High Molar Yields Research Articles

Sustainable production 3-bromobutyrates and 3-hydroxybutyrates from bioderived poly-3-hydroxybutyrate

The efficient and effective degradation of bio-polymer poly-3-hydroxybutyrate (PHB) has emerged as a prominent research focus. In this investigation, we explored the valorization of PHB to 3-bromobutyrates and 3-hydroxybutyrates employing hydrogen bromide (HBr) as a catalyst at relatively mild temperatures (70–110 °C). Comprehensive investigations were conducted on reaction solvent systems (HBr solution and HBr-HAc (acetic acid) solution) along with process parameters. The impact of these variables is systematically assessed using JMP13 software. In the HBr solution, both 3-hydroxybutyric acid (3HA) and 3-bromobutyric acid (3BA) are identified as the primary products. Remarkably, a high 3HA yield of up to 96.3 mol% is achieved at 70 °C, while the 3BA yield remains below 52 mol% within the tested temperature range. Conversely, the HBr-HAc solution yields a favorable 3BA (>99 mol%). Furthermore, we demonstrate a strategy for synthesizing various 3-bromobutyrates through a tandem degradation-esterification process. The utilization of HBr catalysis presents compelling advantages, including a straightforward process conducted under mild conditions, facilitating the complete degradation of PHB into the desired target products with notably high molar yields.

Experimental Study of Bio-Hydrogen Production by Clostridium beijerinckii from Different Substrates

Glucose, alcohol stillage and glycerol were used as substrates for bio-hydrogen production by the newly isolated strain Clostridium beijerinckii 6A1 under batch conditions. High molar yields of hydrogen from the studied organic substrates were observed. There was a neat difference in the metabolic pathways of substrate digestion when hexose-based substrate or glycerol were used. The products of glycerol digestion showed that a pathway with no formic acid formation as intermediate was probable. In this case, considerable concentrations of acetic and propionic acid (up to 6 g dm−3) and small amounts of butanol were observed after 48 h. When glucose or hexose-based substrates were used, considerable amounts of formic acid (up to 6 g dm−3), i.e., the pathway proposed for Clostridia mixed cultures, were appropriate for the observed process of hydrogen release. For these substrates, considerable amounts of propionic acid in concentrations up to 1 g dm−3 were observed. That is why the pathway proposed for mixed cultures seemed more appropriate for our experiments carried out with hexose-based substrates. When hexoses were used, substrate digestion stopped the formation of acetic acid, propionic acid and ethanol. Probably, these intermediates are inhibitors to the further digestion to other products.

Bioconversion of ferulic acid and vanillin to vanillic acid by cold-adapted Paraburkholderia aromaticivorans AR20-38: impact of culture conditions

PurposeBiovalorization of lignin-derived aromatic monomers such as ferulic acid (FA) has attracted considerable interest. The cold-adapted strain Paraburkholderia aromaticivorans AR20-38 converts FA to the value-added product vanillic acid (VA), without further VA degradation. The efficiency of the bioconversion of FA to VA was optimized by studying culture conditions.MethodsVarious cultivation parameters (agitation, temperature, FA concentration, nutrient supplementation) were assessed to increase biomass production and shorten the cultivation time, while obtaining high VA production yields. The fate of the intermediate vanillin was also studied. Lignin monomers and degradation products (FA, vanillin, VA) were quantified via UV/Vis-HPLC.ResultFull bioconversion of 5 mM FA occurred over a broad temperature range of 5–30 °C. Concentrations up 30 mM FA were utilized as the sole carbon source at 20 °C. Molar VA yields (> 90%) produced from 5 to 12.5 mM FA and from 15 to 17.5 mM FA (82–87%) were not significantly different at 10 °C and 20 °C. The supplementation of the mineral medium with monosaccharides (glucose, fructose, mannose) and/or N-rich complex compounds (yeast extract, casamino acids) resulted in high biomass production, accelerated FA bioconversion, and high molar yields (96–100%). The presence of the N-rich compounds alone or in combination with glucose reduced the incubation time necessary to convert FA to VA. Vanillin, formed as an intermediate during FA degradation, was consumed and converted to VA before FA metabolization, when added in combination with FA. Vanillin bioconversion was significantly accelerated in the presence of glucose.ConclusionThe variation of culture conditions improved the efficiency of the studied strain to convert FA via vanillin to VA and demonstrated remarkable FA bioconversion under varying environmental conditions, especially temperature, substrate concentration, and nutrient availability, which is of importance for potential future application.

An artificial multi-enzyme cascade biocatalysis for biomanufacturing of nicotinamide mononucleotide from starch and nicotinamide in one-pot

β-Nicotinamide mononucleotide (NMN) is an important precursor in the synthesis of nicotinamide adenine dinucleotide (NAD+) and confers multiple health benefits, resulting in the rapid growth of NMN market capacity in the fields of food and health care. To overcome the drawbacks of NMN production by the existing chemical or microbial fermentation method, there is an urgent need to develop a prospective NMN production strategy with low cost, low pollution, and high yield. In this study, we demonstrated an artificial in vitro multi-enzyme cascade biocatalysis using starch and nicotinamide (Nam) as substrates for the synthesis of NMN in one-pot. This multi-enzyme cascade reaction was optimized in terms of pH value, buffer concentration, inorganic phosphate concentration, enzyme composition, and phosphoenolpyruvate concentration. Under optimized conditions, a high molar yield of 87.8% for NMN was achieved using 3.2 mM Nam as substrate, and a molar yield of 55.37% for NMN was also achieved under the initial Nam concentration of 9.21 mM. This in vitro enzymatic platform provides an environmental friendliness biomanufacturing technology for the production of NMN, showing a highly promising alternative approach for NMN production.

Multiphase Ozonolysis of Oleic Acid-Based Lipids: Quantitation of Major Products and Kinetic Multilayer Modeling.

Commonly found in atmospheric aerosols, cooking oils, and human sebum, unsaturated lipids rapidly decay upon exposure to ozone, following the Criegee mechanism. Here, the gas-surface ozonolysis of three oleic acid-based compounds was studied in a reactor and indoors. Under dry conditions, quantitative product analyses by 1H NMR indicate up to 79% molar yield of stable secondary ozonides (SOZs) in oxidized triolein and methyl oleate coatings. Elevated relative humidity (RH) significantly suppresses the SOZ yields, enhancing the formation of condensed-phase aldehydes and volatile C9 products. Along with kinetic parameters informed by molecular dynamics simulations, these results were used as constraints in a kinetic multilayer model (KM-GAP) simulating triolein ozonolysis. Covering a wide range of coating thicknesses and ozone levels, the model predicts a much faster decay near the gas-lipid interface compared to the bulk. Although the dependence of RH on SOZ yields is well predicted, the model overestimates the production of H2O2 and aldehydes. With negligible dependence on RH, the product composition for oxidized oleic acid is substantially affected by a competitive reaction between Criegee intermediates (CIs) and carboxylic acids. The resulting α-acyloxyalkyl hydroperoxides (α-AAHPs) have much higher molar yields (29-38%) than SOZs (12-16%). Overall, the ozone-lipid chemistry could affect the indoor environment through "crust" accumulation on surfaces and volatile organic compound (VOC) emission. In the atmosphere, the peroxide formation and changes in particle hygroscopicity may have effects on climate. The related health impacts are also discussed.

Tuning a bi-enzymatic cascade reaction in Escherichia coli to facilitate NADPH regeneration for \u03b5-caprolactone production

ε-Caprolactone is a monomer of poly(ε-caprolactone) which has been widely used in tissue engineering due to its biodegradability and biocompatibility. To meet the massive demand for this monomer, an efficient whole-cell biocatalytic approach was constructed to boost the ε-caprolactone production using cyclohexanol as substrate. Combining an alcohol dehydrogenase (ADH) with a cyclohexanone monooxygenase (CHMO) in Escherichia coli, a self-sufficient NADPH-cofactor regeneration system was obtained. Furthermore, some improved variants with the better substrate tolerance and higher catalytic ability to ε-caprolactone production were designed by regulating the ribosome binding sites. The best mutant strain exhibited an ε-caprolactone yield of 0.80 mol/mol using 60 mM cyclohexanol as substrate, while the starting strain only got a conversion of 0.38 mol/mol when 20 mM cyclohexanol was supplemented. The engineered whole-cell biocatalyst was used in four sequential batches to achieve a production of 126 mM ε-caprolactone with a high molar yield of 0.78 mol/mol.

Fuel-grade sunflower oil butyl esters: synthesis, purification, oxidation stability

Current paper deals with production, purification and oxidative stability enhancement of fuel-grade sunflower oil butyl esters as more ecological alternative of methyl esters as biodiesel. The oil feedstock, used in this study, included refined sunflower oil (acid value – 0.05 mg KOH/g; 25.3 % of oleic and 61.2 % of linoleic acids) and wasted frying high-oleic sunflower oil (acid value – 1.20 mg KOH/g; 6.1 % of linoleic and 81.7 % of oleic acids). Butanolysis was carried out using potassium butoxide, obtained from KOH and alcohols via original patent-pending method, under mild reaction conditions (alcohol-to-oil molar ratio – 4.5-5.0, 15°C, 1.4-1.6 %еq. KOH of butoxide, 20-30 min). High molar yield of butyl esters (93-96 %) was achieved, while glycerol and vast majority of alkaline catalyst formed the separate reaction products phase mainly in the course of reaction. Ester enriched phases were purified in order to obtain fuel-grade butanol-based biodiesel. Samples after removing of butanol under vacuum followed by water washing and drying were characterized by not enough high butyl esters content (about 94-95 %), as well as higher than allowed content of unconverted glycerides. Vacuum distillation as final purification step allowed fitting butyl esters samples composition within the requirements for biodiesel fuel. Distilled samples contained about 99 % of butyl esters, 0.4-0.5 % of monoglycerides and almost no n-butanol, glycerol, di- and triglycerides. Oxidative treatment (110°C, 6 h, air bubbling) revealed the high oxidation stability of the sample, originated from wasted high-oleic oil, due to the predominance of oleic acid in its fatty acid composition. The sample, obtained from refined sunflower oil (mainly linoleic acid in fatty acid composition), demonstrated very low stability. Addition of at least 2000 mg/kg of antioxidant 2,6-di-tert-butyl-4-methylphenol was shown to be able to improve this characteristic to the level of biodiesel requirements.

N-nitrosodimethylamine formation potential (NDMA-FP) of ranitidine remains after chlorination and/or photo-irradiation: Identification of transformation products in combination with NDMA-FP test

N-nitrosodimethylamine (NDMA), a probable carcinogenic disinfection by-product, can be formed with high molar yields following chloramination of ranitidine (RNTD), a histamine H2-receptor antagonist. Although RNTD and some of its transformation products (TPs) have been studied under chlorination and photo-irradiation, the relationship between RNTD TPs and NDMA formation potential (NDMA-FP) remaining after those processes is still unclear. This study investigated the effects of chlorination and/or photo-irradiation on NDMA-FP derived from RNTD, simulating an urban water environment receiving treated wastewater. After chlorination and/or photo-irradiation of RNTD, ten TPs including five new ones were identified by liquid chromatography–quadrupole time-of-flight mass spectrometry (LC-QTof-MS). In addition, important RNTD TPs responsible for NDMA-FP (e.g., chlorinated and hydroxylated RNTD: TP-364) were also confirmed by the relationship between detected peak area and NDMA-FP. The results showed that NDMA-FP remained due to the presence of RNTD TPs, although RNTD itself was significantly removed by chlorination and/or photo-irradiation. TP-364 was only formed by chlorination of RNTD and could not be removed by photo-irradiation. TP-314 (a stereoisomer of RNTD), -299, and -286, which were mainly formed by photo-irradiation of RNTD but not by photo-irradiation after chlorination, had strong positive correlations with NDMA-FP (R2 > 0.90; F-test, P < 0.01).

Online measurement of dissolved oxygen in shake flask to elucidate its role on caffeine degradation by Pseudomonas sp.

ABSTRACT Caffeine is a plant alkaloid present in the large ratio over other emerging pollutants and it causes serious health effects on overdosage. Microbial degradation of caffeine produces metabolites that can be used as a multi-functional drug. In this study, the effect of dissolved oxygen (DO) on microbial growth and degradation of caffeine in minimal media, synthetic coffee effluent treatment, and theobromine production was studied in presens flask – SFR vario installed in an orbital shaker. Induction studies showed Pseudomonas sp. requires oxygen for caffeine degradation. Theobromine production with induced cells of Pseudomonas sp. showed maximum accumulation of 35 mg/l with a higher molar yield of 80% at higher DO of 60% saturation when compared to experiments done with a lower oxygen level of 25% and 20% saturation. Effluent treatment using induced cells was the fastest caffeine degradation ever reported at 0.055 g/l.h with 0.4 g/l of induced cell concentration without affecting the polyphenol content significantly. Higher DO in the medium is required for efficient conversion of caffeine to theobromine which is in agreement that the reaction is oxidative demethylation. Online monitoring of DO is very important in shake flask studies which will be useful in scaling up processes.

Thermostable arginase from Sulfobacillus acidophilus with neutral pH optimum applied for high-efficiency L-ornithine production.

This study aims to use neutral pH optimum arginase as the catalyst for high-efficiency L-ornithine production. Sulfobacillus acidophilus arginase was firstly cloned and overexpressed in Escherichia coli. The purified enzyme was obtained, and the molecular mass determination showed that this arginase was a hexamer. S. acidophilus arginase possessed similarities with the other arginases such as the conserved sequences, purification behavior, and the necessity for Mn2+ as a cofactor. The maximum enzyme activity was obtained at pH7.5 and 70°C. Thermostability and pH stability analysis showed that the arginase was stable at 30-60°C and pH7.0-8.5, respectively. The kinetic parameters suggested that S. acidophilus arginase could efficiently hydrolyze L-arginine. Bioconversion with this neutral pH optimum arginase had the advantages of avoiding producing by-product, high molar yield, and high-level production of L-ornithine. When the bioconversion was performed with a fed-batch strategy and a coupled-enzyme system involving S. acidophilus arginase and Jack bean urease, the final production of 2.87mol/L was obtained with only 1.72mmol/L L-arginine residue, and the molar yield was 99.9%. The highest production record suggests that S. acidophilus arginase has a great prospect in industrial L-ornithine production.

One-Pot Alcoholysis of the Lignocellulosic Eucalyptus nitens Biomass to n-Butyl Levulinate, a Valuable Additive for Diesel Motor Fuel

The present investigation represents a concrete example of complete valorization of Eucalyptus nitens biomass, in the framework of the circular economy. Autohydrolyzed-delignified Eucalyptus nitens was employed as a cheap cellulose-rich feedstock in the direct alcoholysis to n-butyl levulinate, adopting n-butanol as green reagent/reaction medium, very dilute sulfuric acid as a homogeneous catalyst, and different heating systems. The effect of the main reaction parameters to give n-butyl levulinate was investigated to check the feasibility of this reaction and identify the coarse ranges of the main operating variables of greater relevance. High n-butyl levulinate molar yields (35–40 mol%) were achieved under microwave and traditional heating, even using a very high biomass loading (20 wt%), an eligible aspect from the perspective of the high gravity approach. The possibility of reprocessing the reaction mixture deriving from the optimized experiment by the addition of fresh biomass was evaluated, achieving the maximum n-butyl levulinate concentration of about 85 g/L after only one microwave reprocessing of the mother liquor, the highest value hitherto reported starting from real biomass. The alcoholysis reaction was further optimized by Response Surface Methodology, setting a Face-Centered Central Composite Design, which was experimentally validated at the optimal operating conditions for the n-butyl levulinate production. Finally, a preliminary study of diesel engine performances and emissions for a model mixture with analogous composition to that produced from the butanolysis reaction was performed, confirming its potential application as an additive for diesel fuel, without separation of each component.

Expression and Characterization of a Bright Far-red Fluorescent Protein from the Pink-Pigmented Tissues of Porites lobata.

Members of the anthozoan green fluorescent protein (GFP) family display a diversity of photo-physical properties that can be associated with normal and damaged coral tissues. Poritid coral species often exhibit localized pink pigmentation in diseased or damaged tissues. Our spectral and histological analyses of pink-pigmented Porites lobata lesions show co-localization of bright red fluorescence with putative amoebocytes concentrating in the epidermis, suggesting an activated innate immune response. Here we report the cloning, expression, and characterization of a novel red fluorescent protein (plobRFP) from the pink-pigmented tissues associated with lesions on Porites lobata. In vitro, the recombinant plobRFP exhibits a distinct red emission signal of 614 nm (excitation maximum: 578 nm), making plobRFP the furthest red-shifted natural fluorescent protein isolated from a scleractinian coral. The recombinant protein has a high molar extinction coefficient (84,000 M-1 cm-1) and quantum yield (0.74), conferring a notable brightness to plobRFP. Sequence analysis suggests the distinct brightness and marked red shift may be inherent features of plobRFP's chromophore conformation. While plobRFP displays a tendency to aggregate, its high pH stability, photostability, and spectral properties make it a candidate for cell imaging applications and a potential template for engineering optimized RFPs. The association of plobRFP with a possible immune response furthers its potential use as a visual diagnostic and molecular biomarker for monitoring coral health.

Bioconversion of Xylose to Ethylene Glycol and Glycolate in Engineered Corynebacterium glutamicum.

The biological production of two-carbon compounds (ethylene glycol (EG) and glycolate) has been studied for the sustainable supply of the compounds to the polymer, cosmetic, textile, and medical industries. Here, we demonstrated the bioconversion of xylose to either ethylene glycol (EG) or glycolate using engineered Corynebacterium glutamicum, a well-known industrial amino acid producer. A synthetic ribulose 1-phosphate (Ru1P) pathway involving heterologous d-tagatose 3-epimerase and l-fuculose kinase/aldolase reactions was introduced in C. glutamicum. Subsequently, heterologous expression of Escherichia coli YqhD reductase with the synthetic Ru1P pathway led to ethylene glycol production from xylose. Additional pathway engineering in C. glutamicum by mutating ald, which encodes an aldehyde dehydrogenase, abolished the by-product formation of glycolate during xylose conversion to EG at a yield of 0.75 mol per mol. In addition, the bioconversion of xylose to glycolate was achieved, and the almost maximum molar yield was 0.99 mol per mol xylose in C. glutamicum via the Ru1P pathway. Thus, the synthetic Ru1P pathway in C. glutamicum led bioconversion of xylose to either ethylene glycol or glycolate with high molar yields.

Bio-hydrogen production from tequila vinasses: Effect of detoxification with activated charcoal on dark fermentation performance

Hydrogen production from dark fermentation is a potential source of sustainable fuel when it is generated from waste. This study compared hydrogen production resulting from fermentation using raw and detoxified tequila vinasse. Vinasse was detoxified with granular activated charcoal, which was used to adsorb compounds that could inhibit the production of hydrogen by dark fermentation. In batch cultures detoxification of vinasse led to up to 20% higher maximum velocities of hydrogen production, a 5.4 h reduction in the lag phase and an 11% higher molar yield, compared to results obtained with raw vinasse. Losses of sugars after detoxification provoked that the specific hydrogen volumetric yields obtained with detoxified vinasse were 30–40% lower with 5 g COD/L and 15 g COD/L initial concentrations, compared to the ones obtained with raw vinasse. For an initial 30 g COD/L no differences in specific hydrogen yields were observed between raw or detoxified vinasse in batch fermentation. Continuous culture fermentation of vinasse showed hydrogen production rates between 1.32 ± 0.07 to 1.39 ± 0.14 NL H2/L-d when extra nutrients were added, while a stable production of hydrogen through fermentation of detoxified vinasse could not be maintained despite nutrient addition. Production of hydrogen from vinasse diluted with water with no additional nutrients was assessed and rates close to 0.42 ± 0.02 NL H2/L-d and hydrogen content close to 37% were obtained. Accumulation of lactic acid and a predominant production of butyric acid over acetic acid suggested that the fermentation dynamics of vinasse with no supplementary nutrients were especially susceptible to high substrate loading rates and prolonged hydraulic retention times.

Electrocatalytic Hydrogenation and Oxidation of 5-Hydroxymethylfurfural for Efficient Production of Biobased Monomers: A Paired Electrolyzer Approach

Electrochemical conversion of biorenewable compounds is a promising route for sustainable chemical production. Herein, we report a high efficiency for electrocatalytic conversion of 5-(hydroxymethyl)furfural (HMF) to two biobased monomers by pairing HMF reduction and oxidation reactions in a single electrochemical cell. HMF hydrogenation to 2,5-bis(hydroxymethyl)furan (BHMF) was achieved under mild electrolyte conditions (pH 9.2) over a Ag/C catalyst at the cathode. The selectivity and efficiency for Ag-catalyzed BHMF formation were sensitive to cathode potential, owing to competition from HMF hydrodimerization reactions and hydrogen evolution. Moreover, the carbon support of Ag/C was active for HMF reduction and contributed to undesired dimer formation at strong cathodic potentials. As a result, high BHMF selectivity and efficiency was only achieved within a narrow potential range near –1.3 V. At the anode, HMF oxidation to 2,5-furandicarboxylic acid (FDCA) with ~100% efficiency was achieved under the same conditions by a homogeneous redox mediator, 4-acetamido-TEMPO (ACT), together with an inexpensive carbon felt anode. Furtunately, the insensitive selectivity of ACT-mediated HMF oxidation anode potential allows HMF hydrogenation and oxidation reactions to perform together in a single electrochemical cell, which demonstrates high molar yields of BHMF and FDCA (86% and 96%, respectively) and a combined electron efficiency of 187%, which is nearly two-fold enhancement compared to the unpaired cells. Our recent progress in developing porous Ag electrode materials for electrochemical reduction will also be presented.

High yield one-pot synthesis of high density and low freezing point jet-fuel-ranged blending from bio-derived phenol and cyclopentanol

Synthesizing high performance jet fuel from biomass provides potential way to convert low-cost biomass to valuable fuels and meets the requirements of sustainable development. Here, we report a one-pot synthesis of high density and low freezing point jet-fuel-ranged blending from bio-derived phenol and cyclopentanol, which is with high yield, simple and low-cost for scale-up. With the co-presence of acid catalyst like Hβ and metal catlayst like Pd/C, the alkylation first happens to produce bi-and tri-cyclic compounds under N2 atomphere, then in H2 atmosphere the remained reactant is partly hydrogenated and takes part in alkylation again to produce cyclic compounds, finally hydrodeoxygenation happens to convert all the compounds to cyclic hydrocarbons. A jet-fuel-blending containing bi- and tri-cyclic alkanes is obtained at high molar yield of 83.9% from the starting reactant, which shows high density of 0.89 g/mL, freezing point lower than −75 °C. Especially, the major component, i.e. cyclopentylcyclohexane shows much better low-temperature properties compared with reported hydrocarbons with similar molecular structure. This result provides a simple, low-cost way to synthesize high performance jet fuel from biomass.

Biorefinery processes for the valorization of Miscanthus polysaccharides: from constituent sugars to platform chemicals

A biorefinery scheme was proposed for manufacturing platform chemicals (furfural, denoted F, and 5-hydroxymethylfurfural, denoted HMF) from Miscanthus polysaccharides (including hemicelluloses and cellulose). The feedstock was first subjected to hydrothermal processing, which caused an extensive hemicellulose solubilization, yielding solids enriched in cellulose and aqueous solutions rich in saccharides. The acidic processing of the aqueous solutions in the presence of methyl isobutyl ketone (MIBK), which acted as an extracting agent, led to the formation and the in situ separation of F from pentoses at high molar yields (up to 78%). Moreover, HMF and levulinic acid were obtained from the hexoses released from the feedstock.The cellulose-enriched solids from hydrothermal processing were used as a substrate for HMF manufacture, employing a combination of enzymatic and chemical treatments. The enzymatic hydrolysis yielded glucose (in concentration up to 59 g /L), which was enzymatically isomerized into fructose in the presence of sodium tetraborate at yields up to 80%. Acidic treatments of the resulting reaction media at low temperature (134 °C) in the presence of H2SO4 enabled the formation of HMF at yields about 49%. Under the assayed conditions, glucose remained practically unaltered, facilitating its reutilization in the isomerization stage.

Renewable diesel production by hydrothermal decarboxylation of fatty acids over platinum on carbon catalyst

For over a decade researchers have been investigating the potential to produce renewable diesel from fatty acid, possibly because it possesses good qualities such as very high cetane number, oxidative stability, and renewability, and can be produced and transported using existing refinery process facilities, making it a potential substitute for petroleum diesel. Most of these investigations required the use of organic solvents and hydrogen which might increase the cost of production. To avoid this, the current work was conducted in an aqueous medium without the addition of hydrogen, using hydrothermal decarboxylation of palmitic and oleic acids in the presence of 5% platinum on carbon catalyst. The performance of the primary products pentadecane and heptadecane obtained was optimized by determining the optimum operating conditions of temperature and residence time. The results showed that the highest molar yield of pentadecane from palmitic acid was 55.3% at the optimum conditions of 290 °C and 1.5 h, and that of heptadecane from oleic acid was 16.4% at 290 °C and 4 h. With these results the cost of production might be reduced and using a benign, environmentally friendly medium would help to reduce the risk associated with the use of organic solvents.

Stability of the Monoelectronic Reduction Product from 1,2,5‐Thiadiazole S,S‐Dioxides. Electrochemical, Chemical, and Photoinduced Doping

AbstractThe accumulation of radical anions from 3,4‐disubstituted 1,2,5‐thiadiazole S,S‐dioxides (1) in solution of organic solvents is achieved by electrochemical, chemical and photoinduced pathways. Electrolytic and chemical reduction of 1 produces the radical anions (1•–) in high molar yields (&gt; ca. 80%). The survival of 1•– is measured for ca. three months. The stability of the reduced state depends on its structure and the composition (solvent, reducing agent, and supporting electrolyte) of the medium in which it is generated by the chemical and electrochemical routes. In solution of polar aprotic solvents, 1•– persists even in the presence of water or oxygen. Irradiation with 254 nm light generates 1•– but only in DMF solution; the proposed reaction mechanism involves the participation of the solvent. Radical anions are characterized by cyclic voltammetry, UV‐Vis spectrophotometry and electron spin resonance spectroscopy. The chemical stability and the properties of 1/1•– make them suitable for the development of novel materials for technological applications.

High-yield production of 1,3-propanediol from glycerol by metabolically engineered Klebsiella pneumoniae

BackgroundGlycerol is a major byproduct of the biodiesel industry and can be converted to 1,3-propanediol (1,3-PDO) by microorganisms through a two-step enzymatic reaction. The production of 1,3-PDO from glycerol using microorganisms is accompanied by formation of unwanted byproducts, including lactate and 2,3-butanediol, resulting in a low-conversion yield.ResultsKlebsiella pneumoniae was metabolically engineered to produce high-molar yield of 1,3-PDO from glycerol. First, the pathway genes for byproduct formation were deleted in K. pneumoniae. Then, glycerol assimilation pathways were eliminated and mannitol was co-fed to the medium. Finally, transcriptional regulation of the dha operon were genetically modified for enhancing 1,3-propanediol production. The batch fermentation of the engineered strain with co-feeding of a small amount of mannitol yielded 0.76 mol 1,3-PDO from 1 mol glycerol.ConclusionsKlebsiella pneumoniae is useful microorganism for producing 1,3-PDO from glycerol. Implemented engineering in this study successfully improved 1,3-PDO production yield, which is significantly higher than those reported in previous studies.