Bulk Chemicals Research Articles

Metabolic Engineering of Corynebacterium glutamicum for the Production of the Four-Carbon Platform Chemicals γ-Hydroxybutyrate and γ-Butyrolactone.

γ-Hydroxybutyrate (GHB) is an important C4 platform chemical, serving as a crucial precursor for the synthesis of various bulk chemicals, including γ-butyrolactone (GBL) and 1,4-butanediol (1,4-BDO). In this study, we report the systematic metabolic engineering of Corynebacterium glutamicum for the biological production of GHB from glucose via the introduction of a glutamate-derived pathway. We showed that C. glutamicum is a promising host for producing GHB due to its higher tolerance to GHB as compared to other chassis. By screening key enzymes capable of converting glutamate into GHB and blocking byproduct synthesis pathways, an engineered C. glutamicum strain was developed that achieved a GHB production titer of 30.6 g/L. Comparative transcriptome analysis was subsequently employed to identify previously uncharacterized aldehyde dehydrogenases responsible for succinate accumulation, and knockout of the corresponding genes led to an increased GHB titer of 33.7 g/L. Ultimately, the integration of a phosphoketolase-mediated nonoxidative glycolysis (NOG) pathway further enhanced GHB production, resulting in an accumulation of 38.3 g/L of GHB with a yield of 0.615 mol/mol glucose during batch fermentation. The GHB in the fermentation broth can be efficiently converted into GBL by acid treatment with a yield of 0.970 mol/mol.

New insight into Clostridium butyricum-ferroferric oxide hybrid system in exogenous carbon dioxide-assisted anaerobic fermentation for acetate and butyrate production

Mixotrophic cultivation, utilizing both gas and organic substances, is commonly employed to minimize the carbon loss during anaerobic fermentation of bulk chemicals. Herein, a novel Clostridium butyricum-ferroferric oxide (Fe3O4) hybrid system, enhanced by exogenous carbon dioxide (CO2), was proposed to improve carbon recovery and optimize metabolite production. The results demonstrated that exogenous CO2 improved metabolite selectivity towards acetate/butyrate, while also accelerating CO2 fixation. Compared to pure Clostridium butyricum, the hybrid system significantly increased carbon conversion to primary metabolites, boosting butyrate and acetate production by 18.7 % and 18.4 %, respectively. Enzyme activity assays revealed that Fe3O4 and exogenous CO2 acted synergistically, enhancing the activities of key enzymes involved in CO2 assimilation. Additionally, Fe3O4 facilitated intra- and extracellular electron transfer, further improving the fermentation process. This study offers new insights into the combined effects of exogenous CO2 and Fe3O4 on anaerobic fermentation, providing an efficient strategy for carbon recovery and selective acetate/butyrate production.

Genetic optimization of the human gut bacterium Phocaeicola vulgatus for enhanced succinate production

The demand for sustainably produced bulk chemicals is constantly rising. Succinate serves as a fundamental component in various food, chemical, and pharmaceutical products. Succinate can be produced from sustainable raw materials using microbial fermentation and enzyme-based technologies. Bacteroides and Phocaeicola species, widely distributed and prevalent gut commensals, possess enzyme sets for the metabolization of complex plant polysaccharides and synthesize succinate as a fermentative end product. This study employed novel molecular techniques to enhance succinate yields in the natural succinate producer Phocaeicola vulgatus by directing the metabolic carbon flow toward succinate formation. The deletion of the gene encoding the methylmalonyl-CoA mutase (Δmcm, bvu_0309-0310) resulted in a 95% increase in succinate production, as metabolization to propionate was effectively blocked. Furthermore, deletion of genes encoding the lactate dehydrogenase (Δldh, bvu_2499) and the pyruvate:formate lyase (Δpfl, bvu_2880) eliminated the formation of fermentative end products lactate and formate. By overproducing the transketolase (TKT, BVU_2318) in the triple deletion mutant, succinate production increased from 3.9 mmol/g dry weight in the wild type to 10.9 mmol/g dry weight. Overall, succinate yield increased by 180% in the new mutant strain P. vulgatus Δmcm Δldh Δpfl pG106_tkt relative to the parent strain. This approach is a proof of concept, verifying the genetic accessibility of P. vulgatus, and forms the basis for targeted genetic optimization. The increase of efficiency highlights the huge potential of P. vulgatus as a succinate producer with applications in sustainable bioproduction processes.Key points• Deleting methylmalonyl-CoA mutase gene in P. vulgatus doubled succinate production• Triple deletion mutant with transketolase overexpression increased succinate yield by 180%• P. vulgatus shows high potential for sustainable bulk chemical production via genetic optimization

(Invited) Fundamentals of Single Atom Alloy Catalysts for Electrochemical Nitrate Reduction to Ammonia

Electrochemical conversion of toxic nitrate into useful ammonia provides a route to remediating the most frequent water pollutant while simultaneously generating one of the most produced bulk chemicals. While highly desirable, this conversion is plagued by complications including a highly branching reaction pathway - which can produce highly toxic undesirable products, the need to reduce a negatively charged species, a relatively low nitrate concentration, and competition for electrons between nitrate reduction and parasitic hydrogen evolution. Therefore, electrocatalysts must be developed which are highly selective not only for nitrate over other species in the water matrix, but also selective to the desired ammonia product. Single atom alloy catalysts, where a single atom of one element is embedded in a solvating phase of a secondary element, provides an opportunity to engineer catalysts with atomic level precision. In this presentation, we will outline the fundamental behavior of single atom alloy for nitrate reduction. We explore this topic through density functional theory calculations of the reaction mechanisms, including thermodynamics and kinetic aspects. Particularly, we will discuss the effect of single atom identity, effect of matrix element, and pH and potential. We show that the ability of the single atom to localize the N* species drives the reduction towards ammonia formation, as exemplified by Ru in Cu, while facile exchange of N* between the single atom site and the matrix leads to the formation of N2 or other undesirable products, as exemplified by Pd in Cu and Au in Cu, respectively. We also discuss the importance of the selection of the solvating element; for example, Cu is a good solvating metal because it is a good conductor, while minimizing the hydrogen evolution reaction. Further, we discuss the limits of pH and potential on the performance. In general, higher pH and more moderately negative potentials favor nitrate reduction to NH3 or N2, while lower pH and more negative potentials drive H2 evolution, and generation of NOx species.

Highly active iron oxide@NC catalyst derived from the iron acetate/polyacrylonitrile threads: Driving nitroarene conversion to value‐added amines

AbstractChemoselective reduction of nitroarenes to corresponding arylamines is a significant reaction in the chemical industry. However, in the presence of other reducible groups, including halogenated nitrobenzene, nitrobiphenyl, and nitroquinoline in the same molecule of nitroaromatics, the control of chemoselectivity remains challenging. Here, a facile fabrication of a heterogeneous iron‐based catalyst is reported as a potential alternative to precious metal catalysts for the chemoselective reduction of nitroarenes. The pyrolysis of iron acetate/polyacrylonitrile (PAN) template under an inert atmosphere furnishes active Fe3O4 nanoparticles (NPs) encapsulated in nitrogen‐doped (N‐doped) carbon layers, which can provide more catalytic active sites (Fe3O4/PAN@800). Notably, non‐precious iron oxide NPs supported on N‐doped carbon support prevent aggregation, thereby enhancing the catalytic activity. The sustainable and reusable Fe3O4/PAN@800 catalyst, having only 0.8% metal content as demonstrated by x‐ray photoelectron spectroscopy, delivers excellent yields of corresponding amines from differently functionalized nitroarenes. Hydrogenation of a series of structurally functionalized nitroarenes produced excellent yields of anilines, which serve as building blocks and intermediates for fine and bulk chemicals. Hydrogenation of 2‐chloro‐3‐nitropyridine, 2‐nitro‐1,1′‐biphenyl, ortho‐nitroaniline, and 4‐aminophenyl acrylonitrile yielded respective anilines up to 99%. The active sites of Fe3O4 have magnetic performance, hence, the catalyst can be easily recovered using a magnet and reused for at least five cycles without significant loss of catalytic activity. Therefore, the easily prepared, cost‐effective, and reusable Fe3O4/PAN@800 catalyst presented in this study shows potential for applications in the selective reduction of aromatic nitro compounds. Consequently, this study potentially establishes a guideline for the facile preparation of abundant transition‐non‐noble metal‐based reusable supported catalysts for various applications in the chemical industry.

Modularization of Immobilized Multienzyme Cascades for Continuous-Flow Enantioselective C-H Amination.

Multienzyme cascades (MECs) have gained much attention in synthetic chemistry but remain far from being a reliable synthetic tool. Here we report a four-enzyme cascade comprising a cofactor-independent and a cofactor self-sustaining bienzymatic modules for the enantioselective benzylic C-H amination of arylalkanes, a challenging transformation from bulk chemicals to high value-added chiral amines. The two modules were subsequently optimized by enzyme co-immobilization with microenvironmental tuning, and finally integrated in a gas-liquid segmented flow system, resulting in simultaneous improvements in enzyme performance, mass transfer, system compatibility, and productivity. The flow system enabled continuous C-H amination of arylalkanes (up to 100 mM) utilizing the sole cofactor NADH (0.5 mM) in >90 % conversion, achieving a high space-time yield (STY) of 3.6 g ⋅ L-1 ⋅ h-1, which is a 90-fold increase over the highest value previously reported.

Modularization of Immobilized Multienzyme Cascades for Continuous‐Flow Enantioselective C−H Amination

AbstractMultienzyme cascades (MECs) have gained much attention in synthetic chemistry but remain far from being a reliable synthetic tool. Here we report a four‐enzyme cascade comprising a cofactor‐independent and a cofactor self‐sustaining bienzymatic modules for the enantioselective benzylic C−H amination of arylalkanes, a challenging transformation from bulk chemicals to high value‐added chiral amines. The two modules were subsequently optimized by enzyme co‐immobilization with microenvironmental tuning, and finally integrated in a gas‐liquid segmented flow system, resulting in simultaneous improvements in enzyme performance, mass transfer, system compatibility, and productivity. The flow system enabled continuous C−H amination of arylalkanes (up to 100 mM) utilizing the sole cofactor NADH (0.5 mM) in >90 % conversion, achieving a high space‐time yield (STY) of 3.6 g ⋅ L−1 ⋅ h−1, which is a 90‐fold increase over the highest value previously reported.

Electrocatalytic Glycerol Upgrading into Glyceric Acid on Ni3Sn Intermetallic Compound.

Electrochemical glycerol oxidation features an attractive approach of converting bulk chemicals into high-value products such as glyceric acid. Nonetheless, to date, the major product selectivity has mostly been limited as low-value C1 products such as formate, CO, and CO2, due to the fast cleavage of carbon-carbon (C-C) bonds during electro-oxidation. Herein, the study develops an atomically ordered Ni3Sn intermetallic compound catalyst, in which Sn atoms with low carbon-binding and high oxygen-binding capability allow to tune the adsorption of glycerol oxidation intermediates from multi-valent carbon binding to mono-valent carbon binding, as well as enhance *OH binding and subsequent nucleophilic attack. The Ni3Sn electrocatalyst exhibits one of the highest glycerol-to-glyceric acid performances, including a high glycerol conversion rate (1199µmol h-1) and glyceric acid selectivity (62 ± 3%), a long electrochemical stability of > 150 h, and the capability of direct conversion of crude glycerol (85% purity) into glyceric acid. The work features the rational design of highly ordered catalytic sites for tailoring intermediate binding and reaction pathways, thereby facilitating the efficient production of high-value chemical products.

Metal–carbene-guided twofold cross-coupling of ethers with chromium catalysis

Coupling by metal–carbene transfer enables the formation of several different bonds at the carbenoid site, enabling prochiral Csp3 centers that are fundamental three-dimensional substructures for medicines to be forged with increased efficiency. However, strategies using bulk chemicals are rare because of the challenge of breaking two unactivated geminal bonds. Herein, we report the reactivity of ethers to form metal–carbene intermediate by cleavage of α-Csp3–H/Csp3–O bonds, which achieve selective coupling with arylmagnesium bromides and chlorosilanes. These couplings are catalysed by cyclic (alkyl)(amino)carbene-chromium complex and enable the one-step formation of 1,n-arylsilyl alcohols and α-arylated silanes. Mechanistic studies indicate that the in-situ formed low-valent Cr might react with iodobenzene to form phenyl radical species, which abstracts the α-H atom of ether in giving α-oxy radical. The latter combines with Cr by breaking α-Csp3–O bond to afford metal–carbene intermediate, which couples with aryl Grignard and chlorosilane to form two σ-bonds.

Co2(CO)8 as a CO-source for Pd-catalyzed Carbonylations: An Update

Abstract: Palladium-catalyzed carbonylative cross-coupling reactions with various carbon monoxide (CO) sources cultivate competent routes for the synthesis of bulk and value-added chemicals. However, the practical use of this odorless, inflammable, lethal gas has always raised a concern for chemists. The attention and advancement of various CO-surrogates is surely wel-comed as a green alternative to CO-gas. However, the main concern lies in the suitability and scalability of these CO-surrogate-driven reactions. Literature showed the progress of various ways to make in-situ CO from these CO surrogates. One of the most convenient sources is using metal carbonyls which are already known to lose CO easily. Among all the kinds, Mo(CO)6 gained much popularity but its toxic nature and demand for high temperatures restricted its use. However, Co2(CO)8 is popular as a catalyst but as an in-situ CO-source reports are scarce. This low-melting CO-releaser was found effective in flourishing aminocarbonylation, alkoxycar-bonylation, and reductive carbonylation under mild conditions. This mini-review portrays the recent developments of palladium-catalyzed carbonylation reactions using Co2(CO)8 as a CO source.

Diols production from pyrolysis oil water‐soluble fraction

AbstractBACKGROUNDThe production of value‐added chemicals from pyrolysis oil or its fractions is of great significance for the valorization of biomass. Diols, including ethylene glycol (EG) and 1,2‐propylene glycol (1,2‐PG), are important bulk chemicals with widespread industrial applications. Here we investigated the production of diols from pyrolysis oil water‐soluble fraction (WS) using a hybrid catalyst (Ni + H2WO4).RESULTSFirstly, levoglucosan, glycolaldehyde and acetol, three main components in WS, were respectively selected as the single model compound, and their respective conversions into diols were investigated at different temperatures for different reaction times. The result showed the optimum reaction temperature and time were 180 °C and 2 h respectively, under which a EG yield of 53.8% and 1,2‐PG yield of 5.2% were obtained from levoglucosan conversion, a EG yield of 98.6% was obtained from glycolaldehyde conversion, and a 1,2‐PG yield of 98.5% was obtained from acetol conversion. The reaction pathway of levoglucosan conversion was analyzed. Secondly, the model mixture of levoglucosan, glycolaldehyde and acetol was used to simulate the real WS, and their conversion was investigated at different ratios of H2WO4 to Ni. The result showed the optimum catalyst composition was 0.15 g H2WO4 and 0.3 g Ni, under which a EG yield of 76.4% and 1,2‐PG yield of 38.4% were obtained. Thirdly, the real original WS was converted under the optimum reaction conditions and the result only gave a EG yield of 19.1% and 1,2‐PG yield of 25.8% (based on the carbon moles of main substrates), which were much less than the two yields of model mixture. That was related to the presences of other types of chemicals in original WS. After the original WS being adsorbed by activated carbon, the yields of EG and 1,2‐PG could be increased to 39.2% and 37.9%, respectively.CONCLUSIONThe presences of certain other types of chemicals (such as acids, furans, phenolics and cyclopentanones) in original WS inhibited the production of diols. The activated carbon adsorption could efficiently remove most of furans, phenolics and cyclopentanones in original WS and increased significantly the diols yields. © 2024 Society of Chemical Industry (SCI).

Utilization of orange peel waste for sustainable amino acid production by Corynebacterium glutamicum.

Oranges are the most processed fruit in the world-it is therefore apparent that the industrial production of orange juice generates large quantities of orange peel as a by-product. Unfortunately, the management of the orange peel waste leads to economic and environmental problems. Meanwhile, the use of sustainable raw materials for the production of bulk chemicals, such as amino acids, is becoming increasingly attractive. To address both issues, this study focused on the use of orange peel waste as a raw material for media preparation for the production of amino acids by engineered Corynebacterium glutamicum. C. glutamicum grew on pure orange peel hydrolysate (OPH) and growth was enhanced by the addition of a nitrogen source and a pH buffer. Inhibitory effects by the combination of high concentrations of OPH, (NH4)2SO4, and MOPS buffer in the wild-type strain (WT), were overcome in the tyrosine-producing engineered C. glutamicum strain AROM3. Genetic modifications that we identified to allow for improved growth rates under these conditions included the deletions of the vanillin dehydrogenase gene vdh, the ʟ-lactate dehydrogenase gene ldhA and the 19 genes comprising cluster cg2663-cg2686. A growth inhibiting compound present in high concentrations in the OPH is 5-(hydroxymethyl)furfural (HMF). We identified vdh as being primarily responsible for the oxidation of HMF to its acid 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), as the formation of HMFCA was reduced by 97% upon deletion of vdh in C. glutamicum WT. In addition, we showed that growth limitations could be overcome by adjusting the media preparation, using a combination of cheap ammonia water and KOH for pH neutralization after acidic hydrolysis. Overall, we developed a sustainable medium based on orange peel waste for the cultivation of C. glutamicum and demonstrated the successful production of the exemplary amino acids ʟ-arginine, ʟ-lysine, ʟ-serine, ʟ-valine and ʟ-tyrosine.

O/S Exchange Reaction in Synthesizing Sulfur-Containing Polymers.

Using carbon disulfide (CS2) and carbonyl sulfide (COS) as sulfur-containing and one-carbon feedstocks to make value-added products is paramount for both pure and applied chemistry and environmental science. One of the practical strategies is to copolymerize these bulk chemicals with epoxides to produce sulfur-containing polymers. This approach contributes to improving the sustainability of polymer manufacturing, provides highly desired functional polymer materials, and has attracted much attention. However, these copolymerizations invariably exhibit the intensely complicated chemistry of O/S exchange reaction, leading to sulfur-containing polymers with diverse architectures. As the understanding of O/S exchange continues to deepen, recent efforts have guided significant advances in the synthesis of CS2- and COS-based polymers. This review examines the O/S exchange chemistry and summarizes the recent progress in this field to promote the further advance of synthesizing sulfur-containing polymers from CS2 and COS.

An Extremely Sensitive Ultra-High Throughput Growth Selection Assay for the Identification of Amidase Activity

In the last decades, biocatalysis has offered new perspectives for the synthesis of (chiral) amines, which are essential building blocks for pharmaceuticals, fine and bulk chemicals. In this regard, amidases have been employed due to their broad substrate scope and their independence from expensive cofactors. To expand the repertoire of amidases, tools for their rapid identification and characterization are greatly demanded. In this work an ultra-high throughput growth selection assay based on the production of the folate precursor p-aminobenzoic acid (PABA) is introduced to identify amidase activity. PABA-derived amides structurally mimic the broad class of commonly used chromogenic substrates derived from p-nitroaniline. This suggests that the assay should be broadly applicable for the identification of amidases. Unlike conventional growth selection assays that rely on substrates as nitrogen or carbon source, our approach requires PABA in sub-nanomolar concentrations, making it exceptionally sensitive and ideal for engineering campaigns that aim at enhancing amidase activities from minimally active starting points, for example. The presented assay offers flexibility in the adjustment of sensitivity to suit project-specific needs using different expression systems and fine-tuning with the antimetabolite sulfathiazole. Application of this PABA-based assay facilitates the screening of millions of enzyme variants on a single agar plate within two days, without the need for laborious sample preparation or expensive instruments, with transformation efficiency being the only limiting factor.Key points• Ultra-high throughput assay (tens of millions on one agar plate) for amidase screening• High sensitivity by coupling selection to folate instead of carbon or nitrogen source• Highly adjustable in terms of sensitivity and expression of the engineering target

Diversity and saline-alkali resistance of Coleoptera endosymbiont bacteria in arid and semi-arid climate.

Coleoptera insects, as the first largest order of insect class, have the characteristics of a wide variety and wide distribution. The arid and semi-arid climate makes it more adaptable. By studying the endosymbiont bacteria of Coleoptera insects, we can systematically understand the adaptability of endosymbiont bacteria to host and special environment. Through the analysis of endosymbiont bacteria of Coleoptera insects in different saline-alkali areas in arid and semi-arid regions of Xinjiang, it was found that bacteria in different host samples were resistant to saline-alkali stress. These results suggest that bacteria and their hosts co-evolved in response to this climate. Therefore, this study is of great significance for understanding the endosymbiont bacteria of Coleoptera insects and obtaining extremophile resources (Saline-alkali-resistant chassis strains with modification potential for the production of bulk chemicals and highly robust industrial enzymes).

Structural Characterization of Enzymatic Interactions with Functional Nicotinamide Cofactor Biomimetics

Synthetic nicotinamide biomimetics (NCBs) have emerged as alternatives to the use of natural cofactors. The relatively low cost and ease of manufacture of NCBs may enable the scaling of biocatalytic reactions to produce bulk chemicals (e.g., biofuels and plastics). NCBs are also recognized by only a subset of NAD(P)/NAD(P)H-dependent enzymes, which potentially allows access to orthogonal redox cascades that can be run simultaneously within a single reactor. In the work presented here, a series of NCBs was prepared and tested for activity with alcohol dehydrogenases and ene-reductases. While the NCBs did not support enzymatic activity with the alcohol dehydrogenases, the observed rate of the ene-reductases with NCBs was greater than when incubated with the natural cofactor (consistent with previous observations). We obtained the structures of an ene-reductase and an alcohol dehydrogenase with an NCB bound in their active sites. While the NCB bound to the ene-reductases in a productive position and orientation for hydride transfer to the isoalloxazine ring of the flavin cofactor, the NCB failed to adopt a catalytically competent binding mode in the alcohol dehydrogenase.

Direct site-selective C(sp<sup>3</sup>)–H functionalization of unprotected non-activated alcohols

Free alcohols are ubiquitous in nature, drugs, bulk chemicals, and various complex molecules. The abundantly available free aliphatic alcohols, being inexpensive, are sustainable starting materials in organic synthesis to construct value-added scaffolds. Direct C(sp<sup>3</sup>)–H functionalization of inert bonds in aliphatic alcoholic chain is challenging due to their inactive nature towards chemical reactions and also multiple similar C–H bonds are available for functionalization reaction at a time. Barton process, which is a classical method for generating alkoxyl radicals, has been widely used for the remote functionalization of alcoholic chain using the strategy of 1,5-hydrogen atom transfer (1,5-HAT). However, the requirement for the pre-activation of alcohols not only adds extra and tedious steps but also, these precursors are challenging to prepare and handle. Generating desired alkoxyl radicals from these precursors is a difficult task and also affects the atom economy of reactions. Numerous methods covering the C(sp<sup>3</sup>)–H functionalization of unprotected non-activated alcohols at diverse (α-, β-, γ-, δ-) positions to access functionalized alcohols are elaborated here. A precise and focused compilation will help to understand what has been established and how new methodologies can be developed for the future needs. <br> The bibliography includes 158 references.

A Novel GE-Mackinsey Market Approach: Investment Opportunity for the Biopolymer Packaging Materials

Sustainable development in agriculture seeks to implement a robust bioeconomy strategy by valorizing agricultural resources into value-added products. Compared to primary biomass use, using agriculture residues and wastes can achieve higher reductions in GHG emissions and lower feedstock costs. Bioeconomy has substantial potential for high-value products such as biopolymers, pharmaceuticals, and food and feed additives. Low-value applications like bioenergy, biofuels, and bulk chemicals have a weak potential for bioeconomy development. However, high value-added products, including biopolymers, require an equal focus as other products in the bioeconomy value pyramid that can lift the market to elevate sustainable bioeconomy development. A successful transition through radical innovations must be justifiable, with economic, environmental, and social benefits primarily promoted by stakeholders, businesses, or government organizations. One of the core options would be to know the market potential of the biopolymer products. Here, a methodology for decision-making to evaluate four existing biopolymer packaging materials (Cellulose, PHA, PLA, and starch) in the EU market has been developed using the GE-McKinsey Nine-Box Matrix, considering market attractiveness and product competitive advantage. Market innovations can be fostered by integrating the resource availability and technology advancement indicators to the methodology steps. The methodology considers sustainability advantages for the agriculture sector and promotes the strategic commercialization of biopolymer packaging materials. Product-specific indicators are used to evaluate the market attractiveness and product competitive advantage. The research findings show that PLA biopolymer packaging material has the highest potential for commercialization. The application of this methodology and its results provide a justifiable way of determining the investments in value-added products and allow investors to make the right decision-making choice for bioplastic packaging materials, ensuring their sustainability and profitability in the market.

Rapidly engineering an osmotic-pressure-tolerant gut bacterium for efficient non-sterile production of bulk chemicals

The concept of next-generation industrial biotechnology (NGIB) has been presented as a green biomanufacturing approach based on the use of low-cost substrates in an open and continuous non-sterilization fermentation process. However, the realization of NGIB, partially through the utilization of extremophiles, has been impeded by the challenges in engineering these extremophiles. A previously unexplored solution for advancing NGIB is to obtain readily engineerable microorganisms with osmotic-pressure tolerance. Here, Jejubacter sp. L23 strain, a Gram-negative, rod-shaped, osmotic-pressure-tolerant bacterium, was isolated from the gut of superworm Zophobas atratus and identified as a new member of the family Enterobacteriaceae, with high 16S rDNA similarity to Escherichia coli (95.2 %). The growth of L23 strain was observed at 10 to 45 °C and pH 4.0 to 10.0 in the presence of 0 to 12 % (w/v) NaCl. We systematically investigated the genetic parts, molecular tools, and manipulation approaches applicable to the L23 strain, and successfully conducted chromosomal genetic engineering, e.g. base-editing and deletion, by using high-efficiency CRISPR systems under low-salt conditions. Furthermore, the metabolic network of L23 strain was rewired to obtain the engineered L23R7 strain, which could display stable expression of exogenous genes and produce bulk chemicals at high yields using inulin, abundant non-food biomass, and salt water without sterilization. For example, 41 g/L isobutanol was produced by utilizing inulin in a 3-L bioreactor through a non-sterile fermentation process. This potent industrial strain holds the promise of promoting the development of NGIB as a sustainable biomanufacturing solution.

Deposition of Pd, Pt, and PdPt Nanoparticles on TiO2 Powder Using Supercritical Fluid Reactive Deposition: Application in the Direct Synthesis of H2O2.

In this study, we investigated the catalytic properties of mono- and bimetallic palladium (Pd) and platinum (Pt) nanoparticles deposited via supercritical fluid reactive deposition (SFRD) on titanium dioxide (TiO2) powder. Transmission electron microscopy analyses verified that SFRD experiments performed at 353 K and 15.6 MPa enabled the deposition of uniform mono- and bimetallic nanoparticles smaller than 3 nm on TiO2. Electron-dispersive X-ray spectroscopy demonstrated the formation of alloy-type structures for the bimetallic PdPt nanoparticles. H2O2 is an excellent oxidizing reagent for the production of fine and bulk chemicals. However, until today, the design and preparation of catalysts with high H2O2 selectivity and productivity remain a great challenge. The focus of this study was on answering the questions of (a) whether the catalysts produced are suitable for the direct synthesis of hydrogen peroxide (H2O2) in the liquid phase and (b) how the metal type affects the catalytic properties. It was found that the metal type (Pd or Pt) influenced the catalytic performance strongly; the mean productivity of the mono- and bimetallic catalysts decreased in the following order: Pd > PdPt > Pt. Furthermore, all catalysts prepared by SFRD showed a significantly higher mean productivity compared to the catalyst prepared by incipient wetness impregnation.