Histidine and tyrosine decarboxylase activities of lactic acid bacteria in sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax)

Biogenic amines (BAs) are formed by decarboxylation of amino acids, amination and transamination of aldehyde and ketone groups. The excess of BAs is harmful to human health. BAs play a significant role in determining the shelf life and quality of foods. Released type and amount of BAs depend on factors such as the quality of the raw material, the diversity of natural microbiota, processing and storage conditions. In fish, the release of BAs is affected primarily from microbial growth as well as other reasons and may cause poisoning. It was aimed to determine the possibility of histidine decarboxylase activity gene (hdc) and tyrosine decarbocylase activity gene (tyrdc) in lactic acid bacteria (LAB) which were isolated from sea bream and sea bass. A total of 18 Gram positive-catalase negative LAB was isolated from 84 fish samples from 14 different fish markets. It was found that 12 out of 18 LAB (67%) isolates showed negative histidine and tyrosine decarboxylase activities. While 2 out of 6 (11%) LAB isolates were determined positive only tyrosine decarboxylase and 4 of them (22%) were positive for histidine and tyrosine decarboxylase. As a result of the Polymerase Chain Reaction (PCR), 9 out of 12 LAB isolates (75%) were found to have histidine decarboxylase activity gene. As a result, the prevalence of histidine decarboxylase activity gene in the LAB has detected more extensive than tyrosine decarboxylase activity gene. Increasing the studies examining the presence of aminobiogenic microorganisms in fish is important for the protection of public health.