G. V. Sakovich

Enzymatic hydrolysis of the products of hydro-thermobaric processing of Miscanthus and oat hulls

The purpose of this work was to study the enzymatic hydrolysis of the fibrous products obtained by the hydro-thermobaric processing (with an explosion) of two types of raw materials, Miscanthus and oat hulls, in a high-pressure reactor. Multi-enzyme composition of the enzyme preparations, such as BrewZyme BGX, CelloLux-A, and Rapidase CR was used as a catalyst. It was found that the fibrous products from oat hulls exhibit the higher reactivity to fermentation as compared to Miscanthus; hydrolysis of the oat hulls processing product in a high-pressure reactor leads to the maximum yield of reducing substances, 68% (relative to the substrate weight) or 95% (relative to the weight of hydrolyzed components) with the predominance of glucose hydrolyzate. In the case of the Miscanthus processing product obtained under the same conditions, the yield of reducing substances was 44% (relative to the substrate weight) or 56% (relative to the weight of hydrolyzed components). The mass fraction of hemicelluloses in the processing products decreased to 0.4% with increasing pressure in hydro-thermobaric processing of Miscanthus; the reactivity of the products to fermentation decreased, the yield of reducing substances was 37% (relative to the substrate weight) or 55% (relative to the weight of hydrolyzed components).

Enzymatic hydrolysis of lignocellulosic materials in aqueous media and the subsequent microbiological synthesis of bioethanol

The enzymatic hydrolysis of lignocellulosic materials (LCMs) from miscanthus and oat husks (OH) in an aqueous medium and the subsequent production of ethanol are studied. LCMs are obtained at a pilot plant of the Institute of Problems of Chemical and Energy Technologies by means of one-stage nitric acid treatment. Enzymatic hydrolysis is conducted in an aqueous medium with a high initial concentration of phosphates (90 g/L) using freely available CelloLux-A and BrewZyme BGX industrial enzymatic preparations. The yields of reducing compounds are found to be 65.4 and 73.3% for miscanthus and oat husk LCM, respectively. The composition of monosaccharides (products of enzymatic LCM destruction) is studied for the first time. It is shown that glucose comprises the largest share of monosaccharides. Ethanol is produced from LCM for the first time. Ethanol yields per metric ton of raw material are 19.4 and 16.2 daL/t for miscanthus biomass and OH, respectively. Ethanol samples are characterized by low methanol contents (0.002 to 0.005 vol %).

Facile method for the synthesis of oseltamivir phosphate

A ten-step scheme for the preparation of an antiviral agent, ethyl (3R,4R,5S)-4-acetylamino-5-amino-3-(pent-3-yloxy)cyclohex-1-enecarboxylate phosphate, from (-)-shikimic acid was studied. The main parameters of the synthesis were determined and the optimal conditions for the preparation of the intermediate compounds were selected. The total yield of oseltamivir phosphate calculated based on (-)-shikimic acid was 27%.

Synthesis, properties, and application of 4-nitrosemicarbazones

The studies of the condensation of 4-nitrosemicarbazide (4-NSC) with various aldehydes and ketones resulted in the development of an approach to the synthesis of N-nitrosemicarbazones, promising high-energy and biologically active compounds. Subsequent treatment with amines and alkalis led to the synthesis of water-soluble salts of nitrosemicarbazones, as well as the corresponding semicarbazones. The reaction of N,N′-diisopropyl- or N,N′-di-tert-butyl-1,2-ethanediimine with 4-nitrosemicarbazide led to the synthesis of glyoxal bis(nitrosemicarbazone) derivatives. A computer-aided screening using the PASS software showed a probability of high biological activity for the compounds obtained, whereas antiarrhythmic properties of camphor nitrosemicarbazone potassium salt were confirmed in experiments in rats.

Kinetics of the enzymatic hydrolysis of lignocellulosic materials at different concentrations of the substrate

The kinetics of the enzymatic hydrolysis of two substrates—lignocellulosic materials from Miscanthus and oat hulls—in an acetate buffer is studied at different concentrations of the substrates. The substrates are obtained via single-step treatment with a dilute solution of nitric acid. The content of a nonhydrolyzable component—acid-insoluble lignin—for Miscanthus and oat hulls was 11 and 14%, respectively. A multi-enzyme composition of commercially available enzyme preparations CelloLux-A and BrewZyme BGX was used as a catalyst. It is shown that treatment with the nitric acid solution produces reactive substrates for the enzymatic hydrolysis. The innovative science of the results is confirmed by Russian patent 2533921. Kinetics of the enzymatic hydrolysis of these substrates in an acetate buffer can be described by a mathematical model based on a modified Michaelis–Menten equation. The main kinetic constants for both substrates are determined from the experimental data. The equilibrium concentrations of reducing substances (RSes) for the substrates are calculated from the initial substrate concentrations. It is found that within the studied range of substrate concentrations (33.3–120.0 g/L), the initial rate of enzymatic hydrolysis for the lignocellulosic material from oat hulls is higher than that for the lignocellulosic material from Miscanthus by 1 g/(L h). It is shown that the yield of RS depends of the initial concentration of the substrates: as the concentration rises from 33.3 to 120 g/L, the yield of RS falls 1.5–2.0 times, due to substrate inhibition. At low initial concentrations, the yields of RS are similar for the substrates from Miscanthus and oat hulls. When the initial concentration of the substrate reaches 120 g/L, the yield of reducing substances for the lignocellulosic material from Miscanthus is approximately 20% higher than that for the lignocellulosic material from oat hulls. The established dependences and the proposed mathematical model allow us to optimize the initial concentration of the substrate for efficient enzymatic hydrolysis.

Furfural nitrosemicarbazone salts

Furfural 4-nitrosemicarbazone potassium and sodium salts were synthesized. The structures of these compounds were studied by IR and NMR spectroscopy and X-ray diffraction. The computer screening with the PASS program revealed higher biological activity of the salts compared to the starting furfural 4-nitrosemicarbazone.

Technological fundamentals of bacterial nanocellulose production from zero prime-cost feedstock

The concept of manufacturing valuable bacterial nanocellulose (BNC) from plant raw materials having a zero prime cost is substantiated. The process flowsheet involves the chemical transformation of the feedstock to obtain a pulp; enzymatic hydrolysis of the pulp to furnish a solution of reducing sugars, chiefly glucose; preparation of a nutrient broth based on the enzymatic hydrolysate; biosynthesis of nanocellulose microfibrils by the symbiotic Medusomyces gisevii Sa-12 culture; and purification of BNC. BNC has for the first time been synthesized from oat hulls and has a high degree of crystallinity of 88 ± 5% and is composed of 99% Iα-allomorph.

Preparing bioethanol from oat hulls pretreated with a dilute nitric acid: Scaling of the production process on a pilot plant

The full cycle of bioethanol production from pretreated oat hulls is scaled for a pilot plant. The one-stage pretreatment of oat hulls with a dilute nitric acid at atmospheric pressure is scaled for a 250-L reactor. The total amount of hydrolysable polysaccharides in the resulting substrate is 87.2%. Using the commercially available enzyme preparations CelloLux-A and BrewZyme BGX and the industrial strain BKPM Y-1693 of Saccharomyces cerevisiae yeast, the process of enzymatic hydrolysis and alcoholic fermentation is successfully scaled for a 63-L reactor. The scaling factor is 1: 400. Bioethanol is obtained with a high yield of 17.9 daL/t. After rectification, the test sample of bioethanol meets the standards for high-purity alcohol from food raw materials according to the mass concentration of aldehydes, esters, and by the content of methanol.

The characteristics of the hydrotropic Miscanthus pulp

The characteristics of the Miscanthus pulp obtained by hydrotropic processing under different conditions were studied. The pulping conditions were optimized to achieve the 42.3% yield of the pulp (lignin content 6.1%, pentosan content 6.4%, and ash content 3.0%). The hydrotrope selectively solubilizes lignin; the delignification is closely associated with the primary dissolution of carbohydrates.

Enzymatic Hydrolysis of Celluloses Obtained via the Hydrothermal Processing of Miscanthus and Oat Hulls

The enzymatic hydrolysis of celluloses obtained via the refinement of fibrous products after the hydro-thermobaric processing (with an explosion) of two types of feedstocks (Miscanthus and oat hulls) in a high-pressure reactor is studied. A multi-enzyme composition of such enzyme preparations as CelloLux-A, BrewZyme BGX, and Rapidase CR, is used as a catalyst. The celluloses obtained by refining fibrous products from the mentioned feedstocks at a pressure of 1.5 MPa are found to have close reactivities: the yield of reducing substances (RS) was 81% (relative to the substrate weight) and 87–91% (relative to the weight of hydrolyzable compounds). When the pressure of the hydro-thermobaric treatment processing of the feedstocks (Miscanthus) is raised from 1.5 to 2.5 MPa, the fermentability of celluloses diminishes: the RS yield was 53–57% (relative to the substrate weight) or 56–60% (relative to the weight of hydrolyzable compounds). The universality of the hydro-thermobaric processing of different non-wood feedstocks for the subsequent successive fermentolysis of substrates into RS solutions that predominantly contain cellulose is shown. The obtained glucose hydrolyzates are high-quality feedstocks for the biosynthesis not only of fuel alcohols, but also a wide spectrum of such microbiosynthesis products as aminoacids, organic acids, bacterial cellulose jelly films, and protein-vitamin concentrates.