Final Product Concentration Research Articles

Novel Study of Reaction Kinetics and Mass Transfer in Bioreactor Modelling: Prediction of Bioethanol Fermentation Performance by Saccharomyces cerevisiae on Continuous Fixed Bed Biofilm Plug Flow Reactor

Bioethanol implementation as a renewable fuel has yielded economic, social, and environmental benefits, including reduced fossil fuel consumption, enhanced energy diversity and supply security, lower greenhouse gas emissions, and support for agricultural communities. These impacts underscore the importance of advancing innovation and optimizing processes to increase bioethanol production. Therefore, basic knowledge of chemical engineering in bioethanol fermentation is important to be learnt as a preliminary study, such as reaction kinetics and transport phenomena. This work studies the reaction kinetics and mass transfer in continuous fixed bed biofilm plug flow reactor modelling to predict anaerobic Saccharomyces cerevisiae fermentation performance, which is still not studied comprehensively. This modelling provides an overview of the influence of various independent variables, namely temperature, initial substrate concentration, cell concentration, superficial flow rate, reactor diameter, and solid particle diameter on various dependent variables, namely final product concentration, residence time, reactor length, reactor volume, product productivity, and pressure drop. The most sensitive parameters related to product productivity are temperature and cell concentration, so in its implementation, the temperature must be controlled at its optimum temperature, and the inoculum must be prepared with high cell concentration. For the next study, it is recommended to study the optimization of reactor design and operation (i.e. the pumping system, cooling system, and pH control of the reactor) and the implementation of the reactor on the plant scale. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Recycling potato waste for the production of blue pigments by Streptomyces lydicus PM7 through submerged fermentation

BackgroundDiscarded potato is the most abundant potato waste and represents a worldwide disposal problem to the potato industry. This agricultural waste contains valuable nutrients that could be used as substrate to obtain diverse high value-added microbial products, such as biopigments. The aim of this work was to evaluate the use of discarded potato as a sole substrate source for producing blue pigments by Streptomyces lydicus PM7 through submerged fermentation.ResultsInitially, the traditional culture medium ISP2 was established as suitable for inoculum preparation, as it allowed high growth rates and consumption of ~ 75% reducing sugar, leading to 1.3 g L−1 dry biomass at 72 h of incubation. The formulated discarded potato broth (DPB) medium was evaluated together with five other traditional liquid culture media (potato dextrose broth, ISP2, ISP3, ISP4, and ISP5) for producing blue pigments by S. lydicus PM7. The highest blue pigment production was obtained by using DPB medium, reaching ~ 0.97 g L−1, followed by ISP5 (~ 0.36 g L−1). In terms of evaluating the concentration of discarded potato powder, the highest concentration of blue pigments was obtained with 16 g L−1, compared to concentrations of 4, 8, and 32 g L−1. In general, a notable increase in total proteins (~ 14 g L−1 in biomass; ~ 8 g L−1 in medium) and reducing sugars (~ 5 g L−1) on the fifth day of DPB fermentation was observed, at which time the production of blue pigments began. These data proved that S. lydicus PM7 is able to degrade potato wastes during submerged fermentation and to direct metabolism towards the formation of biopigments. Chromatographic analysis revealed that the main blue pigment produced by new strain in this complex medium is actinorhodin.ConclusionsDiscarded potato favored the production of blue pigments by S. lydicus PM7 under submerged fermentation, leading to final product concentration almost three times higher than others traditional Streptomyces culture media. To the best of our knowledge, this is the first report on the production of actinorhodin by the specie S. lydicus, as well as on this pigment synthesis based on an agricultural waste as a sole nutrient source for fermentation process. The findings showed that potato waste could be a potential byproduct for replacement of commercial culture media using for this same purpose.Graphical

2-nitro-4-nonylphenol-based extractant for selective extraction of lithium from carbonate precipitation mother liquors

In this work, for the first time we proposed a mixture based on 2-nitro-4-nonylphenol as a lithium-selective binary extractant, in which the nitro group simultaneously participates in the formation of a six-membered metallocycle and increases the acidity of the phenolic group. The extraction of alkali metals (Li, Na, K) by a mixture of 2-nitro-4-nonylphenol and trioctylphosphinoxide in dodecane was studied in detail. The extraction of Li from mother liquors after Li2CO3 precipitation was considered as a practical application of the new binary extractant. It was shown that by using only liquid extraction methods, a high degree of concentration and purification of final product can be achieved. Mother liquor of Li2CO3 precipitation was concentrated by Li more than 50 times. Degree of lithium concentrate purification from Na and K was more than 5500 and 100,000 times, correspondingly.

High cell density sequential batch fermentation for enhanced propionic acid production from glucose and glycerol/glucose mixture using Acidipropionibacterium acidipropionici

BackgroundPropionic acid fermentation from renewable feedstock suffers from low volumetric productivity and final product concentration, which limits the industrial feasibility of the microbial route. High cell density fermentation techniques overcome these limitations. Here, propionic acid (PA) production from glucose and a crude glycerol/glucose mixture was evaluated using Acidipropionibacterium acidipropionici, in high cell density (HCD) batch fermentations with cell recycle. The agro-industrial by-product, heat-treated potato juice, was used as N-source.ResultsUsing 40 g/L glucose for nine consecutive batches yielded an average of 18.76 ± 1.34 g/L of PA per batch (0.59 gPA/gGlu) at a maximum rate of 1.15 gPA/L.h, and a maximum biomass of 39.89 gCDW/L. Succinic acid (SA) and acetic acid (AA) were obtained as major by-products and the mass ratio of PA:SA:AA was 100:23:25. When a crude glycerol/glucose mixture (60 g/L:30 g/L) was used for 6 consecutive batches with cell recycle, an average of 35.36 ± 2.17 g/L of PA was obtained per batch (0.51 gPA/gC-source) at a maximum rate of 0.35 g/L.h, and reaching a maximum biomass concentration of 12.66 gCDW/L. The PA:SA:AA mass ratio was 100:29:3. Further addition of 0.75 mg/L biotin as a supplement to the culture medium enhanced the cell growth reaching 21.89 gCDW/L, and PA productivity to 0.48 g/L.h, but also doubled AA concentration.ConclusionThis is the highest reported productivity from glycerol/glucose co-fermentation where majority of the culture medium components comprised industrial by-products (crude glycerol and HTPJ). HCD batch fermentations with cell recycling are promising approaches towards industrialization of the bioprocess.

Integrated Waste-to-Energy Process Optimization for Municipal Solid Waste

Within the past few decades, thousands of experiments have been performed to characterize urban waste and biomass to estimate their bioenergy potential and product identification. There is a need to develop an integrated process model based on the experimental literature, as well as simulations to obtain suitable products. In this study, municipal solid waste (MSW), including paper and plastic characterization and an integrated process model, were developed to optimize the final products in a reactor system. The process model has two modes, R&D and reactor control (RC), to obtain suitable products including bio-oil, char, and gases. A database was integrated based on thermokinetics, machine learning, and simulation models to optimize product efficiency. The experimental data include those obtained by thermogravimetric analysis and Fourier-transform infrared spectroscopy, which were linked to a pyrolysis experimental setup. Feedstock product mapping models were incorporated into the database along with the temperature, heating rates, elemental analysis, and final product concentration, which were utilized for the pyrolysis reactor setup. Product feasibility was conducted based on life cycle cost, affordability, and product efficiency. The present work will bridge the gap between experimental studies and decision-making based on obtained products under several experimental conditions around the world.

The Sustainable Approach of Process Intensification in Biorefinery Through Reactive Extraction Coupled with Regeneration for Recovery of Protocatechuic Acid.

In the current scenario, where environmental degradation, global climate change, and the depletion of petroleum feedstock pose significant challenges, the chemical industry seeks sustainable alternatives for manufacturing chemicals, fuels, and bioplastics. Biorefining processes that integrate biomass conversion and microbial fermentation have emerged as preferred approaches to create value-added compounds. However, commercializing biorefinery products is hindered by dilute concentrations of final products and the demand for high purity goods. To address these challenges, effective separation and recovery procedures are essential to minimize costs and equipment size. This article proposes a biorefinery route for the production of protocatechuic acid (PCA) by focusing on in situ PCA separation and purification from fermentation broth. PCA is a significant phenolic molecule with numerous applications in the pharmaceutical sector for its anti-inflammatory, antiapoptotic, and antioxidant properties, as well as in the food, polymer, and other chemical industries. The chemical approach is predominantly used to produce PCA due to the cost-prohibitive nature of natural extraction techniques. Reactive extraction, a promising technique known for its enhanced extraction efficiency, is identified as a viable strategy for recovering carboxylic acids compared to conventional methods. The extraction of PCA has been explored using various solvents, including natural and conventional solvents, such as aminic and organophosphorous extractants, as well as the potential utilization of ionic liquids as green solvents. Additionally, back extraction techniques like temperature swing and diluent composition swing can be employed for reactive extraction product recovery, facilitating the regeneration of the extractant from the organic phase. By addressing the challenges associated with PCA production and usage, particularly through reactive extraction, this proposed biorefinery route aims to contribute to a more sustainable and environmentally friendly chemical industry. The incorporation of PCA in the biorefinery process allows for the utilization of this valuable compound with diverse industrial applications, thus providing an additional incentive for the development and optimization of efficient separation techniques.

Sugar profiles modulation of mangoes during osmotic dehydration in agave syrup solutions.

Chemical interaction and multicompound competition were investigated on solids gain and carbohydrate profiles evolution during osmotic dehydration of mangoes. Tommy Atkins mango slices (0.4cm and 1.5cm thickness) were osmotically processed at 40°C for up to 4h and 8h, respectively. Osmotic solutions (60 °Brix) were separated in two categories: single solute (sucrose, glucose, fructose) and multisolute (agave syrup, alone or with additions of 5% inulin or 0.1-0.3% xanthan gum) solutions. High performance liquid chromatography (HPLC) analysis was carried out on treated mango to determine sugar profiles evolution during osmotic dehydration and final product concentrations. Findings pointed out that composition of osmotic solution may modulate mango sugar profiles by triggering uptake or loss of sugar according to different phenomena: chemical potential gradient, lixiviation, prevailing mass transfer, formation of carbohydrate barrier, and solution viscosity. Mango was enriched with the solute present in the single solute osmotic solution, while it lost its own native sugars, which were absent in the osmotic solution. Increasing sample thickness reduces individual sugar uptake or loss in mango treated with both single and multisolute solutions. Significant differences in mono solute solution behavior were found for sucrose due to its capability to form a sugar layer outside the surface of thicker samples, which was shown by scanning electron microscopy (SEM) images, a barrier markedly hindering the sucrose uptake or loss. Addition of polysaccharides (particularly xanthan gum) was found to have an impact of lowering mango individual sugar uptake (18-30%). Practical Application These results will help in understanding the mechanisms by which gain of individual sugars could be reduced and composition could be modulated during osmotic dehydration of fruits. Thus, the findings in this work could lead to production of low-sugar content, osmotically processed mango snacks, enriched with inulin, enhancing their dietary and marketable value.

Non-linearity of Metabolic Pathways Critically Influences the Choice of Machine Learning Model.

The use of machine learning (ML) in life sciences has gained wide interest over the past years, as it speeds up the development of high performing models. Important modeling tools in biology have proven their worth for pathway design, such as mechanistic models and metabolic networks, as they allow better understanding of mechanisms involved in the functioning of organisms. However, little has been done on the use of ML to model metabolic pathways, and the degree of non-linearity associated with them is not clear. Here, we report the construction of different metabolic pathways with several linear and non-linear ML models. Different types of data are used; they lead to the prediction of important biological data, such as pathway flux and final product concentration. A comparison reveals that the data features impact model performance and highlight the effectiveness of non-linear models (e.g., QRF: RMSE = 0.021 nmol·min−1 and R2 = 1 vs. Bayesian GLM: RMSE = 1.379 nmol·min−1 R2 = 0.823). It turns out that the greater the degree of non-linearity of the pathway, the better suited a non-linear model will be. Therefore, a decision-making support for pathway modeling is established. These findings generally support the hypothesis that non-linear aspects predominate within the metabolic pathways. This must be taken into account when devising possible applications of these pathways for the identification of biomarkers of diseases (e.g., infections, cancer, neurodegenerative diseases) or the optimization of industrial production processes.

Digital Twins for scFv Production in Escherichia coli

Quality-by-Design (QbD) is demanded by regulatory authorities in biopharmaceutical production. Within the QbD frame advanced process control (APC), facilitated through process analytical technology (PAT) and digital twins (DT), plays an increasingly important role as it can help to assure to stay within the predefined proven acceptable range (PAR).This ensures high product quality, minimizes failure and is an important step towards a real-time-release testing (RTRT) that could help to accelerate time-to-market of drug substances, which is becoming even more important in light of dynamical pandemic situations. The approach is exemplified on scFv manufacturing in Escherichia coli. Simulation results from digital twins are compared to experimental data and found to be accurate and precise. Harvest is achieved by tangential flow filtration followed by product release through high pressure homogenization and subsequent clarification by tangential flow filtration. Digital twins of the membrane processes show that shear rate and transmembrane pressure are significant process parameters, which is in line with experimental data. Optimized settings were applied to 0.3 bar and a shear rate of 11,000 s−1. Productivity of chromatography steps were 5.3 g/L/d (Protein L) and 2167 g/L/d (CEX) and the final product concentration was 8 g/L. Based on digital twin results, an optimized process schedule was developed that decreased purification time to one working day, which is a factor-two reduction compared to the conventional process schedule. This work presents the basis for future studies on advanced process control and automation for biologics production in microbials in regulated industries.

Prospective study of the cytokine profile and antioxidant status of patients with pyoderma

Background. The importance of studying the pathogenetic features of pyoderma associated with Streptococcus pyogenes is associated with the severity of the course of the disease, frequent relapses with a short inter-relapse period, and long-term disability.The severity of the course, long-term disability, violations of the pro-oxidate mechanisms recorded in patients with poidermias associated with Streptococcus pyogenes are priority and timely.
 Aims. Study of the cytokine, prooxidant and antioxidant profiles of patients with pyoderma associated with Streptococcus pyogenes.
 Мethods. А prospective study of the cytokine profile, the level of antioxidant defense enzymes, and lipid peroxidation factors in patients with pyoderma, lasting more than 2 years, associated with Streptococcus pyogenes, was carried out. The study included 100 people with diffuse lesions of smooth skin, identified on the skin surface of Streptococcus pyogenes, at the age of 28.76 6.24 years; in blood serum, the content of cytokines IL-2, IL-8, IL-10, TNF-, IFN-, IL-1 was studied by enzyme immunoassay, in whole blood the content of primary, secondary and final products of lipid peroxidation, antioxidant enzymes protection superoxide dismutase and catalase.
 Results. Analysis of the content of cytokines showed a significant decrease in the concentration of IL-2, an increase in IL-10, TNF-, IL-8, IL-1 in the blood serum of patients with streptoderma compared with the reference values of healthy people (p 0.05). In whole blood plasma, an increase in the concentration of primary, secondary and final products of lipid peroxidation was registered with a significant decrease in the activity of antioxidant enzymes of superoxide dismutase and catalase relative to the indicators of healthy volunteers (p 0.05).
 Conclusions. In patients with streptoderma, an increase in the production of cytokines with pro-inflammatory and chemotactic properties in response to the invasion of the pathogen and its persistence was revealed. The intracellular nature of the parasitization of Streptococcus pyogenes contributes to the enhancement of the systemic and local inflammatory process, the formation of oxidative stress, the accumulation of primary, secondary and final products of lipid peroxidation, and a decrease in the activity of antioxidant enzymes. A decrease in the content of interleukin 2, which has immunoregulatory properties in patients with streptoderma, leads to impaired immune homeostasis, a decrease in the processes of differentiation in the direction of the Th1 immune response, proliferation of T-lymphocytes, a violation of the qualitative and quantitative composition of the main subpopulations of peripheral blood lymphocytes, which is clinically expressed in this occurrence of relapses in categories of patients.

Agr Quorum Sensing influences the Wood-Ljungdahl pathway in Clostridium autoethanogenum

Acetogenic bacteria are capable of fermenting CO2 and carbon monoxide containing waste-gases into a range of platform chemicals and fuels. Despite major advances in genetic engineering and improving these biocatalysts, several important physiological functions remain elusive. Among these is quorum sensing, a bacterial communication mechanism known to coordinate gene expression in response to cell population density. Two putative agr systems have been identified in the genome of Clostridium autoethanogenum suggesting bacterial communication via autoinducing signal molecules. Signal molecule-encoding agrD1 and agrD2 genes were targeted for in-frame deletion. During heterotrophic growth on fructose as a carbon and energy source, single deletions of either gene did not produce an observable phenotype. However, when both genes were simultaneously inactivated, final product concentrations in the double mutant shifted to a 1.5:1 ratio of ethanol:acetate, compared to a 0.2:1 ratio observed in the wild type control, making ethanol the dominant fermentation product. Moreover, CO2 re-assimilation was also notably reduced in both hetero- and autotrophic growth conditions. These findings were supported through comparative proteomics, which showed lower expression of carbon monoxide dehydrogenase, formate dehydrogenase A and hydrogenases in the ∆agrD1∆agrD2 double mutant, but higher levels of putative alcohol and aldehyde dehydrogenases and bacterial micro-compartment proteins. These findings suggest that Agr quorum sensing, and by inference, cell density play a role in carbon resource management and use of the Wood-Ljungdahl pathway as an electron sink.

Enzyme-photo-coupled catalysis in gas-sprayed microdroplets.

Enzyme-photo-coupled catalysis produces fine chemicals by combining the high selectivity of an enzyme with the green energy input of sunlight. Operating a large-scale system, however, remains challenging because of the significant loss of enzyme activity caused by continuous illumination and the difficulty in utilizing solar energy with high efficiency at large scale. We present a large-scale enzyme-photo-coupled catalysis system based on gas-sprayed microdroplets. By this means, we demonstrate a 43.6–71.5 times improvement of solar energy utilization over that using a traditional bulk processing system. Owing to the improved enzyme activity in microdroplets, we show that chiral alcohols can be produced with up to a 2.2-fold increase in the reaction rate and a 5.6-fold increase in final product concentration.

Development of a continuous aqueous two-phase flotation process for the downstream processing of biotechnological products

• Process intensification by ATPF as downstream for biotechnological products. • High initial product concentration leads to high final product concentration. • Main mass transfer during first 30 min of batch ATPF. • 2.5 times the volume purified by continuous ATPF compared to batch ATPF. Aqueous two-phase flotation (ATPF) is an alternative downstream process for direct recovery of biotechnological products from crude biosuspensions. ATPF is a combination of two phase extraction and flotation, resulting in high recoveries and product concentrations. In addition to selecting a suitable two-phase system, the process design must be optimized to realize an efficient ATPF process. In this study, the focus was on the process strategy. As an example of a biotechnological product, the technical enzyme phospholipase was purified. The influence of different initial enzyme concentrations on the separation process was investigated and limitations of the separation efficiency were identified. Based on these findings, batch ATPF was transferred first to semicontinuous ATPF and later to continuous ATPF. Thus, this work describes for the first time a continuous ATPF, which showed 2.5 times the purification capacity of batch ATPF in the same flotation time.

Biotransformation of Flavonoids by Newly Isolated and Characterized Lactobacillus pentosus NGI01 Strain from Kimchi.

Lactic acid bacteria (LAB) are generally recognized as safe (GRAS) microorganisms. This study aimed to identify novel LAB strains that can transform flavonoids into aglycones to improve bioavailability. We isolated 34 LAB strains from kimchi. The biotransformation activity of these 34 LAB strains was investigated based on α-L-rhamnosidase and β-D-glucosidase activities. Among them, 10 LAB strains with high activities were identified by 16S rRNA sequencing analysis. All tested LAB strains converted hesperidin to hesperetin (12.5–30.3%). Of these, only the Lactobacillus pentosus NGI01 strain produced quercetin from rutin (3.9%). The optimal biotransformation conditions for the L. pentosus NGI01 producing hesperetin and quercetin were investigated. The highest final product concentrations of hesperetin and quercetin were 207 and 78 μM, respectively. Thus, the L. pentosus NGI01 strain can be a biocatalyst for producing flavonoid aglycones in the chemical and food industries.

Manifestation of oxidative stress during pregnancy in women with chronic diseases of hepatobiliary system against the background of reproductive losses

In the early stages of gestation the changes in the lipid peroxidation can lead to violations of regulatory and protective functions of biomembranes in pregnant women. The objective: to study the changes in the concentration of intermediate and final products of LPO during the first trimester of gestation in patients with early miscarriage against the background of chronic diseases of the hepatobiliary system. Materials and methods. 118 pregnant women in the first trimester of gestation (7-10 weeks), aged 22 - 39 y. o. (mean age 29.4 ± 2.7 years) have been examined.64 women (54.2%) were diagnosed with a risk of miscarriage, and 17 patients were diagnosed with involuntary miscarriage within 10-12 days. All women were diagnosed with non-viral and non-alcoholic chronic HBS paathology: hepatic steatosis had 38 patients (32.2%), 80 patients (67.8%) had non-alcoholic steatohepatitis; in 97 patients (82.2%) chronic non-calculous cholecystitis was diagnosed. The state of lipid peroxidation was assessed by the content of malonic dialdehyde spectrophotometrically, as well as diene conjugates in the blood The indicator of erythrocyte peroxide hemolysis was examined by the level of erythrocyte peroxide resistance. Results. A significant increase in intermediate and final products of lipid peroxidation in pregnant women with an unfavorable premorbid background in the form of chronic diseases of the hepatobiliary system and a history of reproductive losses. A significant increase of MDA and DC concentration was found at the risk of premature termination of pregnancy. The degree of PLO processes activation makes these parameters integrative criteria for the detection of systemic metabolic disorders during gestation in women with GBS extragenital pathology. Conclusion. During physiological pregnancy there is an accumulation of metabolites of lipid peroxidation, which is associated with an increase in basic metabolism in women and an increase in oxygen consumption from the blood.

Process Engineering of the Acetone-Ethanol-Butanol (ABE) Fermentation in a Linear and Feedback Loop Cascade of Continuous Stirred Tank Reactors: Experiments, Modeling and Optimization

The production of butanol, acetone and ethanol by Clostridium acetobutylicum is a biphasic fermentation process. In the first phase the carbohydrate substrate is metabolized to acetic and butyric acid, in the following second phase the product spectrum is shifted towards the economically interesting solvents. Here we present a cascade of six continuous stirred tank reactors (CCSTR), which allows performing the time dependent metabolic phases of an acetone-butanol-ethanol (ABE) batch fermentation in a spatial domain. Experimental data of steady states under four operating conditions—with variations of the pH in the first bioreactor between 4.3 and 5.6 as well as the total dilution rate between 0.042 h−1 and 0.092 h−1—were used to optimize and validate a corresponding mathematical model. Beyond a residence time distribution representation and substrate, biomass and product kinetics this model also includes the differentiation of cells between the metabolic states. Model simulations predict a final product concentration of 8.2 g butanol L−1 and a productivity of 0.75 g butanol L−1 h−1 in the CCSTR operated at pHbr1 of 4.3 and D = 0.092 h−1, while 31% of the cells are differentiated to the solventogenic state. Aiming at an enrichment of solvent-producing cells, a feedback loop was introduced into the cascade, sending cells from a later state of the process (bioreactor 4) back to an early stage of the process (bioreactor 2). In agreement with the experimental observations, the model accurately predicted an increase in butanol formation rate in bioreactor stages 2 and 3, resulting in an overall butanol productivity of 0.76 g L−1 h−1 for the feedback loop cascade. The here presented CCSTR and the validated model will serve to investigate further ABE fermentation strategies for a controlled metabolic switch.

Barwniki karmelowe w świetle badań naukowych, ze szczególnym uwzględnieniem ich toksyczności

Streszczenie Barwniki karmelowe to jedne z najbardziej rozpowszechnionych na świecie dodatków do żywności, które podzielono na cztery klasy (I–IV), oznaczone odpowiednio symbolami E150 a-d. Poszczególne klasy karmeli różnią się właściwościami fizyko-chemicznymi oraz sposobem otrzymywania, co wpływa na powstawanie różnych związków, istotnych dla oceny bezpieczeństwa żywności. Przeprowadzono wiele badań wszystkich klas karmeli, w tym badania toksykokinetyczne, genotoksyczne, rakotwórcze oraz badania toksyczności reprodukcyjnej i rozwojowej, które nie wykazały ich szkodliwości, w dawkach nieprzekraczających ADI. Rośnie jednak liczba doniesień naukowych o możliwym działaniu toksycznym, obecnych w karmelach związków niskocząsteczkowych. Obecnie za ważne z toksykologicznego punktu widzenia oraz ze względu na możliwe stężenie w produkcie końcowym, uznaje się trzy związki: 5-HMF (występujący we wszystkich klasach), 4(5)-MeI (obecny w karmelu klasy III i IV) czy THI (obecny w karmelu klasa III). 4(5)-MeI działa neurotoksycznie, a w 2011 r. został uznany za związek o możliwym działaniu rakotwórczym dla człowieka (klasa 2B, wg IARC). W przypadku THI badania potwierdziły jego aktywność limfopeniczną, prawdopodobnie wtórną do działania immunosupresyjnego. W latach 80. ub. w. JECFA ustalił dopuszczalne stężenia 4(5)-MeI oraz THI w odniesieniu do klas karmeli, w których związki te mogą występować. Toksyczność 5-HMF nie została jednoznacznie potwierdzona, ale przeprowadzone badania wskazują, że związek ten nie jest obojętny dla organizmów żywych. Obecnie większość organizacji międzynarodowych i instytutów naukowych, uznaje te dodatki za bezpieczne dla konsumentów, ale jednocześnie naukowcy podkreślają potrzebę prowadzenia dalszym badań. Celem pracy jest przegląd dostępnego piśmiennictwa i doniesień dotyczących karmeli ze szczególnym uwzględnieniem ich charakterystyki toksykologicznej.

Gas-phase isopropanol degradation by nonthermal plasma combined with Mn-Cu/-Al2O3.

In this study, the dielectric barrier discharge (DBD) induced by nonthermal plasma (NTP) technology was used for isopropanol (IPA) degradation. IPA, intermediate, final product, and ozone concentrations were analyzed using GC-MS, carbon dioxide detector, and ozone detector. The experimental flow rate and concentration were fixed to 1 L/min and 1200 ppm ± 10%, respectively. Different reaction procedures were proposed for self-made metal catalyst combined with a plasma system (plasma alone and γ-Al2O3 combined with plasma, Cu (5 wt%)/γ-Al2O3 combined with plasma, Mn (3 wt%)-Cu (5 wt%)/γ-Al2O3 combined with plasma). In addition, the effect of the carrier gas oxygen content (0%, 20%, and 100%) on IPA conversion and intermediate and carbon dioxide selectivity was also investigated. The results revealed that the Mn (F)-Cu/γ-Al2O3 combined with plasma exhibited more efficient IPA conversion. In the 100% oxygen environment, the IPA conversion rate increased from 79.32 to 99.99%, and carbon dioxide selectivity increased from 3.82 to 50.23%. IPA was completely converted after 60 min of plasma treatment with the acetone selectivity, carbon dioxide selectivity, and tail ozone concentration of 26.71% ± 1.27%, 50.23% ± 0.56%, and 1761 ± 11 ppm, respectively. This study proved that the current single planar DBD configuration is an effective advanced treatment technology for the decomposition of VOCs.

Understanding Catalysis—A Simplified Simulation of Catalytic Reactors for CO2 Reduction

The realistic numerical simulation of chemical processes, such as those occurring in catalytic reactors, is a complex undertaking, requiring knowledge of chemical thermodynamics, multi-component activated rate equations, coupled flows of material and heat, etc. A standard approach is to make use of a process simulation program package. However for a basic understanding, it may be advantageous to sacrifice some realism and to independently reproduce, in essence, the package computations. Here, we set up and numerically solve the basic equations governing the functioning of plug-flow reactors (PFR) and continuously stirred tank reactors (CSTR), and we demonstrate the procedure with simplified cases of the catalytic hydrogenation of carbon dioxide to form the synthetic fuels methanol and methane, each of which involves five chemical species undergoing three coupled chemical reactions. We show how to predict final product concentrations as a function of the catalyst system, reactor parameters, initial reactant concentrations, temperature, and pressure. Further, we use the numerical solutions to verify the “thermodynamic limit” of a PFR and a CSTR, and, for a PFR, to demonstrate the enhanced efficiency obtainable by “looping” and “sorption-enhancement”.

An innovative route for the production of atorvastatin side-chain precursor by DERA-catalysed double aldol addition

A multi-enzyme route for the production of an atorvastatin side-chain was proposed. The approach includes the consecutive double aldol addition of acetaldehyde to the phenylacetamide amino-protected propanal by 2-deoxyribose-5-phosphate aldolase (DERA), the oxidation by ketoreductase, the lipase-catalysed acylation and amino group deprotection by penicillin G-acylase. To explore the feasibility of the process, the DERA reaction was studied into detail. Based on the kinetic and stability studies, a mathematical model was developed and validated in a batch and fed-batch reactor. The highest productivity was obtained in repetitive batch reactor (229.1 g/(L day)). The highest final product concentration of 124 g/L was obtained in fed-batch reactor. The mathematical model-based optimisation provided insight into the possibilities for process metrics improvement. Further, the second step was explored. The results showed that the DERA reaction and the oxidation reaction can be carried out as the multi-enzyme one pot process in the sequential manner.