Comparative evaluation of hydrolysates as a basis for the construction of a nutrient medium for the cultivation of <i>Listeria monocytogenes</i>

Abstract

The objective is to perform a comparative evaluation of the pancreatic hydrolysates prepared from fish and squid to determine the optimal culture medium for Listeria monocytogenes.Materials and methods. The following raw materials were used in the study: Pacific Herring (Clupea pallasii), Alaska Pollock (Gadus chalcogrammus), Common Roach (Rutilus rutilus lacustris), European Squid (Loligo vulgaris). The raw materials were subjected to enzymatic hydrolysis using the pancreas (according to Hottinger). A study of the physicochemical properties of pancreatic hydrolysates (content of free amino nitrogen (FAN), acidity of fish hydrolysates, the amino acid composition) was carried out.. The specific activity of nutrient media during the cultivation of the test strain L. monocytogenes 766 was assessed by a complex of microbiological methods.Results and discussion. The highest content of FAN at the end of enzymatic hydrolysis was observed in the pancreatic hydrolysate of the common roach (6%), the acidity of the hydrolysate remained stable from 6th to 13th day of the hydrolysis process (pH 7.2). Pancreatic hydrolysate of the common roach contained a number of amino acids that are most essential for the growth of Listeria. An assessment of the biological properties of nutrient media prepared on the basis of the obtained hydrolysates demonstrated that the best results in terms of sensitivity and germination of L. monocytogenes 766 showed a nutrient medium based on the pancreatic hydrolysate of the common roach. During the cultivation of L. monocytogenes 766 the test strain retained its morphological and cultural properties and did not show signs of dissociation.Conclusion. The research results have shown that the pancreatic hydrolysate of the common roach is a promising protein basis for the construction of an experimental environment for listeria.