Bio-based succinate is still a matter of special emphasis in biotechnology and adjacent research areas. The vast majority of natural and engineered producers are bacterial strains that accumulate succinate under anaerobic conditions. Recently, we succeeded in obtaining an aerobic yeast strain capable of producing succinic acid at low pH. Herein, we discuss some difficulties and advantages of microbial pathways producing "succinic acid" rather than "succinate." It was concluded that the peculiar properties of the constructed yeast strain could be clarified in view of a distorted energy balance. There is evidence that in an acidic environment, the majority of the cellular energy available as ATP will be spent for proton and anion efflux. The decreased ATP:ADP ratio could essentially reduce the growth rate or even completely inhibit growth. In the same way, the preference of this elaborated strain for certain carbon sources could be explained in terms of energy balance. Nevertheless, the opportunity to exclude alkali and mineral acid waste from microbial succinate production seems environmentally friendly and cost-effective.
To date, antibiotics are often used in the treatment of infectious diseases in medicine and veterinary medicine, as well as growth promoters in animal husbandry. The uncontrolled use of antibiotics leads to antibiotic residues in food products that are easily transmitted to humans through food chains. Due to these undesirable effects, as well as in connection with the circulation of substandard and counterfeit medicinal products, it is necessary to control the quality of medicinal products, as well as monitor the food safety of animal products by determining the content of drug residues using reference materials (RMs).The aim of this research was to develop a CRM for the composition of tylosin tartrate.In the course of the research, a method for preparing the initial RM was tested and successfully implemented, a critical analysis of methods for measuring the content of tylosin tartrate was carried out, and the choice of the HPLC method as the main method for quantitative determination of the certified value of the measured quantity (mass fraction of tylosin) was justified. The disadvantages of the microbiological method and the titrimetry method as alternative methods were shown. In accordance with RMG 93–2015 and GOST ISO Guide 35–2015, the standard uncertainty of the RM certified value from the characterization method, heterogeneity and instability of the material was estimated. The expanded uncertainty of the certified value was calculated. The result of the work performed was the approval of a new type of the CRM for the composition of tylosin tartrate GSO 11632 2020.Normalized metrological characteristics: the mass fraction of tylosin is 800–1100 µg/mg, the relative expanded uncertainty at k = 2, P= 0.95 is 6%. The CRM is stored in sealed ampoules separately from food and feed in a dry and dark place at a temperature from plus 4 °C to minus 18 °C, the shelf life of the CRM is 4 years.The practical significance of the results obtained makes it possible to expand the possibility of certification of measurement methods and control of the accuracy of the measurement results of the mass fraction of tylosin in veterinary medicinal products, food and food raw materials, animal feed, and environmental objects. The CRM can also be used to identify tylosin in medicinal products and to determine the susceptibility of pathogens to tylosin.
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