Browsing by Author "Tchaoushev S."

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    Mass transfer intensification in bioactive compounds recovery by alternative extraction methods: Effects of solvent
    (2019-02-01) Atanasov S.; Stoylov B.; Saykova I.; Tchaoushev S.
    Recently, the exploration of new alternatives to common organic solvents in combination with non-conventional energy sources is a subject of intense research and development as tools for green extraction of plant-derived natural products. This paper deals with the use of low frequency ultrasound (100 W, 32 kHz) and pulsed electrical fields (0.86 kV cm-1, 13 Hz) to raise the efficiency of the extraction of selected plant species rich in valuable phenolic compounds. Four types of natural deep eutectic solvents were applied for the ultrasound-assisted extraction of silymarin from milk thistle among which a choline-chloride-based mixture with glycerol was proved to be the most promising one. Additionally, the usage of high ultrasound power significantly increased the concentration of sylimarin as compared to traditional ethanol extraction, generating rapidly for 10 min considerable temperature rise as a side effect under non-cooling conditions. The application of PEF as a pre-treatment for 0.8 s to the extraction allowed reducing the ethanol percentage in the ethanol/water mixtures giving comparable phenolic yields, without any, or very little, increase in temperature. As such, optimized power intensity in conjunction with appropriate solvent system provides a potential to improve the release of thermally unstable bioactive compounds under mild processing conditions.
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    Modelling of a continuous process for a conversion of d-sorbitol to L-sorbose by gluconobacter oxydans
    (1991-01-01) Tchaoushev S.; Nicolov N.; Krysteva M.
    A mathematical model of a multistage bioreactor for continuous conversion of D-sorbitol to L-sorbose has been developed. The model solution presents possibility for determining the biomass concentration along the reactor height and the required number of stages for achievement of a given conversion rate. The mathematical model was tested on the basis of experimental data obtained in a laboratory glass reactor. The experimental conversion rate of D-sorbitol to L-sorbose rose to approximately 37% in the seconnd stage of the laboratory bioreactor. The value was in good agreement with the numerical results from the solution of the model. On the basis of these investigations it may be assumed that full conversion of D-sorbitol to L-sorbose should be obtained in bioreactor with 5-6 stages. © 1991 Taylor & Francis Group, LLC.
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    Spray pyrolysis equipment for various applications
    (2013-05-21) Kozhukharov S.; Tchaoushev S.
    The fabrication of all kinds of industrial products is based on the specific combination between the applied methods, and the conditions of syntheses (temperatures, pressures, flow rates and the chemical compositions of gaseous and liquid fluxes, etc.), resulting on the properties and performance of the obtained products. On the other hand, both the methods and the conditions for synthesis depend on the available equipment, which is able to supply suitable conditions for synthesis via Spray Pyrolysis (SP) and further treatments of the desired product. The present work is an attempt to summarize the basic types of equipment, and conditions for obtaining of products for various applications, via the spray pyrolysis method.