Microsoft Word - 9 SHEVCHENKO_final.doc 192 Journal homepage: www.fia.usv.ro/fiajournal Journal of Faculty of Food Engineering, Ştefan cel Mare University of Suceava, Romania Volume XVII, Issue 2 - 2018, pag. 192 - 196 DESATURATION OF CULTURAL MEDIA IN PROCESSES OF ANAEROBIC FERMENTATION *Olexandr SHEVCHENKO1, Anatoliy SOKOLENKO2, Konstantin VASYLKIVSKY2, Oleg STEPANETS2 1 Department of Processes and Apparatus for Food Production, National University of Food Technologies 2 Department of Mechatronics and Packaging Machinery, National University of Food Technologies Volodymyrska str. 68, Kyiv, Ukraine, 01601, tmipt@ukr.net, * Corresponding author Received 5th February 2018, accepted 19th June 2018 Abstract: The article deals with the analysis of transients in gas-liquid media with the self-synthesis of the gas phase. It is shown that the restriction of the mass transfer intensity in the culture media of the alcoholic and brewing industries is accompanied by the presence of transients in the state of saturation on СО2. It is determined that the level of carbon dioxide accumulation increases due to physical and hydrostatic pressures and the latter one is determined by the geometrical parameters of fermentation vehicles, but the quantitative desaturation per unit volume of the medium does not depend on hydrostatic pressure. Quantitative desaturation of CO2 depends on the pressure differences in the ingenious volume. It is shown that the restoration of the sorption properties of the liquid phase is possible due to combinations of reduction and subsequent increase of physical pressure. The analytical dependences on determination of interconnections of physical parameters in digestible media are given. Keywords: desaturation, gas-liquid medium, gas-retaining ability, mass transfer, hydrostatic pressure, solubility. 1. Introduction Formulation of the problem. Anaerobic fermentation of sugar-bearing media under the action of yeast cells is accompanied by the formation of a new cellular substance, the acceptance and assimilation of substances from the external medium, the splitting and removal of unnecessary and harmful compounds and the transport of substances within the cell. The energy supply of the processes is achieved thanks to the breath that begins with the splitting of glucose. The result of such transformation is the accumulation of ethanol and carbon dioxide in the medium. The presence of ethanol and carbon dioxide is accompanied by an increasing osmotic pressure, which ultimately limits the concentration of ethanol in the range of 8 ... 10% and a maximum of 12% with the use of osmophilic yeast [1-3]. Traditionally, these restrictions are associated with ethanol and its osmotic pressure, and the presence of dissolved CO2 in the fermented medium is an additive part [4]. In accordance with the Van-Hoff law and based on the principle of superposition [5], the total osmotic pressure of dissolved substances in the medium is determined by the dependence:       V RT M tm M tm M tm CO CO al al s s оsm          2 2 , where  tms ,  tmal and  tmСО2 , - mass of sugar, alcohol and carbon dioxide respectively as a function of time t; sM , Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava Volume XVII, Issue 2 – 2018 Olexandr SHEVCHENKO, Anatoliy SOKOLENKO, Konstantin VASYLKIVSKY, Oleg STEPANETS, Desaturation of cultural media in processes of anaerobic fermentation, Food and Environment Safety, Volume XVII, Issue 2 – 2018, pag. 192 – 196 193 alM and 2COM - the molecular masses of substances respectively in volume V of the solution; R - universal gas constant, J / (mol*K); T - absolute temperature, K At the end of fermentation when   0еі tm , we have:     V RT M tM M tm CO eCO al еal osm          2 2 , where еt is the final time of the process;  еCO tM 2 - the final mean of the solution of carbon dioxide, due to the presence of hydrostatic pressure. Calculations show that for alcoholic fermentation, 12% alcohol solution at a temperature T = 303 K creates an osmotic pressure of 6.58 MPa, while 2% solution of carbon dioxide leads to a similar index of 1.07 MPa. For the close values of the molecular weights (46 and 44, respectively), the final difference in osmotic pressure is explained by the limited solubility of CO2 in accordance with Henry's law, which is reflected by the equation of the material balance:  2СОals mmm , by which the main part of carbon dioxide is removed in the form of a dispersed gas phase. The formation of the latter begins when the concentration of CO2 reaches saturation constant sс : kPсs  where k is the Henry’s constant, depending on the nature of the gas and liquid phases and the temperature of the medium; P - partial pressure of the gas phase. Under the condition of anaerobic fermentation, the partial pressure is equal to the physical pressure. The latter means the presence of a concentration gradient in connection with hydrostatic pressure. By endogenous processes of synthesis of ethanol and carbon dioxide there are opposite transport flows on the interfacial surface of microorganisms and fluid medium. When there is unbounded solubility of OHHC 52 in water, the saturation of the medium on CO2 creates a barrier to mass return and the preconditions for the formation of gas microbubbles. The resistance to the mass transfer in a liquid film at the interface between the liquid and gas phases for the limited soluble gases is the main component [6, 10], and this hypothesis is hypothetically transferred to the surface "cell-medium". Transport of CO2 through the cytoplasmic and external shell has its own peculiarities and is carried out at the molecular level. At the same level, the penetration through the liquid film into the liquid phase is carried out. At the same time, the state of saturation of the medium is the reason of the resistance to mass transfer and its termination under certain conditions. The course of processes of anaerobic fermentation leads to the conclusion that the state of the liquid phase of the medium is noticeably close to the full saturation and depends on its hydrodynamic state due to the interaction of the dispersed gas and liquid phases. In this case, there is the effect of pressure in the volume of the gas phase, the geometry of the equipment, the hydrostatic pressure, the gas-holding capacity and the intensity of the circulating contours. The purpose of this study is related to the theoretical search for the mutual influence of these parameters for the restoration of sorption properties of culture media due to their forced desaturation. 2. Materials and methods Theoretical studies and phenomenological conclosions are performed on the basis of laws and principles that are involved in the interaction of chemical and biological processes of gas and liquid phases during Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava Volume XVII, Issue 2 – 2018 Olexandr SHEVCHENKO, Anatoliy SOKOLENKO, Konstantin VASYLKIVSKY, Oleg STEPANETS, Desaturation of cultural media in processes of anaerobic fermentation, Food and Environment Safety, Volume XVII, Issue 2 – 2018, pag. 192 – 196 194 anaerobic fermentation. They include material and energy balances, Pascal and Archimedes laws, laws of the continuity of flows, Henry, Van-Hoff [5], Gay-Lussac laws and Le Chatelier principle, principles of superposition and the most probable state [7]. The solution of the problem of restoring the sorption properties of culture media in CO2 is proposed on the basis of variable pressures [8–9]. 3. Results and discussion It is known that the ratio of material flows in the processes of fermentation is determined on the basis of the Gay-Lussac equation in the form: 88 2 92 2 180 2526126 COOHHCOHC  Let the concentration of dissolved glucose be 160 kg / m3 at the initial fermentation condition, then the total cycle of synthesized CO2 is 78.2 kg and ethyl – 81.8 kg. In recalculation on the number of moles of CO2 we receive: 3.1777 44 78200 2 СОМ mol under normal conditions, the volume of gas is: 3.43 10 293314.83.1777 5 2    P RTM V CO m3, and the average rate of synthesis of CO2 is: 086.1 72 2.782.782  е СО tdt dМ kg/(hour.m. It is obvious that in the regimes of the lag phase and the digestion, the rate of synthesis is considerably smaller and the state of saturation on СО2 is initially achieved on areas with lower hydrostatic pressure with a gradual transition to the full volume. From the beginning of the formation of the dispersed gas phase, it begins transition into a superficial volume of the gas phase with increasing pressure. Let’s assume that this pressure in the sealed volume increases from 0.1 to 0.2 MPa, and the increase of saturation constant sс at a temperature of the culture medium of 30 ° C is 1.48 kg / m3 or in moles is 1480: 44 = 33.64 This process is responsible for the areas A-B on the isotherm (Fig. 1). Forced pressure decrease from 0.2 to 0.1 MPa is accompanied by the release of 1.48 kg of CO2 from each cubic metric of the liquid phase, regardless of the value of hydrostatic pressure, since the dependence  Рсс ss  is linear. To achieve the desired level of desaturation of the medium in the ingenious gas phase, a pressure of 0.1 MPa is maintained, and it means that the desaturated CO2 is taken back from the apparatus (under normal conditions) in volume: 309.0 10 29314.364.33 52   СОV m 3/(m3 of the medium). The transition from 2sс to 1sс occurs without going beyond the saturation state, but its positive effect relates to a sharp increase in gas-holding capacity, an increase in the volume of the gas-liquid system and an increase in the dynamics of the hydrodynamic regime. Fig. 1. Schedule of dependencies sс  Рсs in isothermal processes t1 t2 t3 0 Р1 P2 P cs А В cs2 cs1 Δ с s Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava Volume XVII, Issue 2 – 2018 Olexandr SHEVCHENKO, Anatoliy SOKOLENKO, Konstantin VASYLKIVSKY, Oleg STEPANETS, Desaturation of cultural media in processes of anaerobic fermentation, Food and Environment Safety, Volume XVII, Issue 2 – 2018, pag. 192 – 196 195 The short-term flow of such transient processes with intensive mass transfer leads the media to the indicator 1sс . At the same time, in an ingenious volume at a pressure of 0.1 MPa the amount of carbon dioxide that remains will be: ingenious2 VМ СО  , where ρ is the specific mass of СО2, kg / m3, which is in moles   ingenious ingenious 3 73.22 44 10 2 V V М пСО    At the average rate of synthesis of CO2 086.1 2 СОМ kg/m 3, the recovery of the pressure at 0.2 MPa in the gravity process is achieved in time: 363.1 086.1 48.1 еt hours In this mode, the liquid phase is in saturation, and the dynamics of increase in pressure is reflected by the dependence:     ingenious ingenious73.2244 2 V RTV tM tР CO і          where  tM CO2 is the amount of synthesized CO2 in the function of time. At the same time with the pressure the constant of saturation increases from 1sс to 2sс :                            gH V RTV tM ktkPс CO iі   ingenious ingenious n 73.22 44 2 where H is the fluid value of the altitude coordinate in terms of the liquid phase. At constant rate of formation of СО2 const dt dМ СО 2 we have a linear accumulation law: t dt dМ М СОСО 2 2  . Under these conditions, the pressure change is reflected by the linear law (Fig. 2). It is important that at the same time, the liquid phase both for the reduction of pressure and its growth is in a state of saturation, which limits the intensity of mass transfer and the final level of accumulation of alcohol. The solution of the problem will be restoring the sorption possibilities of the culture medium due to the rapid increase in pressure in the ingenious volume after the completion of the desaturation phase. Such transition leads the system to a state when the fluid concentration of dissolved carbon dioxide is iс ( 2si cc  ). It is obvious that the fluid concentration is a function of time  tсс іi  and during the second phase it is reaching the value 2si cc  . The fulfillment of this condition means the necessity of another reduction of pressure in the system to a magnitude P1. The control over phases is monitored by the values of pressure P1 and P2 with the phase at the point A at the pressure P1 to complete degassing. 4. Conclusion The analysis of the transition processes in the gas-liquid media with the self-synthesis of the gas phase allows drawing the following conclusions: Fig.2. Graphic dependence of the pressure change in the ingenious volume Рі М (t) СО2 22.73ρRT Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava Volume XVII, Issue 2 – 2018 Olexandr SHEVCHENKO, Anatoliy SOKOLENKO, Konstantin VASYLKIVSKY, Oleg STEPANETS, Desaturation of cultural media in processes of anaerobic fermentation, Food and Environment Safety, Volume XVII, Issue 2 – 2018, pag. 192 – 196 196 1. Modern technologies of anaerobic fermentation of alcohol and brewing fields are accompanied by the presence of digestible media in conditions which are close to their saturation states on СО2. The latter limits the intensity of the mass transfer of carbon dioxide on the surfaces of the phase separation and the final result of the accumulation of ethyl alcohol in the alcohol industry. 2. Hydrodynamic modes in the media depend on the gas-holding ability, which in other equal conditions is determined by the ratios of the geometric parameters of the apparatus and media respectively. 3. The levels of CO2 accumulation increase due to hydrostatic pressures, but the quantitative desaturation from the unit of the volume does not depend on hydrostatic pressure, but it depends on pressure differences (P2 to P1). 4. Restoration of the sorption properties of the culture media is possible only with combinations of sharp reduction in pressure and subsequent increases in pressures in the gas ingenious volume. 5. References [1]. SHEVCHENKO O., SOKOLENKO A., VASYLKIVSKY K., VINNICHENKO I. The qualitative properties of culture media, Scientific works of the National University of Food Technologies, 23(2): 131–139, (2017). [2]. SHIYAN P., SOSNYTSKY V., OLIYNYCHUK S. Innovative Technologies of the Alcohol Industry. Theory and Practice, Askania, Kyiv, (2009). [3]. SHEVCHENKO O., VYNNYCHENKO I., STEPANETS A., BOYKO O. Features of transformations of material and energy flows in fermentation media, Scientific works of National University of Food Technologies, 23(3): 107–115, (2017). [4]. SOKOLENKO A., SHEVCHENKO O., MAKCYMENKO I. Osmotic pressure in fermentation media technologies, Ukrainian Food Journal, 6(1): 134–140, (2017). [5]. 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