Range Of Substrate Concentrations Research Articles

Sex-Linked Changes in Biotransformation of Phenol in Brook Trout (Salvelinus fontinalis) over an Annual Reproductive Cycle

The microsomal metabolism of phenol (11 °C) over an annual reproductive cycle from June to December was studied using fall spawning adult brook trout (Salvelinus fontinalis). Hepatic microsomes were isolated from three male and three female fish each month. Incubations were optimized for time, cofactor concentration, pH, and microsomal protein concentration. The formation of phase I ring-hydroxylation metabolites, i.e., hydroquinone (HQ) and catechol (CAT), was quantified by HPLC with dual-channel electrochemical detection. Sample preparation and chromatographic conditions were optimized to achieve the separation and sensitivity required for the analysis of these labile products. Biotransformation of phenol over a range of substrate concentrations (1 to 150 mM) was quantified for the calculation of Michaelis–Menten constants (Km and Vmax) for each month. Results indicate a nearly equal production of HQ and CAT among males and females in late June. At the peak of maturity in October, there was an approximate ten-fold greater production of ring-hydroxylation metabolites noted in females in comparison with males on a total liver basis. In vitro phase II biotransformation of phenol glucuronidation was assessed by determining the Michaelis–Menten constants (Km, Vmax) using brook trout hepatic microsomes over a range of substrate concentrations (1 to 60 mM). Initially, there were no significant differences in the glucuronide rate of formation (pmol/min/mg protein) or total capacity (nmol/min/liver) between females and males. At the peak of maturation, the maximum rate of glucuronide formation was 4-fold less in females; however, the total capacity was 2-fold less in females due to the increased liver size in the females. The alterations in biotransformation coincided with increases in the hepatic and gonadal somatic indices and with changes in plasma hormone concentrations. These experiments provide insight into the metabolic deactivation of xenobiotics and to provide data for the prediction of altered hepatic biotransformation rates and pathways during the reproductive cycle.

Substrate-induced phase transition within liquid condensates reverses the catalytic activity of nanoparticles.

Liquid-liquid phase separation is reported to enhance the catalytic reaction rates severalfold. Herein, we explored the interactions between a catalyst and a range of substrate concentrations to understand the impact on the droplet phase and catalytic reaction kinetics. We observed that the substrate above a critical concentration induces phase transitions within liquid condensates and restricts the free movement of both the substrate and products, resulting in an overall reduction of the reaction rate, an observation not reported earlier.

A Comparative Study of Phase I and II Hepatic Microsomal Biotransformation of Phenol in Three Species of Salmonidae: Hydroquinone, Catechol, and Phenylglucuronide Formation

The in vitro biotransformation of phenol at 11 °C was studied using pre-spawn adult rainbow (Oncorhynchus mykiss) (RBT), brook (Salvelinus fontinalis) (BKT), and lake trout (Salvelinus namaycush) (LKT) hepatic microsomal preparations. The incubations were optimized for time, cofactor concentration, pH, and microsomal protein concentration. Formation of Phase I ring-hydroxylation and Phase II glucuronidation metabolites was quantified using HPLC with dual-channel electrochemical and UV detection. The biotransformation of phenol over a range of substrate concentrations (1 to 180 mM) was quantified, and the Michaelis–Menten kinetics constants, Km and Vmax, for the formation of hydroquinone (HQ), catechol (CAT), and phenylglucuronide (PG) were calculated. Species differences were noted in the Km values for Phase I enzyme production of HQ and CAT, with the following rank order of apparent enzyme affinity for substrate: RBT > BKT = LKT. However, no apparent differences in the Km for Phase II metabolism of phenol to PG were detected. Conversely, while there were no apparent differences in Vmax between species for HQ or CAT formation, the apparent maximum capacity for PG formation was significantly less in LKT than that observed for RBT and BKT. These experiments provide a means to quantify metabolic activation and deactivation of xenobiotics in fish, to compare activation and deactivation reactions across species, and to act as a guide for future predictions of new chemical biotransformation pathways and rates in fish. These experiments provided the necessary rate and capacity (Km and Vmax) inputs that are required to parameterize a fish physiologically based toxicokinetic (PB-TK) model for a reactive chemical that is readily biotransformed, such as phenol. In the future, an extensive database of these rate and capacity parameters on important fish species for selected chemical structures will be needed to allow the effective use of predictive models for reactive, biotransformation chemicals in aquatic toxicology and environmental risk assessment.

Synergistic effects of peroxydisulfate on UV/O3 process for tetracycline degradation: Mechanism and pathways

Tetracycline (TC) as a typical emerging pollutant is becoming a serious threat to the environment and human health. A combined advanced oxidation technology of UV/Ozone (O3)/peroxydisulfate (PDS) process was developed to explore an efficient and economic treatment process of TC in wastewater. Furthermore, the reactive sites and transformation pathways of TC were explored and the toxicity of the intermediates was quantified with a quantitative structure-activity relationship (QSAR) assessment. The degradation performance of TC was substantially enhanced in UV/O3/PDS process with a kobs of 0.0949 min−1, which was 2.3 times higher than UV/O3 and 3.2 times than sole UV. The results demonstrated that there was a superior synergistic effect of PDS on UV/O3 processes for the degradation of TC. Electron paramagnetic resonance (EPR) analysis and quenching experiments show that •OH, SO4•−, O2•− and 1O2 all contributed to TC degradation in the UV/O3/PDS process and exhibited a synergistic effect, which inhibited the generation of harmful products. In addition, the UV/O3/PDS system can effectively degrade TC in a wide range of substrate concentrations and pH, and also showed excellent adaptability to various concentrations of anions (Cl− and HCO3−). This study proves the feasibility of UV/O3/PDS process for treating TC contaminated wastewater with complicated water matrix.

Unexpected Single-Ligand Occupancy and Negative Cooperativity in the SARS-CoV-2 Main Protease.

Many homodimeric enzymes tune their functions by exploiting either negative or positive cooperativity between subunits. In the SARS-CoV-2 Main protease (Mpro) homodimer, the latter has been suggested by symmetry in most of the 500 reported protease/ligand complex structures solved by macromolecular crystallography (MX). Here we apply the latter to both covalent and noncovalent ligands in complex with Mpro. Strikingly, our experiments show that the occupation of both active sites of the dimer originates from an excess of ligands. Indeed, cocrystals obtained using a 1:1 ligand/protomer stoichiometry lead to single occupation only. The empty binding site exhibits a catalytically inactive geometry in solution, as suggested by molecular dynamics simulations. Thus, Mpro operates through negative cooperativity with the asymmetric activity of the catalytic sites. This allows it to function with a wide range of substrate concentrations, making it resistant to saturation and potentially difficult to shut down, all properties advantageous for the virus' adaptability and resistance.

CHARACTERIZATION OF A NEWLY ISOLATED AZO-DYE DEGRADING KLEBSIELLA SP. STRAIN RGUDBI01

Azo-dyes such as crystal violet are commonly used ingredient in all types of dying industries which more often eventually reach water and soil due to washing and disposal practices. They are non-biodegradable inside higher organisms and are less biodegradable due to their xenobiotic character. However, some of the microbes exhibit their extensive potential to degrade such recalcitrants. This study reports the isolation and characterization of a newly isolated Klebsiella sp. strain RGUDBI01 from petroleum-contaminated soil samples. The species-level identification was done by 16S rDNA gene sequencing (ON945611.1). The isolate exhibited 88% azo-dye degradation just after 3 days of incubation under optimized conditions. The treated samples exhibited a significant increase in the growth of Cicer arietinum seeds compared to the control group. This result suggests that the dye-contaminated samples, after treatment, displayed non-cytotoxic behavior. The strain also showed its potential to tolerate and withstand a wide range of pH, salinity, and substrate concentration which supports its futuristic environmental application. In addition to the above, the strain could also produce biosurfactants with ʋC=C, ʋC=C-H, and ʋC-C functional groups which were evaluated based on FTIR spectral analysis.

The pH-dependent lactose metabolism of Lactobacillus delbrueckii subsp. bulgaricus: An integrative view through a mechanistic computational model.

The fermentation process of milk to yoghurt using Lactobacillus delbrueckii subsp. bulgaricus in co-culture with Streptococcus thermophilus is hallmarked by the breakdown of lactose to organic acids such as lactate. This leads to a substantial decrease in pH - both in the medium, as well as cytosolic. The latter impairs metabolic activities due to the pH-dependence of enzymes, which compromises microbial growth. To quantitatively elucidate the impact of the acidification on metabolism of L. bulgaricus in an integrated way, we have developed a proton-dependent computational model of lactose metabolism and casein degradation based on experimental data. The model accounts for the influence of pH on enzyme activities as well as cellular growth and proliferation of the bacterial population. We used a machine learning approach to quantify the cell volume throughout fermentation. Simulation results show a decrease in metabolic flux with acidification of the cytosol. Additionally, the validated model predicts a similar metabolic behaviour within a wide range of non-limiting substrate concentrations. This computational model provides a deeper understanding of the intricate relationships between metabolic activity and acidification and paves the way for further optimization of yoghurt production under industrial settings.

3βHSD activity saturates at physiological substrate concentrations in intact cells.

Conversion of adrenally produced dehydroepiandrosterone (DHEA) to the potent androgen dihydrotestosterone (DHT) is an important mechanism by which prostate cancer reaches castration resistance. At the start of this pathway is a branch point at which DHEA can be converted to Δ4 -androstenedione by the enzyme 3β-hydroxysteroid dehydrogenase (3βHSD) or to Δ5 -androstenediol by 17βHSD. To better understand this process, we studied the kinetics of these reactions in cells. Prostate cancer cells (LNCaP cell line) were incubated with steroids (DHEA and Δ5 -androstenediol) over a range of concentrations and the steroid metabolism reaction products were measured by mass spectrometry or by high-performance liquid chromatography to determine reaction kinetics. To confirm the generalizability of results, experiments were also performed in JEG-3 placental choriocarcinoma cells. The two reactions displayed very different saturation profiles, with only the 3βHSD-catalyzed reaction beginning to saturate within a physiological substrate concentration range. Strikingly, incubating LNCaP cells with low (in the ~10 nM range) concentrations of DHEA resulted in a large majority of the DHEA undergoing 3βHSD-catalyzed conversion to Δ4 -androstenedione, whereas high concentrations of DHEA (in the 100s of nM range) resulted in most of the DHEA undergoing 17βHSD-catalyzed conversion to Δ5 -androstenediol. Contrary to expectations from previous studies that used purified enzyme, cellular metabolism of DHEA by 3βHSD begins to saturate in the physiological concentration range, suggesting that fluctuations in DHEA concentrations could be buffered at the downstream active androgen level.

Fluorimetric microplate assay for the determination of extracellular alkaline phosphatase kinetics and inhibition kinetics in activated sludge

The microbial enzyme alkaline phosphatase contributes to the removal of organic phosphorus compounds from wastewaters. To cope with regulatory threshold values for permitted maximum phosphor concentrations in treated wastewaters, a high activity of this enzyme in the biological treatment stage, e.g., the activated sludge process, is required. To investigate the reaction dynamics of this enzyme, to analyze substrate selectivities, and to identify potential inhibitors, the determination of enzyme kinetics is necessary. A method based on the application of the synthetic fluorogenic substrate 4-methylumbelliferyl phosphate is proven for soils, but not for activated sludges. Here, we adapt this procedure to the latter. The adapted method offers the additional benefit to determine inhibition kinetics. In contrast to conventional photometric assays, no particle removal, e.g., of sludge pellets, is required enabling the analysis of the whole sludge suspension as well as of specific sludge fractions. The high sensitivity of fluorescence detection allows the selection of a wide substrate concentration range for sound modeling of kinetic functions.•Fluorescence array technique for fast and sensitive analysis of high sample numbers•No need for particle separation – analysis of the whole (diluted) sludge suspension•Simultaneous determination of standard and inhibition kinetics

Tunable Enzyme-Assisted Mineralization of Apatitic Calcium Phosphate by Homogeneous Catalysis

While it has long been mimicked by simple precipitation reactions under biologically relevant conditions, calcium phosphate biomineralization is a complex process, which is highly regulated by physicochemical factors and involves a variety of proteins and other biomolecules. Alkaline phosphatase (ALP), in particular, is a conductor of sorts, directly regulating the amount of orthophosphate ions available for mineralization. Herein, we explore enzyme-assisted mineralization in the homogeneous phase as a method for biomimetic mineralization and focus on how relevant ionic substitution types affect the obtained minerals. For this purpose, mineralization is performed over a range of enzyme substrate concentrations and fluoride concentrations at physiologically relevant conditions (pH 7.4, T = 37 °C). Refinement of X-ray diffraction data is used to study the crystallographic unit cell parameters for evidence of ionic substitution in the lattice, and infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) are used for complementary information regarding the chemical composition of the minerals. The results show the formation of substituted hydroxyapatite (HAP) after 48 h mineralization in all conditions. Interestingly, an expansion of the crystalline unit cell with an increasing concentration of the enzyme substrate is observed, with only slight changes in the particle morphology. On the contrary, by increasing the amount of fluoride, while keeping the enzyme substrate concentration unchanged, a contraction of the crystalline unit cell and the formation of elongated, well-crystallized rods are observed. Complementary IR and XPS data indicate that these trends are explained by the incorporation of substituted ions, namely CO32- and F-, in the HAP lattice at different positions.

Highly sensitive cholesterol biosensor based on electron mediator thionine and cubic-shaped Cu2O nanomaterials

The preparation of an electrochemical biosensor applicable for the highly sensitive detection of cholesterol content in biological samples in clinical practice is studied in this paper. Commonly used in biosensors, nano-cuprous oxide (Cu2O) contains active electron-hole pairs and a large specific surface area, while thionine (TH) improves the efficiency of electron transfer between the enzyme and the electrode. In this study, a cholesterol biosensor, cholesterol oxidase (ChOx)/thionine/nano-cuprous oxide/ glassy carbon electrode (GCE) (ChOx/TH/Cu2O/GCE), is prepared using cubic-shaped Cu2O as the nanomaterial, TH as an electron mediator, and chitosan (CS) as a cross-linking agent to immobilize cholesterol oxidase. The results show that Cu2O nanoparticles (NPs) are successfully synthesized, and the cholesterol biosensor prepared from synthesized Cu2O NPs exhibits excellent electrochemical characteristics, good linearity (R2 = 0.997) over a substrate concentration range of 10 to 1000 µM, a sensitivity of 70.22 µA µM−1 cm−2, and a low detection limit of 0.0018 µM for the substrate. The ChOx, which immobilizes on the composite electrode, shows a strong affinity for cholesterol due to its low Michaelis–Menten constant (Km) value (25.359 µM). Moreover, with strong anti-interference, good reproducibility, and stability, the cholesterol biosensor can achieve a recovery rate of 99.71 % to 107.75 % according to a recovery test of actual spiked samples. Thus, the prepared nanomaterial-based cholesterol biosensor can be applied to the highly sensitive detection of cholesterol in actual biological samples.

Rate constants are determinable outside the original Michaelis–Menten mathematical formalism wherein the substrate concentration range is approx. 1.6 to 4.8 times enzyme concentration: A pre-steady-state scenario and beyond

Rate constants are determinable outside the original Michaelis–Menten mathematical formalism wherein the substrate concentration range is approx. 1.6 to 4.8 times enzyme concentration: A pre-steady-state scenario and beyond

Rate constants are determinable outside the original Michaelis–Menten mathematical formalism wherein the substrate concentration range is  1.6  4.8 times enzyme concentration: A pre-steady-state scenario and beyond

For some time now, there has been growing interest in pre-steady-state (PSS) kinetic parameters for whatever reasons, the measurement of which needs high-tech equipment capable of transient time-scale duration of assay. The proposition, however, is that all kinetic parameters, PSS and beyond, can be determined with appropriate PSS derivable equations and the usual Michaelis-Menten (MM) and Briggs-Haldane (BH) equations, respectively. The objectives of the research were: 1) To derive equations, for the determination of reverse rate constant when the substrate concentration, [S] « MM constant, KM, 2) determine by calculation, the reverse rate constant, forward rate constant, and consequently, show that it is possible to determine rate constant often seen to be masked within original MM cum BH mathematical formalism, and 3) validate corollaries from the derivation that justify procedural issue. Theoretical, experimental (Bernfeld method), and computational methods were explored. Pre-steady-state equations for the determination of kinetic parameters, the reverse rate constant, k-1, for the process ES ® E + S, the 2nd order rate constant, k1, and the rate, v1, for the formation of enzyme-substrate complex, ES, were derived. The derived originating equations with associated corollaries were validated and have been seen to be capable of reproducing experimental variables and kinetic parameters; rate constants that seemed masked in MM formalism were unmasked. Steady-state (SS) cum zero order kinetic parameters were » their PSS values. “Negative” catalytic efficiency (k-1/KM) was » “positive” catalytic efficiency, (kcat/KM), with lower [ET]. In conclusion, the equations for PSS kinetic parameters were derivable. Previously masked kinetic parameters in the MM/BB mathematical formalism can now be calculated using MM data; thus, all kinetic parameters can be determined regardless of the reaction pathway's state, PSS, and SS. PSS kinetic parameters were « SS/zero order values.

Synergistic and efficient degradation of acid red 73 by UV/O3/PDS: Kinetic studies, free radical contributions and degradation pathways

Acid red 73 (AR73) is a representative dye pollutant that poses a threat to the environment and human health. Effectively removing this type of pollutant by conventional processes is difficult. However, this study found that compared with UV/PDS, UV/O3, and PDS/O3, UV/O3/PDS composite system had the highest degradation effect on AR73. The degradation efficiency in the composite system reached 97.61% within 30 min, and the synergistic coefficients in the composite system were all greater than 1. In the UV/O3/PDS system, ·OH was the main free radical that mainly degrades AR73. The increase of PDS dosage promoted the degradation of AR73, but the increase of O3 dosage was difficult to greatly improve the degradation of AR73 effect. The kinetic model of the apparent reaction rate was determined. The UV/O3/PDS system can efficiently degrade AR73 in a wide range of substrate concentrations and pH levels, and at the same time showed good adaptability to various concentrations of anions (Cl−, CO32−, SO32−, and C2O42−). Under raw water quality, the degradation effect of AR73 was still as high as approximately 90%. The theoretical attack site was obtained by DFT calculation, and the possible degradation pathway of AR73 was proposed based on the GC-MS spectrum and UV–Vis absorption spectrum. The attack of –NN- by ·OH, SO4−, and O3 was proposed to be the main possible degradation pathway for AR73. Therefore, this study further improves the understanding of the UV/O3/PDS system and shows the potential applicability of this system in the treatment of dye wastewater.

Selectivity and kinetic modeling of penicillin G acylase variants for the synthesis of cephalexin under a broad range of substrate concentrations.

The kinetics of cephalexin synthesis and hydrolysis of the activated acyl-donor precursor phenylglycine methyl ester(PGME) were characterized under a broad range of substrate concentrations. A previously developed model by Youshko-Svedas involving the formation of the acyl-enzyme complex followed by binding of the nucleophilic β-lactam donor does not fully estimate the maximum reaction yields for cephalexin synthesis at different concentrations using initial-rate data. 7-aminodesacetoxycephalosporanic acid(7-ADCA) was discovered to be a potent inhibitor of cephalexin hydrolysis, which may account for the deviation from model predictions. Three kinetic models were compared for cephalexin synthesis, with the model incorporating competitive inhibition due to 7-ADCA yielding the best fit. Additionally, the βF24A variant and Assemblase® did not exhibit significantly different kinetics for the synthesis of cephalexin compared to the wild-type, for the concentration range evaluated and for both initial-rate experiments and time-course synthesis experiments. Lastly, a continuous stirred-tank reactor for cephalexin synthesis was simulated using the model incorporating competitive inhibition by 7-ADCA, with clear tradeoffs observed between productivity, fractional yield, and PGME conversion.

CHICKEN FEATHER DEGRADATION BY KERATINOLYTIC ASPERGILLUS SPECIES ISOLATED FROM FEATHER WASTE DUMPING SOIL

Slaughterhouses and poultry processing units worldwide dispose of huge amount of chicken feathers that accumulate as solid waste in the environment and cause serious consequences. Keratinases are a group of enzymes, produced by microorganisms have the ability to degrade tough recalcitrant keratin that is abundantly present in chicken feathers. Soil sample was collected from a feather dumping site at Virudhunagar (9° 35' 13.9524'’ N Latitude and 77° 57' 5.1516'’ E Longitude), Tamil Nadu, India. Soil sample was serially diluted, inoculated on to feather meal agar plates and incubated at 37 °C for 7 days to isolate keratinolytic fungal strains. The isolated strains were screened for proteolytic activity on skim milk agar for 8 days and three better strains were identified based on morphology, mycelial growth, and structure of hyphae using lactophenol cotton blue staining and confirmed by ITS primer sequencing method as Aspergillus niger, Aspergillus terreus and Aspergillus flavus respectively. Different range of pH (7 to 11), temperature (25 to 45 °C), substrate (bovine serum albumin, feather, peptone and gelatin) and feather concentration (0.5g, 1g, 1.5g and 2g) were tested to find out the optimum conditions for the growth and keratin degradation of the chosen fungal strains. The temperature and feather concentration for the optimum growth of A. niger, A. terreus and A. flavus were 25 °C and 1.5g, 45 °C and 1g and 30 °C and 1.5g respectively. All three Aspergillus species exerted better growth at pH 9 and with bovine serum albumin as the substrate.

Use of selective substrates and inhibitors to rapidly characterise batches of cryopreserved primary human hepatocytes for assessment of active uptake liability in drug discovery and development

The use of hepatocytes to predict human hepatic metabolic clearance is the gold standard approach. However whilst enzymes are well characterised, knowledge gaps remain for transporters. Furthermore, methods to study specific transporter involvement are often complicated by overlapping substrate specificity. Selective substrates and inhibitors would aid investigations into clinically relevant pharmacokinetic effects. However, to date no consensus has been reached. This work defines selective hepatic uptake transporter substrates and inhibitors for the six main human hepatocyte transporters (OATP1B1, OATP1B3, OATP2B1, NTCP, OAT2 & OCT1), and demonstrates their use to rapidly characterise batches of human hepatocytes for uptake transporter activity. Hepatic uptake was determined across a range of substrate concentrations, allowing the definition of kinetic parameters and hence active and passive components. Systematic investigations identified a specific substrate and inhibitor for each transporter, with no overlap between the specificity of substrate and inhibitor for any given transporter. Early characterisation of compound interactions with uptake transporters will aid in early risk assessment and chemistry design. Hence, this work further highlights the feasibility of a refined methodology for rapid compound characterisation for the application of static and dynamic models, for early clinical risk assessment and guidance for the clinical development plan.

Kinetic modeling of succinate production from glucose and xylose by metabolically engineered Escherichia coli KJ12201

This study proposed a kinetic model for succinate production from xylose and glucose by Escherichia coli KJ12201 based on the Monod equation in which inhibitions of xylose or glucose and succinate were simultaneously considered. Our proposed model showed the strong inhibition effect by xylose on the specific growth rate while glucose had no inhibitory effect. Additionally, maximum concentrations of succinate that completely inhibited the cell growth were 60.70 g/L for xylose and 82.71 g/L for glucose. The kinetic parameters of the proposed model were determined by minimizing the gap between experimental data and the model prediction. With estimated kinetic parameters, values solved by the proposed model aligned and suited experimental data in the range of substrate concentrations (20–80 g/L) used. The sensitivity analysis also revealed that the maximum specific growth rate (µmax) and the maximum inhibitory xylose concentration (C*xylose) provided extreme influences on the succinate production. Our proposed model was then validated and found that it precisely predicted the cell growth, substrate utilization and succinate production by the strain. The proposed model may be employed for effectively controlling and optimizing the succinate production from other substrates containing glucose and xylose in a large-scale process by E. coli KJ12201.

Modeling and Simulation of Batch Sugarcane Alcoholic Fermentation Using the Metabolic Model

The present work sought to implement a model different from the more traditional ones for the fermentation process of ethanol production by the action of the fungus Saccharomyces cerevisiae, using a relevant metabolic network based on the glycolytic Embden–Meyerhof–Parnas route, also called “EMP”. We developed two models to represent this phenomenon. In the first model, we used the simple and unbranched EMP route, with a constant concentration of microorganisms throughout the process and glucose as the whole substrate. We called this first model “SR”, regarding the Portuguese name “sem ramificações”, which means “no branches”. We developed the second model by simply adding some branches to the SR model. We called this model “CR”, regarding the Portuguese name “com ramificações”, which means “with branches”. Both models were implemented in MATLABTM software considering a constant temperature equal to 32 °C, similar to that practiced in sugar and ethanol plants, and a wide range of substrate concentrations, ranging from 30 to 100 g/L, and all the enzymes necessary for fermentation were already expressed in the cells so all the enzymes showed a constant concentration throughout the fermentation. The addition of common branches to the EMP route resulted in a considerable improvement in the results, especially predicting ethanol production closer to what we saw experimentally. Therefore, the results obtained are promising, making adjustments consistent with experimental data, meaning that all the models proposed here are a good basis for the development of future metabolic models of discontinuous fermentative processes.

OPTIMIZATION OF THE PROCESS OF SACCHARIFICATION OF HARDWOOD CELLULOSE UNDER THE ACTION OF HYDROLASES AND OXYGENASES

A complex of enzymes has been selected for the exhaustive enzymatic conversion of semi-bleached sulfate hardwood pulp to monosaccharides, carried out in the substrate concentration range from 100 to 300 g/l. The role of cellulases, xylanase, β-glucosidase and polysaccharide monooxygenase in the intensification of the process is shown.