Том 10, № 2 (2020)
Chemical Sciences
Synthesis and structure of sodium 1-alkoxy-1,4-dioxo-2-alkenolates and bis-(4-alkyl(aryl)- 1-oxo-1-alkoxyalkane-2,4-dionato) metals (II) based on them
Аннотация
A priority task in contemporary organic chemistry consists in the synthesis of practically useful metal complexes having carbonyl-containing ligands. The present article details the isolation of several new bis-(4-alkyl(aryl)-1-oxo-1-alkoxyalkane-2,4-dionato) metals (II) via complex formation of metal salts of (zinc (II), copper (II) and nickel (II)) with sodium 1-alkoxy-1,4-dioxo-2-alkenolates obtained by condensation of alkyl (aryl) methyl ketones with dialkyl oxalates in the presence of sodium or sodium hydride as a condensing reagent. The structure of the synthesised sodium oxoenolates and metal complexes was confirmed by spectral analysis methods (IR, NMR 1H-, NMR 13C-spectroscopy and mass spectrometry). In the IR spectra of the solid samples of the isolated compounds, stretching vibrations bands of ester carbonyl groups were identified, as well as high-intensity ether bands due to the vibrations of С-О-С bonds. For compounds containing aromatic fragments, bands corresponding to vibrations of monosubstituted benzene rings were found in the IR spectra. The NMR spectra of 1H of sodium oxoenolates and metal complexes recorded in DMSO-d6 demonstrated characteristic signals of ethoxy and n-butoxy fragments, methine protons, as well as protons of aromatic rings. Chemical shifts of carbon atoms in the NMR spectra 13C of sodium oxoenolates correspond well to the reference values. In the mass spectra of synthesised compounds recorded in electrospray mode, signals of protonated and cationised molecules were observed [M+H]+, [M+NH4]+, [M+Na]+, [M+K]+. Using quantum chemical methods, the models of the obtained compounds were constructed along with a calculation of the formation energies and dissociation constants. Optimisation of the geometric parameters of the equilibrium states of sodium oxoenolate and metal complexes was carried out using the following two methods: density functional theory (DFT) and self-consistent field (SCF). The relative formation energies indicate high stability of the synthesised substances, while, according to the data obtained, copper complexes are characterised by greater stability in the gas phase as compared to zinc and nickel.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):180-187
180-187
Formation of humic substances in the reaction of D-glucose with p-toluidine in anhydrous ethanol
Аннотация
The aim of the study was to investigate the processes of formation and structural group composition of the products formed during the reaction of D-glucose with p-toluidine in anhydrous ethanol using electronic and vibrational spectroscopy methods. The evolution of the profiles of the electronic spectra of working solutions shows the formation of a chromophore system: clear peaks at 380 and 440 nm are already present at a reaction time of 60 min. The appearance of an additional maximum at 520 nm (90, 120 min) likely corresponds to the formation of chromophores in condensed structures, as confirmed by a decrease in the values of the E4/Е6 indices over time. The dynamics of the transformation of structural elements is also clearly seen in the analysis of IR spectra: as the reactions proceed, the CH aliphatic component of the structure decreases, while the aromatisation and functionalisation of products by chromophore groups increases. For products obtained between 90 and 120 min, a clear band at 1656 cm-1, attributed to stretching vibrations of multiple bonds in conjugated C=C–C=O systems and azomethine fragments, indicates the of condensation reactions. In the spectra of insoluble solid products fractionated by water, the intensity of the bands at 1656 and 1190 cm-1 is significantly reduced; this is possibly due to the transfer of some of the coloured low molecular weight products to the aqueous phase. A comparison of the IR Fourier transform spectra of the final solid products with the spectra of natural and synthetic humic-like substances indicates their similar structural group composition. The intensity of the bands at 1620, 1508 and 815 cm-1 indicates a significant contribution of the aromatic component to the structure of the products of water-insoluble fractions; the water-soluble fractions mainly include aliphatic oxygen-containing structures resulting from the oxidative destruction of the initial carbohydrate. The synthesised products seem promising as convenient plant growth regulators with controlled release of the active substance.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):188-195
188-195
Component complexation study of Ni(II) with 1,3-diphenyl-2-(2-hydroxy-4-nitrophenylhydrozo) propodion-1,3
Аннотация
The effect of various components, including α,α′-dipyridyl (α,α′-dip), phenanthroline (Phen) and bathophenanthroline (B-phen), on the complexation of Ni(II) with 1,3-diphenyl–2-(2-hydroxy-4-nitrophenylhydrozo)propodion-1,3 (R) was studied. Homogeneous (Ni(II)-R) and mixed-ligand (Ni(II)-R-α,α'- dip, Ni(II)-R-Phen and Ni(II)-R-B-phen) complex compounds are determined to form at pH = 6, 5.5 and 5, respectively. The yield of the Ni(II)-R complex is established to be maximal at R concentration of 8·10-5 M; Ni(II)-R-α,α'-dip – at concentration R and α,α'-dip of 8·10-5 and 5.2·10-5 M, respectively; Ni(II)-R-Phen – at concentration R and Phen of 8·10-5 and 4.8·10-5 M, respectively; Ni(II)-R-B-phen – at concentration of R and B-phen 8·10-5 and 4·10-5 M, respectively. All complexes, which differ in stability, were determined to form immediately after mixing the solutions of the components. The ratio of reacting components in the composition of homogeneous (1:2) and mixed (1:2:1) ligand compounds is established in terms of conformity to Beer's law. The equation coefficients for the calibration curve were obtained by the method of least squares. In the complexation of nickel(II), the А = f(c) dependence was shown to be expressed by linear equations. The stability constants of homogeneous (Ni(II)-R) and mixed-ligand (Ni(II)-R-α,α'-dip, Ni(II)-R-Phen and Ni(II)-R-B-phen) complexes were calculated. Under optimal complexation conditions, Ni(II)-R was titrated with a solution of the components, including α,α'-dip, Phen and B-phen, using the conductometric method. The effect of foreign ions on the complexation of nickel(II) with R both in the absence and presence of other components was studied. In the presence of other components, the selectivity of complexation reactions was established to increase significantly. These reagents were proved to be more selective for spectrophotometric determination of nickel(II) in comparison with reagents known from the literature. The developed technique was applied for nickel(II) determination in three varieties of apples.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):196-204
196-204
Impedance spectroscopy study of anticorrosive properties of epoxy compositions
Аннотация
Although metals and their alloys are important structural materials, electrochemical or chemical interactions between metal structures and the environment leads to their spontaneous destruction. In order to protect metal products from corrosion, epoxy resins and polymer composite materials can be applied. However, polymer-coated metals may degrade under operating conditions due to electrochemical reactions at the polymer-metal interface caused by water absorption and diffusion in epoxy coatings. The present study is aimed at an investigation of the anticorrosive behaviour characteristic of epoxy compositions following exposure to sulphuric acid. The method of impedance spectroscopy was applied to evaluate epoxy coatings on a steel base. The composition of the epoxy binder included bisphenol A resins cured with various amine curing agents. In order to identify structural changes in materials, as well as the changes in their protective properties, the effects of an aggressive environment were simulated by means of exposure to concentrated sulphuric acid over a 30-day period. Impedance hodographs of the studied systems were obtained and equivalent schemes for the approximation of experimental data proposed. The high porosity of the NPEK-114L based epoxy system was established to result in an increase in the corrosion rate. Dissolution of corrosion products over a longer test period – and consequent higher diffusion of corrosive ions in the coating – was determined to cause a decrease in corrosion resistance. Epoxy compositions based on NPEL-128 resin (oligomeric product based on diphenylolpropane diglycidyl ether) demonstrated improved anticorrosion characteristics. The addition of alkyl glycidyl ether for NPEK-114L resin viscosity reduction was shown to affect the protective properties of the composite under acid exposure.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):205-212
205-212
Study of buckwheat husk application for water demineralisation
Аннотация
In the present paper, a brief review of the scientific literature on the main research directions in the field of sorption filters used for water demineralisation is presented. Materials used for these purposes, both of mineral and organic origin, are considered. Various natural materials, including waste products from wood processing and agriculture, are promising raw materials for the production of sorbents. Since these materials are typically characterised by low sorption ability in their raw form, additional activation processes are required. In this connection, research was conducted by the authors on the sorption of hardness salts (calcium and magnesium) from aqueous solutions in static conditions using raw and chemically modified buckwheat husk in a concentration range from 2 to 40 mEq/dm3. Hydrochloric and phosphoric acids, as well as sodium hydroxide, were used as modifiers. A study of the sorption kinetics demonstrated that the system achieves equilibrium within 5 min from the start of sorption. Additionally, the possibility of maximum demineralisation of aqueous solutions was studied. The best sorption properties with respect to hardness salts were demonstrated by buckwheat husks modified by sodium hydroxide, which had a maximum sorption capacity of 2.4 mEq/dm3 as compared to 2.0 mEq/dm3 for raw husks. For all types of obtained materials, mineral sorption isotherms were constructed in the range of studied concentrations. These isotherms were established to be of S4 type according to the Giles classification. Mathematical processing was carried out according to the sorption models of Langmuir, Freundlich, BET and Dubinin-Radushkevich. The sorption process for calcium and magnesium cations was revealed to be most accurately described by the Freundlich equation.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):213-222
213-222
Physico-chemical biology
On aggregation in binary biopolymer systems
Аннотация
The main structural protein of the human eye, which accounts for about 50 % of the mass of all water-soluble proteins comprising the lens, is α-crystallin. Alpha-crystallin functions as a molecular chaperone, preventing other lens crystallins from interfering in the vital activity. Alpha-crystallins partially or fully stabilise unfolded proteins, preventing the formation of deposits, helping to preserve the lens transparency and reducing the risk of a number of diseases, including cataracts. This biological phenomenon can be considered in the framework of materials science when considering the problem of slowing down the aging processes of polymers. In the present study, methods for slowing down the process of aggregation of α-lactalbumin in solution are considered, using the binary system α-lactalbumin–αA-crystallin as an example. To this end, experimental data on the rate of change of the aggregation process were formalised, i.e. expressed in terms of transition temperatures and plasticisation functions of the components. The proposed expressions make it possible to clarify the concentration dependence of the initial aggregation rate, its order, and also to quantify the effect of the dose of UV irradiation on the aging process of the system. The experimentally obtained result means that an increase in the content of α-crystallin leads to an additional blocking of hydrogen bonds in the surface layers of α-lactalbumin and, accordingly, to an increase in the plasticising effect. In addition, the obtained expression of the activation energy of polymer chain rearrangement helps to account for the influence of infrared radiation on the development of so-called thermal cataracts (usually occurring in glassblowers, steelmakers, blacksmiths, welders, etc.), when the etiological factor consist in infrared rays having wavelengths from 0.74 to 2.50 microns, which freely pass through the cornea and iris without damaging them, and are largely adsorbed by the lens, causing its overheating.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):223-231
223-231
Phytate hydrolysing activity of the Aspergillus niger L-4 micromycete strain
Аннотация
The aim of the study was to study the phytase synthesis capability of Aspergillus niger L-4 strain. The method for determining phytase activity is based on establishing the content of inorganic phosphates as a result of the action of phytase on the substrate under certain standard conditions by binding them with a vanadium-molybdenum reagent to form a coloured complex. The use of phytases for the hydrolysis of phytates in animal feed is important from the point of view of preserving the environment: when phytate complexes are destroyed, phosphorus is released, which performs an important structural and regulatory function, ensuring the normal development of bone and dental tissues and supporting their safety and integrity. Phosphoric acid is involved in the synthesis of kinases responsible for the normal course of chemical reactions in cells, in fat metabolism, as well as in the synthesis and breakdown of starch and glycogen. This reduces the release of undigested phosphorus into the environment. The object of the study consisted of native solutions obtained by culturing an industrial strain of acid-forming A. niger L-4 on various carbohydrate-containing media. The A. niger L-4 strain, previously selected at the All-Russian Scientific Research Institute of Food Additives for fermentation of molasses, has the ability to synthesise extracellular phytase. This paper presents the results of studies of phytase activity during the cultivation of A. niger L-4 on carbohydrate-containing media. It was found that in order components of the sucrose-mineral medium provide an elevated level of low-molecular-weight sugars necessary for increasing the productivity of phytase biosynthesis. Phytase activity in the native solution was shown to increase over 72 hours of fermentation to reach a value of 25.8±0.1 units/cm3. The phytase activity was 1.5 times higher than the fermentation process of a corn starch hydrolysate with a dextrose equivalent DE = 21±1 %, ensuring the productive biosynthesis of citric acid.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):232-239
232-239
Search for biologically active substances of natural origin based on low-polar conifer extracts
Аннотация
In recent years, research interest in the application of biologically active substances as a means of increasing the yield and stability of agricultural plants has been increasing. The main advantages of natural substances, which determines the prospects of their application in contemporary agricultural technologies, are seen in terms of their environmental safety and multifunctionality of action, including the ability to reduce various environmental stresses on plants. For both economic and ecological reasons, one of the main sources of biologically active substances consists of coniferous trees. Thus, an important task is presented in the search for new compounds from coniferous trees having growth-regulating and stress-protective properties as applied to various plants of commercial interest. In order to solve this problem, the growth-modulating and anti-stress biological activity of eight extracts containing compounds from needles and branches of three low-polar pine species (Pinus gen.) was tested using a model based on the Arabidopsis (thale cress) root and leaf rosette growth indicator. The obtained data confirmed the possibility of using the studied plant model for identifying the biological activity of low-polar metabolite extracts. Growth inhibition of the Arabidopsis main root, lateral roots and leaf rosettes by extracts and fractions of low-polar substances of the Pinus coniferous trees was demonstrated. The most significant growth inhibition of the main root was characteristic of the P. koraiensis (NIOC-28/1) needle hexane extract, while the neutral substances of the P. sibirica (NIOC-32/1) needle hexane extract suppressed the growth of both the main and accessory roots. The demonstrated allelopathic growth inhibition for Arabidopsis roots and leaf rosettes caused by extracts and fractions of low-polar substances of the Pinus coniferous trees shows the relevance of further study into the most active extracts for their possible application as herbicides. The absence of a positive effect for the studied extracts on the growth stability of the Arabidopsis root to heat shock was established.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):240-250
240-250
Effect of enzyme preparations on the aroma-forming components of red table wines
Аннотация
The present study was focused at the effect of enzyme preparations applied in winemaking on the concentration of aroma-forming components. In this study, the application of enzyme preparations – including trenolin rouge, trenolin rote, laffasa 60, lafazyme extract and extrazyme terroir – was shown to cause a change in the concentration of aldehydes, esters, higher alcohols, ketones, acids and terpene compounds in comparison with a control sample of wine produced by classic technology. The greatest amount of acetaldehyde and ketones was detected in table wines produced using enzyme preparations of lafazyme extract, laffasa 60 and extrazyme terroir. The introduction of enzyme preparations into the grape pulp contributed to the decomposition of the norizoprenoid and carbohydrate complex with the release of ionone and the appearance of violet and rose tones in the aroma and taste of wine (laffasa 60, extrazyme terroir, lafazyme extract). In the studied Cabernet-Sauvignon samples, the presence of various terpene compounds causing the formation of various flower (lilac, linden, acacia, jasmine) and citrus shades in wine was demonstrated. The application of enzyme preparations – in particular, laffasa and extrazyme terroir – resulted in an increase in the mass concentration of terpene compounds in comparison with the traditional technology, especially for linalool, geraniol, nerol, limonene, α-terpinolene and 3-hydroxy-β-damascone. No significant changes were observed in the mass concentration of higher alcohols against the background of decreased methanol concentration. A marked increase in the concentration of β-phenylethanol, phenolic acids (especially gallic and vanillic), as well as ethyl esters of caproic, caprylic, myristic, linoleic, stearic and pelargonic acids, was noted. Therefore, enzyme preparations – especially lafazyme extract, laffasa 60 and extrazyme terroir – are recommended in the production technology of red table wines in order to improve their aroma.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):251-260
251-260
Cellulose hydrolysis by Trichoderma viride enzyme complex in the presence of sodium fluoride: effect of substrate structure and cellulase sorption activity
Аннотация
The dependence of cellulase activity of the Trichoderma viride fungus on three factors – substrate type, enzyme sorption properties and sodium fluoride (NaF) concentration – was studied. The four studied water-insoluble substrates were based on two native (birch wood and wheat straw) and two model (microcrystalline cellulose and filter paper) materials. In addition, a water-soluble Na-carboxymethyl-cellulose substrate specific for endoglucanase activity was studied. The T. viride cellulase complex from the “Celloviridin G3x” preparation was separated into fractions differing in sorption properties using the affinity chromatography method. The cellulase activity of the initial complex and obtained fractions was measured with respect to all substrates at different concentrations of NaF ranging from 0 to 1000 mg/L. Qualitative differences in the protein composition of the preparation and fractions were studied by SDS electrophoresis. With the introduction of NaF (100–500 mg/L), the initial cellulase complex activity increased with respect to all substrates. The hydrolysis rate of model samples was observed to increase by up to 100 %. Comparison of chromatographic fraction activity relative to model substrates demonstrated the NaF to have the opposite effect on the catalytic and sorption properties of cellulases. The activity of high affinity fractions containing cellobiohydrolases and low molecular weight endoglucanases in the presence of fluoride decreased by 35–90 % in relation to all substrates. Although weakly adsorbing fractions (endoglucanases I, II + cellobiasis) under the same conditions were inhibited by 15–20 % with respect to cellulose with a high degree of crystallinity (MCC), these were activated 1.3–3 times slower with respect to a water-soluble substrate (Na-CMC) and a substrate with less crystallinity (filter paper). Thus, the total effect of fluorides on the enzymatic hydrolysis of the plant substrate is determined by the crystallinity degree of the cellulose substrate, as well as by the ratio of stronglyand weakly-sorbed components in the cellulase complex. Possible molecular mechanisms of these effects are additionally proposed.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):261-273
261-273
Effect of sodium salicylate treatment on physiological and biochemical parameters of wheat seedlings under the influence of heavy metals
Аннотация
The objective of this work was to study the effect of cadmium sulfate and zinc sulfate on the growth and development of common wheat plants (Triticum aestivum L.) of the Moskvich variety. In order to determine the physiological and biochemical parameters of seedlings and the possibility of regulating their resistance to the stress factor, preplanting treatment of seeds with sodium salicylate (СNa) was carried out. Wheat seeds had been germinating in a solution of 0.1 mM СNa for 3 days at a temperature of 21–23 ºС and under a 16-hour daily illumination of 3000 lux illuminance. On the 4th day, the seedlings were transferred to plastic containers, where they continued to grow in a climatic chamber under periodic irrigation with solutions of CdSO4 and ZnSO4 salts with a concentration of 10-6-10-3 M. On the 7th day of the experiment, the length and fresh weight of the root system and shoots of the seedlings were measured, alongside with the lipid peroxidation (LPO) activity and the enzyme activity superoxide dismutase (SOD) in the cells of the leaves, as well as the content of proline in the leaves and roots of wheat seedlings. It has been found that for establishing the differences in the effect of cadmium and zinc ions on wheat plants using only biometric indicators is not sufficient. In our studies, the determination of LPO activity and proline content served as an indicator of the development of oxidative stress in the cells of wheat seedlings under the influence of CdSO4 and ZnSO4. At the same salt concentrations, only CdSO4 contributed to increased LPO activity and the formation of proline, which could be a signal for triggering the protective reactions of the cell. The low SOD activity under these conditions is probably resulting from the fact that it is proline that reduces the formation of reactive oxygen species either by terminating the cascade of free radical reactions or by inhibiting the CdSO4 enzyme. ZnSO4 salt is less toxic, since in the same range of concentrations it does not cause an increase in the content of LPO and proline products. The influence of CNa on these parameters depended on the nature of the heavy metal and the strength of its action, and produced both pro- and antioxidant effects, both provoking oxidative stress or protecting against it.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):274-283
274-283
Obtaining of new organosilicon fertilisers and their testing via water stress modelling
Аннотация
Under adverse climatic conditions, plants are often exposed to abrupt changes that negatively impact on crop yields. In this connection, a promising direction for reducing the negative impact of abiotic factors on plants consists in the use of silicon preparations. The present study is aimed at the synthesis of organosilicon fertilisers for spring wheat plants and their testing by means of abiotic stress modelling. As the basis for the synthesis of new organosilicon fertilisers with protective properties, the multipurpose compost (KMN) and fermentation product (PF) developed at the All-Russia Research Institute of Reclaimed Lands were selected. New organosilicon fertilisers were obtained by adding sodium metasilicate in KMN and PF at the aging stage in amounts of 3 and 5 % mass. SiO2 respectively. The dissolution of metasilicate was accompanied by active processes of alkaline hydrolysis, ammonification and nitrification, resulting in the increased content of nitrates, humic acids and silicon compounds in the finished organosilicon fertilisers. The testing of the obtained fertilisers was carried out in a laboratory experiment by modelling water stresses (acute lack of moisture and excessive soil moisture) for spring wheat plants of the Irgina breed. In general, the most significant positive reaction of plants was observed for fertilisers containing 3 % mass. of SiO2. In the cases of treatment with new fertilisers, imitation of an acute lack of moisture led to the development of more powerful plants characterised by a slight change in the length of the seedlings against the background of a significant increase in their mass (on average, by 7–10 % relative to the initial PF and KMN not enriched in silicon). Modelling of excess soil moisture in these cases contributed to an increase in all biometric indicators by an average of 6–11 % relative to the initial PF and KMN. Consequently, the obtained organosilicon fertilisers were experimentally shown to reduce negative abiotic effects on plants.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):284-293
284-293
Effect of nodule and pathogenic bacteria on levels of nitric oxide and cyclic adenosine monophosphate in pea roots at initial stages of interaction
Аннотация
A significant role in the initial stages of rhizobial symbiosis formation in pea plants is performed by innate immunity. In this connection, the present study is focused on the concentration dynamics of two signalling molecules – nitric oxide (NO) and cyclic adenosine monophosphate (cAMP) – in the roots of etiolated seedlings of the Pisum sativum L. pea interacting with pathogenic (Pseudomonas syringae pv. Pisi) and nodule (Rhizobium leguminosarum bv. Viceae) bacteria. In time dynamics experiments, an endogenous rhythm of nitric oxide content changes in the root tissues of pea seedlings was characterised by an increase followed by a decrease in the level of nitric oxide and depending on exogenous biotic factors (symbiotic and pathogenic bacteria). Similar fluctuations were also observed when studying the dynamics of cyclic adenosine monophosphate concentration under the influence of the same biotic factors. The observed effects are assumed to be associated with certain exometabolites of Rhizobium leguminosarum bv. viceae (Nod-factors) and Pseudomonas syringae pv. pisi (cell wall exopolysaccharides) influencing the legume plant and activeting its innate immunity. Moreover, it is feasible that the different dynamics of changes in the studied components of the host plant signalling systems at the initial stages of interaction with symbiotic and pathogenic microorganisms have a variegated function: regulatory or protective in cases of symbiosis and pathogenesis, respectively. The observed change in the dynamics of the NO-synthase and adenylate cyclase signalling systems (NO and cAMP) components is assumed to be applied by the host plant as a “code” for transmitting a signal concerning the nature of the operating factor and the generation of corresponding reactions at the molecular level.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):294-302
294-302
Effect of the autohydrolytic treatment of Miscanthus sacchariflorus Andersson on the yield of the reducing substances during the subsequent fermentolysis
Аннотация
The effect of the autohydrolytic treatment of Miscanthus sacchariflorus Andersson on the yield of the reducing substances during the subsequent fermentolysis has been determined. It was established that a change in the conditions of the auto-hydrolytic treatment of Miscanthus sacchariflorus Andersson induces a formation of solid fractions containing cellulose, lignin, hemicellulose and mineral substances, the ratio of which depends on the severity factor, i.e. temperature and processing time. It was shown that at the severity factor of 5.67, almost complete hydrolysis of hemicellulose occurs, however, there is an increase in the lignin content in the solid fraction (up to 46.0 %) relative to the lignin content in the feedstock (20.8 %), which is due to lignin condensation with a consequent formation of pseudo lignin. The highest content of cellulose in the solid phase is observed as a result of hydrolytic processing of raw materials with a severity factor of 4.17 to 4.39, a temperature of 160 оС and a processing time of 25 min. At an increased temperature, an increase in the acidity of the medium catalyzes the hydrolysis of cellulose and reduces its content in the solid fraction to 60 % at a severity factor of 5.67. During the auto-hydrolytic treatment of Miscanthus sacchariflorus Andersson, an increase in the ash content in the solid fraction is observed. The solid fractions obtained after treatment with Miscanthus sacchariflorus Andersson were used as a substrate and were subjected to enzymatic hydrolysis with the enzyme preparations “Cellolux-A” and “BrewZime BGX” at an initial substrate concentration of 33 g/l. The increase in the yield of reducing substances has shown a steady increase with the removal of hemicelluloses and reached its maximum value (45.1 %) with an increase in the treatment severity factor to 4.48. The availability of the cellulose surface for the action of enzymes has decreased with an increase in the stiffness factor beyond a value of 4.48 due to the accumulation of lignin in the solid phase, as evidenced by a decrease in the yield of reducing substances in the enzyme to 31.8 %.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):303-313
303-313
The use of enzymatic modification in recycling of meat and bone collagen-containing byproducts
Аннотация
The objective of this research was to study the process of extraction of valuable protein watersoluble substances from highly mineralized meat and bone raw materials during hydrolysis by proteolytic enzymes. The experiments were carried out on beef tubular and costal bones using enzymes Alcalase 2.5 L, Protamex, Protosubtilin G3x. The efficiency of protein hydrolysis was evaluated by the accumulation of nonprotein amino nitrogen in the aqueous protein extract, the amount of which was determined by formol titration. The chemical composition of raw materials and hydrolysis products was evaluated by standard physicochemical methods. The drying of hydrolyzed protein fractions was carried out on a lyophilic freeze dryer at a condenser temperature of -55 ° C. Drying of the sedimentary protein-mineral fraction was carried out by convection method at 60 aboutC. The general chemical composition of raw materials and protein hydrolysates is established. It was shown that fermentolysis in an aqueous medium with preliminary separation of fat and subsequent separation of fractions makes it possible to obtain low molecular weight water-soluble peptides and protein-mineral insoluble compositions, as well as fat products in the amount of 13.3–14.4 % of raw materials by weight. The yield of proteins by the content of solid products in water-soluble freeze-dried products was 6.1–7.9 %, depending on the type of enzyme and hydrolysis conditions. The bulk of the raw material's protein mass is precipitated together with mineral substances during fermentolysis. The solids content in dense sediments was 66.5–73.8 %. It is recommended to use the fermentolysis of meat and bone raw materials for pre-treatment in subsequent high-temperature hydrolysis. Protein products obtained by enzymatic modification of meat and bone raw materials are recommended for use as part of feed supplements, microbiological media and fertilizers, as well as feed for aquaculture. To accomplish that, it is necessary to study their amino acid composition and conduct biological tests. The extracted fat may also serve as a raw material for a number of fat products (margarine, spreads, soap).
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):314-324
314-324
Chemical technology
Study of the filtering properties of fabrics derived from cotton and synthetic fibres
Аннотация
For the dehydration of various solutions and suspensions in the chemical industry, different types of filters are applied, including disk, cartridge, bag, press filters and others, with the main element consisting of a filtering membrane made of cotton or synthetic fibres. In this case, the main requirement for the membrane involves high retention ability with respect to the dispersed phase of solutions and suspensions. For application in forming a membrane, filter fabrics characterised by low clogging are advisable. In the present paper, the filtering properties of fabrics made of synthetic and cotton fibres are evaluated on the basis of experimental data along with a determination of indices of efficiency, turbidity, clogging and service life. The kinetics of the suspension dehydration was studied in a wide range of dispersed phase concentrations (3–500 g/dm3). The results of the studies revealed all tested samples of synthetic fabrics to exibit less clogging than the wide ly-used cotton ones (filter-diagonal and calico). The adhesion value of dispersed particles to the fibres of the membrane is established to allow the selection of appropriate fabrics for a particular filter type taking the acting direction of the driving force and gravity during the filtration process into account. The main phases of sediment formation on the membrane surface were established. The initial filter layer is shown to form during the first period, with the structure of this layer being determined by the density of the suspension. Filtration modes were investigated with the transition from sludge filtration to clogging observed in the range of 50–100 g/dm3, which corresponds to the transition mode.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):325-331
325-331
Preparation of diesel fuel blends and study of their physical properties
Аннотация
The aim of the present work was to synthesize biodiesel fuels from sunflower oil through a transesterification reaction in the presence of a novel catalytic system. Under the molar oil-to-methanol ratio of 1:3 and the temperature of 55 °C, the product yield was 83 %. Physical properties of the biodiesel and diesel fuels under study, as well as their blends containing 20 and 50 vol% of biodiesel fuel (B20 and B50), were investigated against ASTM standards. An increase in the proportion of biodiesel fuel increases both the density of the B20 and B50 blends, as well as their kinematic viscosity, which remains within the 2–5 mm2/s range at 40 °C thus meeting ASTM requirements. It is shown that the content of unsaturated compounds in the biodiesel blends altered within the range specified by ASTM. The flash temperature of the B20 and B50 biodiesel blends was shown to be higher than that of diesel fuel. This led to some deterioration in their flammability, at the same time as making the transportation and storage of these fuels safer. The sulphur content in the biodiesel blends under study decreased significantly with an increase in the biodiesel content: from 50 m.c. in diesel fuel up to 27 m.c. in the B50 blend. The use of such biodiesel blends reduces the content of sulphur oxides in exhaust gases, which has a beneficial effect on the environment and human health. The use of the proposed catalytic system reduces the amount of foam produced by biodiesel washing, thus simplifying its synthesis. Due to the absence of the neutralization stage, the described catalytic system can be reused after water removal through distillation.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):332-338
332-338
Catalytic deparaffinization of middle distillates
Аннотация
The middle distillate fractions obtained in primary oil refining plants contain a significant amount of n-paraffins, which have positive pour points, resulting in degradation of the low-temperature characteristics of fuels produced from these fractions. To improve the low-temperature properties of middle distillate fractions, various depressor additives are used or dewaxing is carried out in various ways. The most efficient dewaxing process is the catalytic one. Classical methods for the secondary processing of hydrocarbon fractions are costly and often uneconomical for small oil refineries. The development of secondary hydrocarbon processing methods applicable at medium and low capacity refineries is an urgent task today. Therefore, our goal was to develop a technology for combined processes of primary distillation of oil coming through the Eastern Siberia – Pacific Ocean oil pipeline system and catalytic dewaxing of the resulting middle distillates. To determine the conditions for carrying out the process of catalytic hydrogen-free dewaxing, an experimental plant of continuous operation was developed with a feed rate of 10 l/h, including a tube furnace, a reactor with a fixed catalyst bed, a heat exchanger, and control and measuring devices. Experiments performed on a pilot plant made it possible to determine the optimal technological parameters for the catalytic dewaxing of middle distillates. It was shown that the catalytic dewaxing of middle distillates under experimentally determined conditions proceeds quite effectively on cracking catalysts SGK-1, SGK-5, KN-30-BIMT, manufactured in Russia. An optimal technological scheme for combining the process of primary oil separation and catalytic dewaxing of middle distillates is proposed. Calculation and optimization of the proposed technological scheme was performed in a computer simulation system ChemCad.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):349-359
349-359
Analysis of the products of low-temperature microwave pyrolysis of peat
Аннотация
To increase the efficiency and intensity of processing of organic natural caustobiolite or peat, a prototype laboratory microwave reactor with an increased loading volume of the processed material has been developed. The modernized experimental setup is a microwave reactor under reduced pressure with a constant removal of pyrolysis gases through a trap with liquid nitrogen into a gas sampler. The increase in the volume of the microwave reactor was achieved through the use of additional systems for transporting microwave radiation and a special system of absorption of reflected power from the reactor volume. The reactor was connected to a microwave source (industrial magnetron) with a frequency of 2.45 GHz, with a total power of 1 kW. The duration of microwave irradiation of peat in the reactor was 16 minutes. As a result of a series of experiments, samples of three fractions – solid, liquid, and gaseous – were obtained and analyzed. A comparative analysis of the products of low-temperature pyrolysis of bog sphagnum peat obtained by heating based on heat transfer from the walls of the reactor (conventional thermal heating) and heating by microwave radiation. The main difference between heating by radiation and heat transfer is that in the first case there is an increase in temperature throughout the volume, and not just in the zone of the phase boundary, which increases the intensification and the efficiency of the process. This is especially evident when heating solid objects in which there is no heat transfer by convection. Comparison of the products of the three fractions obtained was carried out using gas chromatography analysis data with massspectrometric detection, as well as using the results of elemental analysis. The study has shown that microwave heating causes a deeper destruction of the initial substrate – to the carbon residue and low molecular weight products of inorganic and organic nature. In addition, the surface of the solid fraction was examined using a scanning electron microscope; the presence of porous structures with pore sizes from 5 to 7 μm has been detected.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):339-348
339-348
Brief communication
Effect of zeolite content on proton conductivity and technical characteristics of the membranes based on crosslinked polyvinyl alcohol
Аннотация
Polyvinyl alcohol (PVA)-based ion-exchange membranes are a promising group of materials for use in solid polymer fuel cells (SPFC) due to their high hydrophilicity, film forming ability, low cost, good mechanical properties and the possibility of crosslinking PVA with various chemicals. The compounds with a carboxyl or carbonyl functional group, such as polybasic acids and their anhydrides, were used as crosslinking agents resulting in the formation of a gel. Cross-linking reagents may contain ionic groups, for example, sulfonic, inducing the proton conductivity of PVA in membranes. Ceramic materials based on the oxides of aluminum, silicon, titanium, tin, zirconium, etc. serve as dopants in order to improve the technical characteristics of such membranes, such as to increase ionic conductivity, chemical and thermal stability, as well as the mechanical strength of the membranes. In this work, we report on the preparation of new biodegradable proton exchange membranes for SPFCs based on of polyvinyl alcohol crosslinked with sulfosuccinic acid and doped with beta zeolite particles. The content of zeolite in the composition of the membranes was varied from 1 to 25 %. The effect of the zeolite content on proton conductivity, ion-exchange capacity, moisture content, swelling coefficient, fuel (methanol) permeability and mechanical properties of membranes was studied. An increase in zeolite content from 1 to 25 % leads to an increase in the ion-exchange capacity of membranes from 1.5 to 2.9 mmol/g, a decrease in moisture content from 38 to 28 % and a methanol permeability from 2.2710-6 to 6.9110-7 cm2 s-1. The temperature dependence of the proton conductivity of composite membranes in the range from 30 to 80 ºC at the relative humidity of 100 % was studied. The highest value of electrical conductivity was demonstrated by a membrane containing 25 % of BEA zeolite, whose proton conductivity was 23.2 mS·cm-1.
Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya. 2020;10(2):360-367
360-367