterobacter cloacae and they simultaneously produced putrescine and cadaverine (up to 500 mg/l), but not histamine. Among pseudomonads, two species decarboxylated ornithine (producing 350–650 mg/l putrescine): Pseudomonas cepacia and Pseudomonas fluorescens. Lactic acid bacteria decarboxylated tyrosine, yielding up to 2,000 mg/l tyramine, and they were identified as Lactobacillus brevis, Lactococcus lactis, Pediococcus pentosaceous and Enterococcus spp. As a general rule, the positive Gram-negative isolates (enterobacteria and pseudomonads) were diamine producers and they were found only during the first 2 weeks of storage. In contrast, lactic acid bacteria and enterococci were mainly tyramine producers and they were isolated only at the end of storage.