Evaluation of biogenic amines producing potential of bacteria associated with proteinous food

ABSTRACT

@#Aim: The aim of this study was to assay for the biogenic amine-producing capacity of bacteria isolated from proteinous food. Methodology and results: Previously characterized bacterial isolates (Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae) obtained from proteinous food samples (smoked fish and yoghurt) were subjected to proteolytic analysis using nutrient agar supplemented with 0.2 g/mL casein and decarboxylase activity using nutrient broth supplemented with 0.004 g/mL amino acids (histidine, tyrosine, asparagines, leucine and lysine). Isolates that expressed proteolytic and decarboxylase activities were screened for biogenic amine producing capacity using decarboxylase broth which was supplemented with an amino acid (tyrosine). Biogenic amines obtained in this research were classified into primary amine and secondary amine based on their qualitative characteristics. Confirmatory and quantitative analysis of biogenic amines produced was done using high-performance liquid chromatography. The confirmatory screening revealed the presence of methylamine, ethylamine, putrescine, cadaverine, histamine, spermidine, phernylethylamine, spermine, agmatine, tyramine, dopamine, tryptamine, norepinephrine and serotonin respectively. Total biogenic amines produced by S. aureus was 70.12 mg/kg, K. pneumoniae (62.58 mg/kg) and E. coli (56.57 mg/kg) respectively. Conclusion, significance and impact of study Enzymatic decarboxylation of free amino acids and other metabolic processes by the test organisms (S. aureus, E. coli and K. pneumoniae) leads to production of biogenic amines which can be used as a quality indicator in food in terms of degree of spoilage, use of non-hygienic raw material and poor manufacturing environment. Thus, effect of biogenic amines obtained in this research would be determined by individual toxicological threshold which can be extremely variable from few mg/kg in sensitive person to several hundred mg/kg in healthy person. The concentrations of each biogenic amine quantified are within the limit but their toxic effects depend on the type of amine, the presence of modulating compounds and the efficiency of an individual’s detoxification mechanism.