Chemical Building Blocks Research Articles

(Invited) Taking a Closer Look at SEI Chemistry

Interphases enables the electrodes to operate at potentials beyond what thermodynamic stability limits of non-aqueous electrolytes would allow. The most prominent example of interphases is perhaps solid-electrolyte-interphase (SEI) on graphitic anodes in Li-ion batteries, which ensures the reversibility of Li-ion intercalation chemistries. In typical electrolytes, chemical building blocks of SEI mainly come from solvents decomposition products, and, although we often acknowledge that many aspects of SEI remains unknown, we thought we at least have establish the following foundation beyond doubt: (1) semi-carbonates from the single-electron reduction of carbonate solvents constitutes the major portion of SEI; (2) the formation of SEI is irreversible; and (3) SEI is ionic conductor and electron insulator. However, when taking a closer look at the “olde SEI” using a series of new techniques, we found some of those principles might need to be re-written. In this work, I will summarize the newest understanding of this “least understood” component in Li-ion battery that were achieved in my own group and my collaborators.

Macromolecular Characterization of Swordfish Oocytes by FTIR Imaging Spectroscopy

During folliculogenesis, primary oocytes of teleosts grow by several orders of magnitude by-self synthesizing proteins and mRNA, or sequestering from blood specific macromolecular components, such as fatty acids and vitellogenin. All these materials are stored into cortical alveoli, yolk globules or oil droplets during oocyte development. The proper synthesis, storage and displacement of these macromolecular components inside the oocyte play a key role for a successful fertilization process and for the subsequently correct embryo development. In this study, for the first time, the FTIR Imaging (FTIRI) spectroscopy has been applied to characterize the chemical building blocks of several cellular components of swordfish oocytes at different developmental stages. In particular, the spectral features of previtellogenic (PV), vitellogenic (VTG), mature (M) and atretic (A) follicles as well as and of cortical alveoli (CA), yolk vesicles (YV), oil droplets (OD) and Zona Radiata (ZR) have been outlined, providing new insights in terms of composition and topographical distribution of macromolecules of biological interest such as lipids, proteins, carbohydrates and phosphates. The macromolecular characterization of swordfish oocytes at different developmental stages represents a starting point and a useful tool for the assessment of swordfish egg quality caught in different conditions, such as periods of the year or different fishing area.

Efficient succinic acid production from high-sugar-content beverages by Actinobacillus succinogenes.

This study presents the production of succinic acid (SA) by Actinobacillus succinogenes using high-sugar-content beverages (HSCBs) as feedstock. The aim of this study was the valorization of a by-product stream from the beverage industry for the production of an important building block chemical, such as SA. Three types of commercial beverages were investigated: fruit juices (pineapple and ace), syrups (almond), and soft drinks (cola and lemon). They contained mainly glucose, fructose, and sucrose at high concentration-between 50 and 1,000 g/L. The batch fermentation tests highlighted that A. succinogenes was able to grow on HSCBs supplemented with yeast extract, but also on the unsupplemented fruit juices. Indeed, the bacteria did not grow on the unsupplemented syrup and soft drinks because of the lack of indispensable nutrients. About 30-40 g/L of SA were obtained, depending on the type of HSCB, with yield ranging between 0.75 and 1.00 gSA /gS . The prehydrolysis step improved the fermentation performance: SA production was improved by 6-24%, depending on the HSCB, and sugar conversion was improved of about 30-50%.

Physical–Chemical Characteristics of Cutin Separated from Tomato Waste for the Preparation of Bio-lacquers

Green chemistry protocols are proposed to produce high-value chemicals from waste tomatoes. Long-chain hydroxy fatty acids (called cutin acids), in particular the 10,16-dihydroxyhexadecanoic acid and its oligomers, could be innovative building-block chemicals for the synthesis of novel bio-resins and lacquers suitable as internal protective coating for metal food packaging. However, these natural compounds are not currently commercially available. This study investigates the possibility of extracting cutin acids from tomato peels without the use of organic solvents and by an efficient, cost-effective, and environmentally safe method amenable to industrial scale-up. The first route investigated was based on alkaline hydrolysis of the tomato cuticle. The second involved the acid free-selective precipitation of cutin. Finally, cutin was isolated by hydrogen peroxide-assisted hydrolysis. GC-MS analysis revealed the main chemical compound isolated by all methods to be 10,16-dihydroxyhexadecanoic acid, the principal component of tomato cutin, with extraction yields ranging from 81 to 96%. Products are different in terms of appearance, solubility, the degree of crosslinking observed and molecular weight, as shown by GPC analysis. Furthermore, the products extracted were characterized by means of FT-IR spectroscopy and thermal analysis. The cutin obtained through alkaline hydrolysis results the best raw material for bio-resin preparation.

Metal-Organic Framework Coating Enhances the Performance of Cu2O in Photoelectrochemical CO2 Reduction.

Photoelectrochemical (PEC) reduction of CO2 into chemical fuels and chemical building blocks is a promising strategy for addressing the energy and environmental challenges, which relies on the development of p-type photocathodes. Cu2O is such a p-type semiconductor for photocathodes but commonly suffers from detrimental photocorrosion and chemical changes. In this communication, we develop a facile procedure for coating a metal-organic framework (MOF) on the surface of a Cu2O photocathode, which can both prevent photocorrosion and offer active sites for CO2 reduction. As evidenced by ultrafast spectroscopy, the formed interface can effectively promote charge separation and transfer. As a result, both the activity and durability of Cu2O are dramatically enhanced for PEC CO2 reduction. This work provides fresh insights into the design of advanced hybrid photoelectrodes and highlights the important role of interfacial charge dynamics in PEC CO2 conversion.

Biomass-Derived Production of Itaconic Acid as a Building Block in Specialty Polymers.

Biomass, the only source of renewable organic carbon on Earth, offers an efficient substrate for bio-based organic acid production as an alternative to the leading petrochemical industry based on non-renewable resources. Itaconic acid (IA) is one of the most important organic acids that can be obtained from lignocellulose biomass. IA, a 5-C dicarboxylic acid, is a promising platform chemical with extensive applications; therefore, it is included in the top 12 building block chemicals by the US Department of Energy. Biotechnologically, IA production can take place through fermentation with fungi like Aspergillus terreus and Ustilago maydis strains or with metabolically engineered bacteria like Escherichia coli and Corynebacterium glutamicum. Bio-based IA represents a feasible substitute for petrochemically produced acrylic acid, paints, varnishes, biodegradable polymers, and other different organic compounds. IA and its derivatives, due to their trifunctional structure, support the synthesis of a wide range of innovative polymers through crosslinking, with applications in special hydrogels for water decontamination, targeted drug delivery (especially in cancer treatment), smart nanohydrogels in food applications, coatings, and elastomers. The present review summarizes the latest research regarding major IA production pathways, metabolic engineering procedures, and the synthesis and applications of novel polymeric materials.

Electrolytic Conversion of Bicarbonate into CO in a Flow Cell

Electrochemical CO2 reduction offers a method to use renewable electricity to convert CO2 into CO and other carbon-based chemical building blocks. While nearly all studies rely on a CO2 feed, we show herein that aqueous bicarbonate solutions can also be electrochemically converted into CO gas at meaningful rates in a flow cell. We achieved this result in a flow cell containing a bipolar membrane (BPM) and a silver nanoparticle catalyst on a porous carbon support. Electrolysis upon a N2-saturated 3.0-M potassium bicarbonate electrolyte solution yields CO with a faradaic efficiency (F.E.CO) of 81% at 25 mA cm-2 and 37% at 100 mA cm-2. This output is comparable to the analogous experiment where the electrolyte is saturated with gaseous CO2 (faradaic efficiency for CO is 78% at 25 mA cm-2 and 35% at 100 mA cm-2). The H+ flux from the BPM is critical to this chemistry in that it reacts with the bicarbonate feed to generate CO2, which is then reduced to CO at the gas diffusion electrode. These results are important in that they show that the addition of gaseous CO2 to bicarbonate electrolytes is not necessary in order to obtain reduced carbon products with a flow cell architecture. This process offers a means of using electrolysis to bypass the thermally-intensive step of extracting CO2 from bicarbonate solutions generated in carbon capture schemes.

The Gram-Positive Bacterial Cell Wall.

The chapter about the Gram-positive bacterial cell wall gives a brief historical background on the discovery of Gram-positive cell walls and their constituents and microscopic methods applied for studying the Gram-positive cell envelope. Followed by the description of the different chemical building blocks of peptidoglycan and the biosynthesis of the peptidoglycan layers and high turnover of peptidoglycan during bacterial growth. Lipoteichoic acids and wall teichoic acids are highlighted as major components of the cell wall. Characterization of capsules and the formation of extracellular vesicles by Gram-positive bacteria close the section on cell envelopes which have a high impact on bacterial pathogenesis. In addition, the specialized complex and unusual cell wall of mycobacteria is introduced thereafter. Next a short back view is given on the development of electron microscopic examinations for studying bacterial cell walls. Different electron microscopic techniques and methods applied to examine bacterial cell envelopes are discussed in the view that most of the illustrated methods should be available in a well-equipped life sciences orientated electron microscopic laboratory. In addition, newly developed and mostly well-established cryo-methods like high-pressure freezing and freeze-substitution (HPF-FS) and cryo-sections of hydrated vitrified bacteria (CEMOVIS, Cryo-electron microscopy of vitreous sections) are described. At last, modern cryo-methods like cryo-electron tomography (CET) and cryo-FIB-SEM milling (focus ion beam-scanning electron microscopy) are introduced which are available only in specialized institutions, but at present represent the best available methods and techniques to study Gram-positive cell walls under close-to-nature conditions in great detail and at high resolution.

Engineering Clostridium for improved solvent production: recent progress and perspective.

Clostridia are Gram-positive, spore-forming, obligate anaerobic bacteria that can produce solvents such as acetone, ethanol, and butanol, which can be used as biofuels or building block chemicals. Many successful attempts have been made to improve solvent yield and titer from sugars through metabolic engineering of solventogenic and acidogenic clostridia. More recently, cellulolytic and acetogenic clostridia have also attracted high interests for their ability to utilize low-cost renewable substrates such as cellulose and syngas. Process engineering such as in situ butanol recovery and consolidated bioprocessing (CBP) has been developed for improved solvent titer and productivity. This review focuses on metabolic and process engineering strategies for solvent production from sugars, lignocellulosic biomass, and syngas by various clostridia, including conventional solventogenic Clostridium acetobutylicum, engineered acidogens such as C. tyrobutyricum and C. cellulovorans, and carboxydotrophic acetogens such as C. carboxidivorans and C. ljungdahlii.

Species-specific transcriptomic responses in Daphnia magna exposed to a bio-plastic production intermediate

Hydroxymethylfurfural (HMF) is a plant-based chemical building block that could potentially substitute petroleum-based equivalents, yet ecotoxicological data of this compound is currently limited. In this study, the effects of HMF on the reproduction and survival of Daphnia magna were assessed through validated ecotoxicological tests. The mechanism of toxicity was determined by analysis of transcriptomic responses induced by exposure to different concentrations of HMF using RNA sequencing. HMF exerted toxicity to D. magna with an EC50 for effects on reproduction of 17.2 mg/l. HMF exposure affected molecular pathways including sugar and polysaccharide metabolism, lipid metabolism, general stress metabolism and red blood cell metabolism, although most molecular pathways affected by HMF exposure were dose specific. Hemoglobin genes, however, responded in a sensitive and dose-related manner. No induction of genes involved in the xenobiotic metabolism or oxidative stress metabolism pathway could be observed, which contrasted earlier observations on transcriptional responses of the terrestrial model Folsomia candida exposed to the same compound in a similar dose. We found 4189 orthologue genes between D. magna and F. candida, yet only twenty-one genes of those orthologues were co-regulated in both species. The contrasting transcriptional responses to the same compound exposed at a similar dose between D. magna and F. candida indicates limited overlap in stress responses among soil and aquatic invertebrates. The dose-related expression of hemoglobin provides further support for using hemoglobin expression as a biomarker for general stress responses in daphnids.

Directed Evolution of a Cytochrome P450 Carbene Transferase for Selective Functionalization of Cyclic Compounds.

Transfers of carbene moieties to heterocycles or cyclic alkenes to obtain C(sp2)-H alkylation or cyclopropane products are valuable transformations for synthesis of pharmacophores and chemical building blocks. Through their readily tunable active-site geometries, hemoprotein "carbene transferases" could provide an alternative to traditional transition metal catalysts by enabling heterocycle functionalizations with high chemo-, regio-, and stereocontrol. However, carbene transferases accepting heterocyclic substrates are scarce; the few enzymes capable of heterocycle or cyclic internal alkene functionalization described to date are characterized by low turnovers or depend on artificially introduced, costly iridium-porphyrin cofactors. We addressed this challenge by evolving a cytochrome P450 for highly efficient carbene transfer to indoles, pyrroles, and cyclic alkenes. We first developed a spectrophotometric high-throughput screening assay based on 1-methylindole C3-alkylation that enabled rapid analysis of thousands of P450 variants and comprehensive directed evolution via random and targeted mutagenesis. This effort yielded a P450 variant with 11 amino acid substitutions and a large deletion of the non-catalytic P450 reductase domain, which chemoselectively C3-alkylates indoles with up to 470 turnovers per minute and 18 000 total turnovers. We subsequently used this optimized alkylation variant for parallel evolution toward more challenging heterocycle carbene functionalizations, including C2/ C3 regioselective pyrrole alkylation, enantioselective indole alkylation with ethyl 2-diazopropanoate, and cyclic internal alkene cyclopropanation. The resulting set of efficient biocatalysts showcases the tunability of hemoproteins for highly selective functionalization of cyclic targets and the power of directed evolution to enhance the scope of new-to-nature enzyme catalysts.

Gevo announces breakthrough development of renewable isoprene, a key chemical building block for producing rubber and rubber products

A movable shading device installed on an adaptive façade is able to change the positions of the shades according to the various control objectives (i.e. daylighting, thermal comfort, glare, energy, etc.) of the occupant. Since the key variables and the control method may change according to the control objectives, it is important to determine the hourly states of the shades in consideration of all of these factors. This study proposes a multi-purposes control strategy of adaptive facades for heating, cooling, lighting energy and glare. To depict the movements of the movable shading devices, the operable range is represented by an n number of fixed shade states having constant intervals. The control strategy entails deriving allowable shade states for glare prevention and energy conservation independently and then deriving the intersection range between the two shade state ranges. A case study was performed to verify the changes in hourly shade states and the energy performance of the envelope obtained by applying the proposed control strategy to an adaptive façade having a movable folding type shading device. The results of the case study show that hourly shade states were determined to satisfy the objectives of glare prevention and energy conservation simultaneously based on weather conditions and indoor requirement settings. From the case study, it can be seen that the proposed method can block the entry of direct solar radiation by lowering the unshaded fraction according to whether or not there would be discomfort glare while increasing the view factor in certain sections to promote the entry of diffuse solar radiation into the indoor space during the cooling and heating periods. The results of the case study also show that there can be large differences in the heating, cooling, and lighting energy performance of the building envelope for each orientation depending on the order of priority given to the objectives of the shading control, i.e. the objective of energy conservation only and the objective of simultaneous glare prevention and energy conservation. However, it was possible to effectively reduce the differences in energy proportions by adopting translucent shades.

A co-expression system to shift the equilibrium of transamination reactions toward the synthesis of enantiomerically pure amines

The synthesis of chiral amines as important pharmaceutical and fine chemical building blocks can be carried out with amine transaminases. The reaction equilibrium is often unfavorable. There are several methods to shift the equilibrium by co-product removal. One strategy employs isopropylamine as co-substrate resulting in the co-product acetone which can easily be evaporated under reduced pressure. However, many amine transaminases do not accept isopropylamine without further protein engineering. A subtler and generally applicable method uses alanine as co-substrate. A lactate dehydrogenase and a glucose dehydrogenase are added to remove the co-product pyruvate. Drawbacks are high costs for enzyme production and the addition of high amounts of biomass to reaction mixtures.We overcame these drawbacks by co-expression of an amine transaminase with a lactate dehydrogenase and a glucose dehydrogenase in a recombinant Escherichia coli strain. We further demonstrated the applicability on preparative scale. We used the E. coli cell free extract in reactions with up to 74 g/L substrate load achieving yields of >95% in reaction volumes of 10 mL–200 mL.

Metabolic engineering of the type I methanotroph Methylomonas sp. DH-1 for production of succinate from methane

Methane-utilizing methanotrophs are fascinating systems for methane bioconversion. Methylomonas sp. DH-1, a novel type I methanotroph isolated from brewery sludge, has been evaluated as a promising candidate for an industrial bio-catalyst. Succinate has been considered one of the top building block chemicals for the agricultural, food, and pharmaceutical industries. In this study, Methylomonas sp. DH-1 was engineered to accumulate succinate as a desired product. The TCA cycle and enzymes diverting carbon flux to acetate or formate were modified or deleted to improve succinate productivity. By deleting succinate dehydrogenase (sdh) in the TCA cycle, succinate production increased dramatically ∼10 times compared to that of the wild type. In addition, the maximum succinate titer of ∼134 mg/L (DS-GL) was achieved by integrating glyoxylate shunt enzymes from the E. coli MG1655 strain. Pyruvate formate lyase (pfl) and acetate kinase-phosphotransacetylase (ack-pta) genes were disrupted to further concentrate carbon flux to the TCA cycle. However, these additional disruptions of competitive pathways did not affect cell growth or succinate production positively. The mutant strain DS-GL, which showed the best succinate production, was grown in a fed-batch bioreactor, and higher cell growth and succinate production (∼195 mg/L succinate with 0.0789 g-succinate/g-methane yield) were achieved. In this study, we demonstrated a novel platform for microbial conversion of methane to succinate using methanotroph.

Resolving the Ultrafast Changes of Chemically Inequivalent Metal–Ligand Bonds in Photoexcited Molecular Complexes with Transient X-ray Absorption Spectroscopy

Photoactive transition-metal complexes that incorporate heteroleptic ligands present a first coordination shell, which is asymmetric. Although it is generally expected that the metal–ligand bond lengths respond differently to photoexcitation, resolving these fine structural changes remains experimentally challenging, especially for flexible multidentate ligands. In this work, ultrafast X-ray absorption spectroscopy is employed to capture directly the asymmetric elongations of chemically inequivalent metal–ligand bonds in the photoexcited spin-switching FeII complex [FeII(tpen)]2+ solvated in acetonitrile, where tpen denotes N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,2-ethylenediamine. The possibility to correlate precisely the nature of the donor/acceptor coordinating atoms to specific photoinduced structural changes within a binding motif will provide advanced diagnostics for optimizing numerous photoactive chemical and biological building blocks.

Bioinspired Design of Lysolytic Triterpenoid-Peptide Conjugates that Kill African Trypanosomes.

Humans have evolved a natural immunity against Trypanosoma brucei infections, which is executed by two serum (lipo)protein complexes known as trypanolytic factors (TLF). The active TLF ingredient is the primate-specific apolipoprotein L1 (APOL1). The protein has a pore-forming activity that kills parasites by lysosomal and mitochondrial membrane fenestration. Of the many trypanosome subspecies, only two are able to counteract the activity of APOL1; this illustrates its evolutionarily optimized design and trypanocidal potency. Herein, we ask whether a synthetic (syn) TLF can be synthesized by using the design principles of the natural TLF complexes but with different chemical building blocks. We demonstrate the stepwise development of triterpenoid-peptide conjugates, in which the triterpenoids act as a cell-binding, uptake and lysosomal-transport modules and the synthetic peptide GALA acts as a pH-sensitive, pore-forming lysolytic toxin. As designed, the conjugate kills infective-stage African trypanosomes through lysosomal lysis thus demonstrating a proof-of-principle for the bioinspired, forward-design of a synTLF.

Evolution and the single cell: Metabolic diversity in tomato

Research in the Last group focuses on specialized metabolism in glandular trichomes of tomato and other plants in the Solanaceae. Acylsugars – relatively simple metabolites typically composed of sucrose or glucose and C2 to C12 acylesters – are produced in the tip cell of the long hairs of domesticated and wild tomato. Despite being derived from simple chemical building blocks, tremendous variation in acylsugar structures is observed within and across species. Some of the changes in products and enzymatic activities have occurred over remarkably short evolutionary timeframes. The talk will describe our results documenting ‘recruitment’ of enzymes of central metabolism to acylsugar biosynthesis, as well as studies of BAHD acyltransferase evolution. I will emphasize how comparative biochemistry led to insights into how gene duplication, neofunctionalization and gene loss contributed to the impressive acylsugar diversity observed in domesticated and wild tomato species. Work towards understanding the evolutionary history of this metabolic network over tens of millions of years of evolution of the Solanaceae will be described.Support or Funding InformationNSF IOS‐1546617 NIH 1T32GM110523 NSF CBET‐1565232This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Development of microtiter plate scale CRISPR/Cas9 transformation method for Aspergillus niger based on in vitro assembled ribonucleoprotein complexes

BackgroundThe CRISPR/Cas9 is currently the predominant technology to enhance the genome editing efficiency in eukaryotes. Established tools for many fungal species exist while most of them are based on in vivo expressed Cas9 and guide RNA (gRNA). Alternatively, in vitro assembled Cas9 and gRNA ribonucleoprotein complexes can be used in genome editing, however, only a few examples have been reported in fungi. In general, high-throughput compatible transformation workflows for filamentous fungi are immature.ResultsIn this study, a CRISPR/Cas9 facilitated transformation and genome editing method based on in vitro assembled ribonucleoprotein complexes was developed for the filamentous fungus Aspergillus niger. The method was downscaled to be compatible with 96-well microtiter plates. The optimized method resulted in 100% targeting efficiency for a single genomic target. After the optimization, the method was demonstrated to be suitable for multiplexed genome editing with two or three genomic targets in a metabolic engineering application. As a result, an A. niger strain with improved capacity to produce galactarate, a potential chemical building block, was generated.ConclusionsThe developed microtiter plate compatible CRISPR/Cas9 method provides a basis for high-throughput genome editing workflows in A. niger and other related species. In addition, it improves the cost-effectiveness of CRISPR/Cas9 genome editing methods in fungi based on in vitro assembled ribonucleoproteins. The demonstrated metabolic engineering example with multiplexed genome editing highlights the applicability of the method.

Photochemical and photocatalytic degradation of 1-propanol using UV/H2 O2 : Identification of malonate as byproduct.

1-propanol is a primary alcohol extensively used in the pharmaceutical, chemical, and food industries. It has been also found as a contaminant in the atmosphere and is considered a model compound to mimic the behavior and fate of aliphatic alcohols exposed to environmental conditions. In order to understand that role of relevant variables, this paper presents results obtained with a simple experimental set-up to investigate the reactivity of 1-propanol under mild oxidizing conditions. Coupling this system with CE-C4 D allowed the quantification of the carboxylic acids formed. For the described experiments, aqueous solutions of 1-propanol were placed inside a photoreactor and oxidized upon the addition of TiO2 and/or H2 O2 . According to the described results, the addition of H2 O2 (0.1% w/w) was the most significant variable, roughly tripled the amount of carboxylic acids generated and led to the conversion of up to 70% of the initially available 1-propanol (1mmol/L). More importantly, the reaction yielded the formation (within 10 min) of propionate (50µmol/L), acetate (400µmol/L), formate (50µmol/L), and malonate (200µmol/L). The latter is critically important because it represents the first example of the photochemical oxidation of both terminal carbons of the C3 -chain of 1-propanol under mild conditions, and opens new avenues for the production of this important chemical building block.

Enantiomeric Tartaric Acid Production Using cis-Epoxysuccinate Hydrolase: History and Perspectives.

Tartaric acid is an important chiral chemical building block with broad industrial and scientific applications. The enantioselective synthesis of l(+)- and d(−)-tartaric acids has been successfully achieved using bacteria presenting cis-epoxysuccinate hydrolase (CESH) activity, while the catalytic mechanisms of CESHs were not elucidated clearly until very recently. As biocatalysts, CESHs are unique epoxide hydrolases because their substrate is a small, mirror-symmetric, highly hydrophilic molecule, and their products show very high enantiomeric purity with nearly 100% enantiomeric excess. In this paper, we review over forty years of the history, process and mechanism studies of CESHs as well as our perspective on the future research and applications of CESH in enantiomeric tartaric acid production.