Objectives. Due to the complexity of their behavior, chemical process flowsheets are characterized by steady state multiplicity, in other words, the presence of multiple steady state operating modes having the same set of parameters. The steady states differ from each other in terms of their reagent conversion, selectivity, product flow composition, and stability. Therefore, in order to be able to identify the steady state having optimal technological indicators, the objective of searching all steady states of a chemical process flowsheet is relevant. The aim of the study is to research all possible steady states for a continuous stirred tank reactor (CTSR) according to the exothermic dimerization reaction and investigate the influence of different operation parameters on the technological indicators of found states.

Methods. Mathematical simulations of material and energy balance equations for reactor were used. The quantity of steady states was estimated by the number of energy balance discrepancy function intersection with the Ox axis. The Newton method in Microsoft Excel was used to solve nonlinear material balance equations of the reactor. The initial value of productivity was in range from zero to feed rate value of reagent of 100 kmol/h.

Results. It is shown that up to three steady states may exist for the reactor in dependence on the reaction volume, composition, and temperature feed flow, as well as the heat carrier flow rate. The results of this study correspond with earlier obtained results, which were obtained for irreversible reactions in adiabatic conditions. These states differ in productivity, internal reactor temperature, and stability. Steady state stability analysis of small parameter deviations was carried out. The analysis demonstrated that real characteristic values are in all found steady states of the reactor. Therefore, no oscillations in stable steady states of reactor and asymptotical operating time dependencies are implemented.

Conclusions. The technique of steady state analysis of a continuous stirred tank reactor developed over the course of this study, which reveals all steady states of the reactor with heat exchange, can be used to perform steady state analysis of recycled chemical process flowsheets, including continuous stirred tank reactors and separation blocks.

Objectives. While the phenomenon of cavitation is of interest for treatment of hydrocarbon mixtures, in particular crude oil and petroleum products, the literature lacks a systematic approach to conducting such research. This gap stimulates the need for a more in-depth study of the influence of this physical effect on the characteristics and detailed hydrocarbon composition of petroleum feedstock. Thus, the present work set out to explore the influence of the conditions leading to cavitation on the physicochemical properties and hydrocarbon composition of crude oil and petroleum products.

Methods. The objects of the study were two crude oil samples and four straight-run fractions—gasoline, kerosene, diesel, and fuel oil—having different characteristics and hydrocarbon compositions. Cavitation treatment was carried out in a hydrodynamic mode using a Donor-2 apparatus within a range of pressure changes from 20 to 50 MPa. The number of treatment cycles was from 1 to 20. The density was determined by pycnometry using the refractive index, an Abbe refractometer, and the fractional composition or fraction yield, as well as by distillation at atmospheric or reduced pressure for light or dark petroleum products, respectively. The hydrocarbon composition of the gasoline fraction was determined by chromatography and mass spectrometry.

Results. Changes in the densities and fractional compositions of the objects of study following their treatment under various conditions were recorded. Particular attention was paid to the hydrocarbon composition of the gasoline fraction: an increase in the content of normal alkanes was shown to be due to an increase in the number of structures with shorter carbon chains in comparison with the components of raw materials not subjected to cavitation.

Conclusions. The results of the study of the effect of cavitation treatment of crude oil and its individual fractions on their physicochemical characteristics showed that the nature of the changes depends on the treatment conditions and the initial characteristics of the sample. It is suggested that cavitation treatment causes cracking and compaction processes. The possibility of cracking reactions was confirmed by chromatographic determination of the group hydrocarbon composition of the samples.

Objectives. The study set out to develop a stable lyophilized formulation of the monoclonal antibody Eculizumab, comprehensively characterize the resulting material, and assess its stability for qualifying it as a reference material. This involved developing a matching placebo formulation, determining the optimal lyophilization conditions, and conducting a rigorous stability study.

Methods. In the development of the formulation and lyophilization conditions for Eculizumab, we tested various buffer systems and cryoprotectants. The residual moisture content in the resulting lyophilized samples was determined by Karl Fischer titration. Peptide mapping was performed using reversed-phase high-performance liquid chromatography (RP-HPLC) following enzymatic hydrolysis with trypsin. The structural, physicochemical, and biological properties were analyzed using various analytical methods, including RP-HPLC, high-performance liquid chromatography mass spectrometry, capillary sodium dodecyl sulfate electrophoresis, size-exclusion high-performance liquid chromatography, and enzyme-linked immunosorbent assay.

Results. A placebo solution for lyophilization of Eculizumab was selected with the following composition: 20 mM sodium phosphate, 4% trehalose, 0.2% polysorbate 80, pH 7.0. The results demonstrated a high degree of similarity between the candidate reference material and Eculizumab EU. Stability studies under storage conditions at 2–8°C demonstrated the material’s stability for one year, with control points at 3, 6, 9, and 12 months.

Conclusions. The absence of any effect of the drying process on the primary and spatial structure, post-translational modifications, content of related impurities, composition of isoforms, and specific activity was confirmed. Furthermore, stability studies demonstrated no significant changes in protein quality during storage at 2–8°C for at least 12 months, which represents the entire available data period at the time of manuscript preparation. The results indicate that the developed lyophilized material is a viable candidate for an international reference material, although its official qualification would require additional collaborative trials and long-term stability data.

Objectives. Soy protein hydrolysates are now widely used in the food industry, fish farming, poultry farming, livestock farming, as well as in medical preparations. The most effective method for their production is enzymatic hydrolysis. However, even with optimal proteolysis parameters, it is not always possible to achieve the required degree of hydrolysis. For this reason, various technological approaches are used to more intensively break down soy proteins, including the addition of enzyme preparations and pretreatment of the protein substrate. β-Conglycinin, one of the main soy proteins, is a glycoprotein whose carbohydrate portion consists primarily of mannose residues. We hypothesize that deglycosylation of β-conglycinin by an enzyme preparation with mannanase activity as a pretreatment of the soy substrate will lead to change in the structure of its protein portion due to the destruction of the carbohydrate component to increase the accessibility of peptide bonds to proteolytic enzymes. Thus, the work sets out to study the effect of enzymatic deglycosylation on the efficiency of soy protein hydrolysis.

Methods. Deglycosylation of β-conglycinin, hydrolysis of polysaccharides and lipids were performed by the Complex-concentrate enzyme preparation (Ferment, Republic of Belarus). Protein hydrolysis was carried out by the Protozyme C330 enzyme preparation (Ferment, Republic of Belarus). The formation of reducing sugars was confirmed by the Miller method. The degree of protein hydrolysis was determined by the pH-stat method. The molecular weight distribution of peptide fractions was analyzed by low-pressure liquid gel chromatography on a column with Sephadex^® G-50 Medium. Computer processing of the elution profile of peptide fractions was performed in the OriginPro 8.5.1 program using the Gauss function.

Results. It is established that the treatment of soy flour by the Complex-concentrate enzyme preparation (enzyme-substrate ratio 1 : 40, hydromodule 1 : 10) promotes the breakdown of both free oligo- and polysaccharides, as well as the carbohydrate component β-conglycinin. Proteolysis by the Protozyme C330 enzyme preparation (enzyme-substrate ratio 1 : 20, pH 7.5, 50°C, 3.5 h) carried out following 20 h of deglycosylation results in a product with a degree of hydrolysis of 56.3%. The content of low-molecular-weight peptides in soy hydrolysate is 83.9%. Proteolysis without enzymatic destruction of the carbohydrate part of β-conglycinin is shown to be characterized by a degree of hydrolysis of 9.2%.

Conclusions. A pretreatment approach involving deglycosylation of enzymatic β-conglycinin can be used to significantly increase the degree of hydrolysis of soy proteins.

Objectives. The work set out to develop a chromatographic purification technology for drugs based on modified single-domain antibodies specific to the SARS-CoV-2 virus, as well as to select the optimal parameters for the purification process and scale up this technology for production.

Methods. The study was conducted on a culture of Chinese hamster ovary (CHO) cells GAMP2C5  clone 78, CHO B5 clone 4, and CHO B10 clone 4, which were used to produce modified single-domain antibodies GAMP2C5, GAMB5, and GAMB10, respectively. Chromatographic purification was performed using AKTA pure 25 and AKTA Pilot 600s chromatographs. Quality control of the obtained drugs was carried out using high-performance liquid chromatography, capillary gel electrophoresis, dynamic light scattering, enzymelinked immunosorbent assay, and polymerase chain reaction.

Results. Multimodal chromatography using CA⁺⁺Pure-HA (TOSOH, Japan) resin based on type 1 ceramic hydroxyapatite can be effectively used for the removal of aggregated antibody forms. The drugs obtained after chromatography using CA⁺⁺Pure-HA resin based on type 1 ceramic hydroxyapatite have a purity of more than 97%. The developed purification technology was scaled up to purify 200 L of culture fluid after cultivation in an STR 200 bioreactor.

Conclusions. The described technology developed for purifying modified mono-domain antibodies using the CA⁺⁺Pure-HA multimodal resin based on type 1 ceramic hydroxyapatite allows for the effective removal of low-molecular-weight impurities and aggregated forms of the antibody. The antibodies obtained using the developed technology are characterized by a high degree of purity and the absence of various impurities (residual protein of the producer strain, residual protein A, and residual DNA of the producer strain), as well as offering a hydrodynamic molecular radius corresponding to the theoretical value of monomeric forms of antibodies.

Objectives. The work set out to investigate the influence of the compounding and technological parameters of polymer biocomposite materials based on polylactide (PLA) filled with the A-Len^® thermoplastic compound (Alen) on their structural, thermophysical, and mechanical properties, as well as to determine the mechanism of their destruction under the impact of ultraviolet radiation.

Methods. Films of PLA and Alen, as well as polymer composites based on them (PLA/Alen), were obtained using a flat die extruder (MashPlast, Russia). The structural and morphological properties of the films were determined with a JCM-6000 PLUS scanning electron microscope (JEOL, Akishima, Tokyo, Japan); their thermal properties were obtained using a DSC 204 F1 calorimeter (NETZSCH, Germany). The chemical composition and degradation mechanism were analyzed by infrared spectroscopy with an FSM-1201 spectrometer (Russia) fitted with an attenuated total internal reflection attachment. The mechanical properties were examined using a Z010 ZwickRoell tensile testing machine (Zwick Roell Group, Germany). The effect of ultraviolet radiation was assessed using an ultraviolet chamber.

Results. It was shown that the presence of Alen in mixtures with PLA affects the formation of a heterogeneous structure due to the presence of polyethylene in the Alen composition. This mediated a reduction in Young’s modulus by 34% (to 1050 MPa) in comparison with the initial value for PLA (1600 MPa). In the polymer composites, the PLA phase recrystallizes to yield a denser-ordered supramolecular structure, while in the polyethylene phase, the segmental mobility of macromolecules decreases and crystallization process is hindered by their different polarities to form an interface between the components under study.

Conclusions. The photodegradation mechanism in PLA/Alen polymer composites is shown to be primarily due to the presence of a prooxidant additive in Alen, which initiates the oxidation process to degrade and subsequently fragment the low-molecular fraction of polyethylene. In addition, the PLA matrix photodegrades through the Norrish Type II mechanism, which describes the oxidation of polymer chains by a radical mechanism to produce C=C bonds. The developed polymer composites are promising for the fabrication of certain polymer products due to their optimal performance characteristics and accelerated photochemical degradation kinetics.

Objectives. The effects of positive and negative temperature coefficients (PTC and NTC, respectively) in carbon black-filled conductive polymer composites based on high-density polyethylene grade 277-73 and polypropylene grade 01050 were investigated. Carbon black electrically conducting grade OMCARB C-140 (UM-76) was used as the filler.

Methods. To study the electrical characteristics of the compositions, plates were pressed with brass contact electrodes at the plate ends to simulate polymer heaters. The electrical resistance of the samples was evaluated using an ohmmeter DT9208A (RESANTA, Latvia). Tests at elevated temperatures were carried out in an SNOL 3.5 heat chamber (NPF TherMIX, Russia) with a heating rate of ~3℃/min. The crystallinity of the samples during heating was assessed by differential scanning calorimetry on a DSC 204F1 Phoenix device (NETZSCH, Germany) with a heating rate of 3℃/min.

Results. The complex PTC and NTC mechanisms in mixed polymer compositions are not solely related to thermal expansion and melting of the polymer. While changes in the electrical resistance of carbon-filled polymer composites are associated with the presence of crystalline regions with defects, the destruction of the conductive channels occurs at the earliest stages of polymer melting due to the formation of expanding amorphous “microdroplets” of the hot melt. For a carbon-filled, electrically conductive mixture of polyethylene and polypropylene, the magnitude and nature of the change in the peak temperature of the PTC depends on the melting onset temperature of the lowest-melting phase of polyethylene. At the same time, the heterogeneity of the mixtures of crystallizing polymers with technical carbon increases the thermal stability of the material by expanding the PTC zone into the melting region of the higher-melting phase of polypropylene. When comparing electrically conductive compositions of polymers with different melting points and carbon black, the low-melting polymer determines the temperature of self-regulation and the nature of PTC, while the high-melting polymer shifts the jump in electrical conductivity to the region of elevated temperatures.

Conclusions. The activation energies of carbon-filled mixtures of polyethylene and polypropylene, which are weakly dependent on the mixing method, are approximately 44 ± 3 kJ/mol. The obtained values are consistent with the activation energy values for the viscous melt flow process. The method of mixing the components in mixtures of carbon-filled compositions based on crystallizing polymers was found to have little effect on PTC. The use of carbon-filled polymer compositions with a mixed matrix of polyethylene and polypropylene allows for the regulation of the intensity of PTC and NTC.

Objectives. The work sets out to model the ozone corrosion of vulcanizates as a percolation phase transition, similar in the scheme of development of continual percolation on a plane, during which the growing regions of the new phase form a single “spanning” cluster. In this case, the continuity of the sample is broken, being divided into two parts. In the presented model, the ozone corrosion process is divided into two stages. At the first stage, ozone corrosion of the material occurs mainly along the perimeters of already ozonized surface areas, which leads to their growth and subsequent merging. Upon contact of adjacent surface areas consisting of ozonolysis products loaded with two-dimensional tension, corrosion cracks begin to appear on the surface. At the second stage of the corrosion process, corrosion cracks that grow deeply into the material due to its stress state lead to the penetration of ozone into the internal regions of the sample. The article presents the results of computer-simulation and real experiments carried out on ozone corrosion of technical vulcanizates in a plane stressed state.

Methods. Computer simulation of the time dependence of the total contact length of the areas of ozone corrosion products and the initial vulcanizate was carried out using a C++ program developed by the authors. Real experiments were carried out on a TOM-1000 setup. Samples for research by the TOM (technical ozone resistance of materials^[1]) method comprise thin disks, which are clamped along the contour and subjected to one-sided two-dimensional tension by compressed air pressure. From the side of the opposite plane, the sample is exposed to the ozone flow. The installation makes it possible to create in the sample a relative deformation of up to 100% increase in the surface area.

Results. Computer simulation allowed, in combination with direct measurements of the time dependence of ozone absorption, the dynamics of the destruction of vulcanizates in an ozone environment to be investigated. A numerical parameter of the ozone resistance of vulcanizates—the coefficient of ozone resistance—is proposed. This coefficient is almost linearly related to the time before the onset of cracking, but it is more accurate because it does not require visual observation of the ozonolysis process.

Conclusions. The results of computer simulation are in good agreement with the results of real experiments.