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Belyaev A.P.,St Petersburg State Chemical And Pharmaceutical Academy | Rubets V.P.,Saint Petersburg State University | Antipov V.V.,Saint Petersburg State University | Bordei N.S.,St Petersburg State Chemical And Pharmaceutical Academy
Russian Journal of Physical Chemistry A | Year: 2015

The results from structural and thermal studies on the formation of molecular crystals during the vacuum sublimation of paracetamol from its vapor phase are given. It is established that the vapor-crystal phase transition proceeds in a complicated way as the superposition of two phase transitions: a first-order phase transition with a change in density, and a second-order phase transition with a change in ordering. It is shown that the latter is a smeared phase transition that proceeds with the formation of a pretransitional phase that is irreversibly dissipated during phase transformation, leading to the formation of crystals of the rhombic syngony. Data from differential scanning calorimetry and X-ray diffraction analysis are presented along with microphotographs. © 2015 Pleiades Publishing, Ltd.

Alekseev K.V.,St Petersburg State Chemical And Pharmaceutical Academy | Dubina M.V.,St Petersburg Academic University | Komov V.P.,St Petersburg State Chemical And Pharmaceutical Academy
Applied Biochemistry and Microbiology | Year: 2015

The article discusses recent advances in the study of the metabolism of Aspergillus niger, a producer of citric acid, and some of its characteristics that may be responsible for the overproduction of citric acid. The paper is designed so that the entire process of citrate biosynthesis, from the absorption of glucose from a nutrient medium to the extraction of citric acid from cells, is divided into stages that are critical for the yield of the desired product. This arrangement of the material makes it possible to show the main regulatory steps in the chain of citrate synthesis. Influencing these steps enables regulation of the biosynthesis of citric acid at the level of cellular metabolism. This eventually opens promising avenues in the improvement of producing strains by means of genetic engineering. The paper also reviews the influence of some fermentation conditions (medium components, additives, and technological parameters) on metabolic processes in producing cells, which is important for an integral understanding of both biosynthesis process at the cellular level and fermentation technology. © 2015, Pleiades Publishing, Inc.

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