Вестник МГТУ, 2024, Т. 27, № 3.

Живлянцева Ю. В. и др. Использование белкового гидролизата из вторичного рыбного сырья. The productivity of culture medium was assessed as the degree of growth of the target microorganism on the culture medium when compared with culture agar for the cultivation of microorganisms GRM (GOST ISO 11133-2016) under certain conditions and was calculated by the formula P r = Nc /N 0 , (2) where PR - the coefficient of productivity of culture medium; Nc - the arithmetic mean of the number obtained on the culture medium subjected to the test (for example, the number of colonies in plates); N0 - the arithmetic mean of the amount obtained on a certain control culture medium. The coefficients of productivity of culture medium are presented in Table 5. Table 5. Coefficient of productivity of culture medium Таблица 5. Коэффициенты производительности Name Salmonella enteriditis № 5765 Staphylococcus aureus ATCC 25923 Tested culture medium based on a prototype fish protein hydrolysate 1.00 1.09 Nutrient agar for the cultivation of microorganisms, dry GRM 1 1 Description o f the obtained results The results are considered valid when the following conditions are met: - a positive quantitative result (target bacterial growth) must be obtained for each plate; - each individual declared result falls within the standard assay range (no more than 100 colonies for methods with filtration and no more than 150 colonies for surface methods). PR should be at least 0.70 when comparing non-selective media with non-selective control media according to GOST ISO 11133-2016. The biochemical characteristics of colonies of microorganisms grown on the studied media were investigated. The work used microorganisms with stable characteristics, which are the causative agents of the most dangerous food poisoning. The most common analogue of fish protein hydrolysate is pancreatic fish meal hydrolysate. According to GOST 29311-92 "Pancreatic hydrolysates for bacterial culture media. General specifications" the main defining indicators of this type of products are the mass fraction of total and amine nitrogen, confirming the presence of the required number of nitrogenous compounds necessary for the life of microorganisms. For pancreatic fish meal hydrolysate, which is used for the preparation of culture media, the value of the mass fraction of amine nitrogen should be at least 0.3 %, total nitrogen - at least 0.75 %. According to TU 480-00001927 "Pancreatic hydrolysate of fish meal. Specifications" the mass fraction of amine nitrogen must be at least 2.8 %, total nitrogen - at least 8 %. According to Table 2, it can be seen that the corresponding values of the experimental fish protein hydrolysate are higher (3.60 and 12.97 %, respectively). It indicated the sufficiency of nitrogenous nutrients in the sample under study. Microbiological studies have established that the nature of the growth of test cultures on the studied culture medium using a test sample of fish protein hydrolysate as a protein component and control nutrient agar are identical. Discussion Coefficient of productivity of culture media has shown an efficiency of microbiological culture media. The studied culture medium showed high productivity ratio (Pr = 1, Pr = 1.09) when cultivating Salmonella enteriditis No. 5765 and Staphylococcus aureus ATCC 25923, respectively, which was at the level and even slightly higher than the performance values of the control medium and significantly exceeded the requirements for productivity (PR more than 0.7) established in GOST ISO 11133-2016. The test microorganisms after cultivation on the studied nutrient media based on fish protein hydrolysate retained their biochemical characteristics during the identification of microorganisms using test systems (Scientific and Production Association "Microgen", Russia). Bacteria of the genus Salmonella retained their gram-negative Gamma colour, the growth pattern on three-sugar ferruginous agar did not change (they ferment glucose and do not ferment lactose and sucrose, form hydrogen sulphide). Bacteria of the genus Salmonella do not form acetoin (Voges-Proskauer reaction is negative). Salmonella bacteria ferment mannitol. Agglutination (presence of O-antigens) is manifested in the form of sticking of the bacterial mass and full or partial clarification of the liquid (according to GOST 31659-2012 "Food products. Method for detecting bacteria of the genus Salmonella"). Bacteria of the genus Staphylococcus aureus retain a gram-positive Gram colour, give a positive reaction to catalase, form acetoin and ferment maltose under aerobic conditions. They have the ability to coagulate rabbit 298