E. A. Skiba

Enzymatic hydrolysis of cellulose from oat husks at different substrate concentrations

Pulps prepared from oat husks via a method combining prehydrolysis, alkali delignification, and nitric acid treatment were demonstrated to possess high fermentability upon hydrolysis using multienzyme preparations, such as BrewZyme BGX and CelloLux-A. A dependence of the increment of the yield of reducing substances on the initial substrate concentration ranging from 15 to 120 g/dm3 was studied. The final yield of reducers at 72 h was shown to decline from 88 to 65% with an increase in the initial concentration of the substrate.

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).

Processing Pine Wood into Vanillin and Glucose by Sequential Catalytic Oxidation and Enzymatic Hydrolysis

Extractive-free pine wood was processed into vanillin (up to 18 wt.% of the initial lignin) and cellulose (typically 84–93% of the initial amount in the wood) by one-step catalytic oxidation followed by enzymatic hydrolysis of the resulting cellulose into glucose (reducing sugar yield up to 70% based on the post-oxidation cellulose). Correlation between the cellulose conversion in hydrolysis and the lignin content in the post-oxidation lignocellulosic material was established, which follows the general trend for the products of various delignification methods. The obtained results demonstrate the practical possibility of efficient two-step processing of wood into vanillin and glucose.

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 %).

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.

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.

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.

Early morphological changes in tissues when replacing abdominal wall defects by bacterial nanocellulose in experimental trials

AbstractExperimental trials were done on five dogs to explore if an anterior abdominal wall defect could be repaired using wet (99.9%), compact BNC membranes produced by the Мedusomyces gisevii Sa-12 symbiotic culture. The abdominal wall defect was simulated by middle-midline laparotomy, and a BNC membrane was then fixed to open aponeurotic edges with blanket suture (Prolene 4-0, Ethicon). A comparative study was also done to reinforce the aponeurotic defect with both the BNC membrane and polypropylene mesh (PPM) (Ultrapro, Ethicon). The materials were harvested at 14 and 60 days postoperative to visually evaluate their location in the abdominal tissues and evaluate the presence of BNC and PPM adhesions to the intestinal loops, followed by histologic examination of the tissue response to these prosthetics. The BNC exhibited good fixation to the anterior abdominal wall to form on the 14th day a capsule of loose fibrin around the BNC. Active reparative processes were observed at the BNC site at 60 days post-surgery to generate new, stable connective-tissue elements (macrophages, giant cells, fibroblasts, fibrin) and neocapillaries. Negligible intraperitoneal adhesions were detected between the BNC and the intestinal loops as compared to the case of PPM. There were no suppurative complications throughout the postsurgical period. We noticed on the 60th day after the BNC placement that collagenous elements and new capillary vessels were actively formed in the abdominal wall tissues, generating a dense postoperative cicatrix whose intraperitoneal adhesions to the intestinal loops were insignificant compared to the PPM graft.

Study of the Conditions for the Biosynthesis of Bacterial Cellulose by the Producer Medusomyces gisevii Sa-12

The effect of culture conditions on the bacterial cellulose (BC) yield synthesized by symbiotic culture Medusomyces gisevii Sa-12 grown in synthetic nutrient medium was studied for the first time. The conditions providing the maximum yield of bacterial cellulose were evaluated: the initial glucose concentration in the culture medium was 20–25 g/L, the temperature was 24–27°C, the ratio of the nutrient medium to the air volume was 1: 10, and the content of the black tea extracts comprised 1.6–4.8 g/L. A sample of chemically pure BC with the following characteristics was obtained under the selected culture conditions: moisture— 99.0%, degree of polymerization—4800, average width of microfibrillar ribbons—30.6 nm, degree of crystallinity— 86%, and the content of triclinic modification Iα—98%.