STUDY OF AROMATIC COMPONENTS IN THE COURSE OF INITIATING ENZYMATIC REACTIONS IN THE EDIBLE MUSHROOM PLEUROTUS OSTREATUS

Various branches of the food and medical industries widely use mushrooms, that is why their aromatic characteristics are quite important. This paper presents a comparative analysis of the aromatic and fatty acid composition of the mycelium of the edible oyster mushroom (Pleurotus ostreatus (Jacq.) P. Kumm., strain K-17) cultured on a glucose-peptone-yeast growth medium with wheat bran added. The quantitative and qualitative composition of the aromas has shown that wheat bran components affect the aroma-forming reactions during the growth of the mycelium of P. ostreatus. It has been established that the introduction of wheat bran increases the content of 1-octen-3-ol, the main fungal aromatic component. In the culture liquid, 1-octen-3-ol increases by 1.4 times, as compared with classic samples cultured on a growth medium without wheat bran. Also, in the mycelium cultured on a wheat bran-containing growth medium, the total quantity of identified aromatic components increases by 1.7 times. In this mycelium, the two main components of the mushroom’s aroma are formed: 1-octen-3-ol and hexanal. In other samples, these important components are absent. The results of this study confirm that the formation of the two main fungal aromatic components, 1‑octen-3-ol and hexanal, involves polyunsaturated fatty acids, namely linoleic acid. Its content decreased in parallel with the accumulation of aromatic components throughout culturing in the wheat bran-containing medium. The data obtained allow establishing how initiation of enzymatic oxidative reactions changes the aroma of P. ostreatus during surface culturing on a liquid medium. The research results reveal the regular patterns in the formation of aromatic components of macromycetes from lipid precursors. Addition of wheat bran to a growth medium unbalances the total content of aromatic components towards their accumulation in the mycelium. Since fruiting bodies and vegetative mycelium are similar in their biochemical composition, the results of studying the mycelium cultured on a liquid medium allow predicting how aromatic components will be formed in the fruiting bodies of oyster mushrooms.

PROSPECTS OF USING BY-PRODUCTS OF POTATO STARCH PRODUCTION AS COMPONENTS OF GROWTH MEDIA FOR LACTIC ACID BACTERIA CULTIVATION

The paper is concerned with the search for inexpensive alternative components of substrates of culture media for lactic acid bacteria. To be used in the food industry more extensively, lactobacilli should be produced in larger volumes. Bacteria-growing enterprises and those manufacturing probiotic preparations are interested in non-traditional components of growth media. However, it is quite a problem to create a cheap growth medium, because lactobacilli are very demanding of the content of certain components. Traditional culture media can include up to 40 components (peptones, yeast and vegetable extracts, vitamins, etc.). The research has proved that waste and by-products of potato starch production (potato juice and juice-containing water) can be used as components of a substrate to culture lactobacilli on. The strain used in the research was Lactobacillus plantarum 8R-A3. The growth kinetics of lactic acid bacteria has been analysed on different vegetable extracts. Tomato and cabbage extracts were used as traditional components of synthetic media to compare with. The findings have shown that on a substrate from by-products of potato starch production, after 96 hours of culturing at 37°C, the accumulation of Lactobacillus plantarum biomass is 20 g/l (on juice-containing water) and 25 g/l (on potato juice). Accumulation of bacteria wet weight has also been confirmed by determining the kinematic viscosity of the culture fluid. This parameter for potato juice after thermostatting was 6.77 mm2/s, which was somewhat higher than the viscosity of the tomato and cabbage extracts. It has been proved that by-products of potato processing ensure sufficient growth of lactic acid bacteria biomass. On the fourth day, the number of bacteria was 3·108 CFU/cm3. It has been shown how practical it is to use potato processing by-products as growth media substrates in culturing lactic acid bacteria Lactobacillus plantarum.

MATHEMATICAL MODELLING OF THE TECHNOLOGY OF PROCESSING THE SEED MASS OF VEGETABLES AND MELONS

Designing modern seed processing machines requires a study of the regularities of technological processes, dynamics and conditions of operation. To determine the control parameters and their optimum values, it is necessary to use high-precision mathematical models of technologies of processing the vegetable and melon seed mass. A method has been suggested of modelling the technology of processing the seed mass of vegetables and melons based on nonlinear canonical decomposition of a random sequence of changes in the technological process parameters. The method of modelling the technology of processing the seed mass of vegetables and melons can be used to determine the optimum values of design and operation parameters of seed separating machines. This method allows obtaining mathematical models of technological processes for an arbitrary number of input parameters used to evaluate the characteristics of seeds, the degree of nonlinearity, and the peculiarities of stochastic connections. The method consists of the following stages: collection of statistical data; calculation parameters in the mathematical model; evaluation of the values of the parameters; calculation of the input parameters. The mathematical model of the processing technology of the seed mass of vegetables and melons does not impose any restrictions on the properties of the random sequence of input and output parameters (linearity, stationarity, monotonicity, scalarity, etc.). It allows taking into account the features of seed processing and, as a result, achieving the maximum quality of separation of vegetable and melon seeds. The method has been approved on the basis of the experimental installation of a separating machine. The results of the experimental studies have confirmed the high accuracy of the suggested method. The application of the suggested models reduces the average error of determination of seed losses. Statistic data for calculating mathematical model parameters have been obtained in the course of processing melons and cucumbers on an experimental installation. The results of the experimental studies have confirmed the high accuracy of the suggested method.

A simple cage-autonomous method for the maintenance of the barrier status of germ-free mice during experimentation

The use of germ-free (GF) isolators for microbiome-related research is exponentially increasing, yet limited by its cost, isolator size and potential for trans-contamination. As such, current isolator technology is highly limiting to researchers engaged in short period experiments involving multiple mouse strains and employing a variety of mono-inoculated microorganisms. In this study, we evaluate the use of positive pressure Isocages as a solution for short period studies (days to 2–3 weeks) of experimentation with GF mice at multiple simultaneous conditions. We demonstrate that this new Isocage technology is cost-effective and room-sparing, and enables maintenance of multiple simultaneous groups of GF mice. Using this technology, transferring GF mice from isolators to Isocage racks for experimentation, where they are kept under fully germ-free conditions, enables parallel inoculation with different bacterial strains and simultaneous experimentation with multiple research conditions. Altogether, the new GF Isocage technology enables the expansion of GF capabilities in a safe and cost-effective manner that can facilitate the growth, elaboration and flexibility of microbiome research.