scholarly journals Efficient Oxidation of Methyl Glycolate to Methyl Glyoxylate Using a Fusion Enzyme of Glycolate Oxidase, Catalase and Hemoglobin

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 943
Author(s):  
Xiangxian Ying ◽  
Can Wang ◽  
Shuai Shao ◽  
Qizhou Wang ◽  
Xueting Zhou ◽  
...  
Keyword(s):  
Value Added ◽  
Crude Enzyme ◽  
Saturation Mutagenesis ◽  
Enzymatic Oxidation ◽  
Glycolate Oxidase ◽  
Reaction Yield ◽  
Side Reactions ◽  
Preparative Scale ◽  
Fusion Enzyme ◽  
Methyl Glycolate

Possessing aldehyde and carboxyl groups, glyoxylic acid and its ester derivatives serve as platform chemicals for the synthesis of vanillin, (R)-pantolactone, antibiotics or agrochemicals. Methyl glycolate is one of the by-products in the coal-to-glycol industry, and we attempted its value-added use through enzymatic oxidation of methyl glycolate to methyl glyoxylate. The cascade catalysis of glycolate oxidase from Spinacia oleracea (SoGOX), catalase from Helicobacter pylori (HpCAT) and hemoglobin from Vitreoscilla stercoraria (VsHGB) was firstly constructed, despite poor catalytic performance. To enable efficient oxidation of methyl glycolate, eight fusion enzymes of SoGOX, HpCAT and VsHGB were constructed by varying the orientation and the linker length. The fusion enzyme VsHGB-GSG-SoGOX-GGGGS-HpCAT was proved to be best, which reaction yield was 2.9 times higher than that of separated enzymes. The enzyme SoGOX was further subjected to directed evolution and site-saturation mutagenesis. The reaction yield of the resulting variant M267T/S362G was 1.9 times higher than that of the wild type. Then, the double substitution M267T/S362G was integrated with fusion expression to give the fusion enzyme VsHGB-GSG-SoGOXmut-GGGGS-HpCAT, which crude enzyme was used as biocatalyst. The use of crude enzyme virtually eliminated side reactions and simplified the preparation of biocatalysts. Under the optimized conditions, the crude enzyme VsHGB-GSG-SoGOXmut-GGGGS-HpCAT catalyzed the oxidation of 200 mM methyl glycolate for 6 h, giving a yield of 95.3%. The development of efficient fusion enzyme and the use of its crude enzyme paved the way for preparative scale application on enzymatic oxidation of methyl glycolate to methyl glyoxylate.

scholarly journals CO2 Metallothermal Reduction to Graphene: The Influence of Zn

2021 ◽  
Vol 3 ◽  
Author(s):  
Carolina Luchetta ◽  
Erica C. Oliveira Munsignatti ◽  
Heloise O. Pastore
Keyword(s):  
Climate Change ◽  
Greenhouse Gas ◽  
Value Added ◽  
Reducing Agent ◽  
Reaction Yield ◽  
3D Graphene ◽  
A Value ◽  
To Come

CO2 is the most important greenhouse gas involved in climate change; it has been a concern for many years and will remain as such in the years to come. CO2 adsorption and CO2 utilization have been studied as methods to mitigate the concentration of the gas in the atmosphere by sequestering and transforming it into a value-added product, capable of being commercialized. With those aims in mind, CO2 reduction into 3D graphene was studied using a Zn–Mg mixture. The results show that Mg is the only reducing agent, and Zn acted as a porogen during graphene formation as the energy released by the reaction between CO2 and Mg is enough to evaporate Zn. Thus, Zn vapor increases graphene porosity and increases the contact of CO2 with Mg, yielding larger masses of graphene. A relationship between the Zn–Mg ratio and the reaction yield was found.

scholarly journals From Cell-Free Protein Synthesis to Whole-Cell Biotransformation: Screening and Identification of Novel α‑Ketoglutarate-Dependent Dioxygenases for Preparative-Scale Synthesis of Hydroxy-l-Lysine

Catalysts ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1038
Author(s):  
Jascha Rolf ◽  
Philipp Nerke ◽  
Annette Britner ◽  
Sebastian Krick ◽  
Stephan Lütz ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Specific Activity ◽  
Value Added ◽  
Small Scale ◽  
Preparative Synthesis ◽  
Preparative Scale ◽  
Whole Cell ◽  
Free Protein ◽  
Starting Point ◽  
Cell Free Protein Synthesis

The selective hydroxylation of non-activated C-H bonds is still a challenging reaction in chemistry. Non-heme Fe2+/α-ketoglutarate-dependent dioxygenases are remarkable biocatalysts for the activation of C-H-bonds, catalyzing mainly hydroxylations. The discovery of new Fe2+/α-ketoglutarate-dependent dioxygenases with suitable reactivity for biotechnological applications is therefore highly relevant to expand the limited range of enzymes described so far. In this study, we performed a protein BLAST to identify homologous enzymes to already described lysine dioxygenases (KDOs). Six novel and yet uncharacterized proteins were selected and synthesized by cell-free protein synthesis (CFPS). The subsequent in vitro screening of the selected homologs revealed activity towards the hydroxylation of l-lysine (Lys) into hydroxy-l-lysine (Hyl), which is a versatile chiral building block. With respect to biotechnological application, Escherichia coli whole-cell biocatalysts were developed and characterized in small-scale biotransformations. As the whole-cell biocatalyst expressing the gene coding for the KDO from Photorhabdus luminescens showed the highest specific activity of 8.6 ± 0.6 U gCDW−1, it was selected for the preparative synthesis of Hyl. Multi-gram scale product concentrations were achieved providing a good starting point for further bioprocess development for Hyl production. A systematic approach was established to screen and identify novel Fe2+/α-ketoglutarate-dependent dioxygenases, covering the entire pathway from gene to product, which contributes to accelerating the development of bioprocesses for the production of value-added chemicals.

scholarly journals Biosynthesis of Chiral Amino Alcohols via an Engineered Amine Dehydrogenase in E. coli

2022 ◽  
Vol 9 ◽  
Author(s):  
Feifei Tong ◽  
Zongmin Qin ◽  
Hongyue Wang ◽  
Yingying Jiang ◽  
Junkuan Li ◽  
...  
Keyword(s):  
Reductive Amination ◽  
Asymmetric Reduction ◽  
Amino Alcohols ◽  
Saturation Mutagenesis ◽  
Preparative Scale ◽  
One Step ◽  
Amine Dehydrogenase ◽  
The One ◽  
Total Turnover ◽  
Chiral Amino Alcohols

Chiral amino alcohols are prevalent synthons in pharmaceuticals and synthetic bioactive compounds. The efficient synthesis of chiral amino alcohols using ammonia as the sole amino donor under mild conditions is highly desired and challenging in organic chemistry and biotechnology. Our previous work explored a panel of engineered amine dehydrogenases (AmDHs) derived from amino acid dehydrogenase (AADH), enabling the one-step synthesis of chiral amino alcohols via the asymmetric reductive amination of α-hydroxy ketones. Although the AmDH-directed asymmetric reduction is in a high stereoselective manner, the activity is yet fully excavated. Herein, an engineered AmDH derived from a leucine dehydrogenase from Sporosarcina psychrophila (SpAmDH) was recruited as the starting enzyme, and the combinatorial active-site saturation test/iterative saturation mutagenesis (CAST/ISM) strategy was applied to improve the activity. After three rounds of mutagenesis in an iterative fashion, the best variant wh84 was obtained and proved to be effective in the asymmetric reductive amination of 1-hydroxy-2-butanone with 4-fold improvements in kcat/Km and total turnover number (TTN) values compared to those of the starting enzyme, while maintaining high enantioselectivity (ee >99%) and thermostability (T5015 >53°C). In preparative-scale reaction, the conversion of 100 and 200 mM 1-hydroxy-2-butanone catalyzed by wh84 was up to 91–99%. Insights into the source of an enhanced activity were gained by the computational analysis. Our work expands the catalytic repertoire and toolbox of AmDHs.

scholarly journals SELECTIVE FORMATION OF LINEAR ALPHA-OLEFINS VIA MICROWAVE CATALYTIC CRACKING OF LIQUID STRAIGHT-CHAIN ALKANES

2019 ◽  
Author(s):  
Vasiliy Alexandrovich Bolotov ◽  
Serguei Fedorovich Tikhov ◽  
Konstantin Radikovich Valeev ◽  
Vladimir Timurovich Shamirzaev ◽  
Valentin Nikolaevich Parmon
Keyword(s):  
Catalytic Cracking ◽  
Porous Ceramic ◽  
Carbon Number ◽  
Value Added ◽  
Thermal Cracking ◽  
Rapid Quenching ◽  
Side Reactions ◽  
Linear Alkylbenzene ◽  
Wide Range ◽  
Alpha Olefins

Linear even-carbon-number alpha-olefins (LAO) with four or more carbon atoms are important compounds of high demand in chemical industry as precursors of a wide range of value-added chemicals [1]. LAO are used as co-monomers for polyethylene production, for the production of alcohols (mainly in detergents and plasticizers) and for synthesis of polyalphaolefins (used in synthetic lubricants). Alpha-olefins (C4, C6, C8 and C10) are mainly used to produce poly(vinyl chloride) plasticizers, high-density and linear low-density polyethylene to impart the stress-crack resistance. C10–C14 alpha-olefins can be used to synthesize linear alkylbenzene sulfonates (synthetic detergents). A conventional route to produce alpha-olefins is oligomerization of ethylene. The process provides production of high quality alpha-olefins but is very costly. If not oligomerization, LAO can be produced by thermal cracking of waxy paraffins but the product is not pure and contains numerous internal olefins, dienes and paraffin impurities. The process is conducted in the vapor phase at relatively low cracking temperatures and needs rapid quenching to prevent side reactions such as isomerization or cyclization. In our previous work [2], we showed that the selectivity to alpha-olefins can be increased considerably via catalytic cracking of n-alkanes under selective MW heating of catalysts. In the present work, the general regularities of MW cracking of n-alkanes are presented. Porous ceramic matrix Al2O3/Al composites (ceramometals) and various carbon materials (CM) having high dielectric losses were studied as supports of the catalysts. MW cracking was conducted with n-C16H34 and n-C28H58. The influence particle size and surface morphology of ceramometals and CM on the structural and group composition of the products was studied. It was established that LAO (C2-C23) and n-alkanes (C2-C26) were the main cracking products under selective MW heating of the used supports. The quantitative analysis of the products demonstrated that the liquid-phase process is more selective to alpha-olefins at the MW catalytic cracking than at the convectional thermal cracking. Silica modification of the surface of CM was shown to suppress spark discharge (usually observed at MW heating of CM); hence, the thermal cleavage of C-C bonds on the CM surface but not in the plasma discharge contributes the most to the formation of radicals. It was shown that the selectivity to liquid alpha-olefin could be more than 85 % under MW heating of cermets in region of the E - field node and decrease considerably in the region of H - field node.

scholarly journals One-pot Synthesis of (R)- and (S)-phenylglycinol From Bio-based L-phenylalanine by an Artificial Biocatalytic Cascade

2021 ◽  
Author(s):  
Jiandong Zhang ◽  
Ning Qi ◽  
Lili Gao ◽  
Jing Li ◽  
Chaofeng Zhang ◽  
...  
Keyword(s):  
Glucose Dehydrogenase ◽  
Value Added ◽  
Microbial Consortia ◽  
Acid Decarboxylase ◽  
Grand Challenge ◽  
Preparative Scale ◽  
E Coli ◽  
Ferulic Acid Decarboxylase ◽  
Cascade Biocatalysis ◽  
Cell Module

Abstract Chiral phenylglycinol is a very important chemical in the pharmaceutical manufacturing. Current methods for synthesis of chiral phenylglycinol often suffered from unsatisfied selectivity, low product yield and using the non-renewable resourced substrates, then the synthesis of chiral phenylglycinol remain a grand challenge. Design and construction of synthetic microbial consortia is a promising strategy to convert bio-based materials to high value-added chiral compounds. In this study, we reported a six-step artificial cascade biocatalysis system for conversion of biobased L-phenylalanine to yield chiral phenylglycinol. The cascade biocatalysis system was conducted by a microbial consortium composed of two engineered recombinant Escherichia coli cells modules, one recombinant E. coli cell module co-expression of six different enzymes (phenylalanine ammonia lyase/ferulic acid decarboxylase/phenylacrylic acid decarboxylase/styrene monooxygenase/epoxide hydrolase/alcohol dehydrogenase) for efficient conversion of L-phenylalanine into 2-hydroxyacetophenone. The second recombinant E. coli cell module expression of an (R)-ω-transaminase or co-expression of the (S)-ω-transaminase, alanine dehydrogenase and glucose dehydrogenase for conversion of 2-hydroxyacetophenone to (S)- or (R)-phenylglycinol, respectively. Combining the two engineered E. coli cell modules, after the optimization of bioconversion conditions (including pH, temperature, glucose concentration, amine donor concentration and cell ratio), L-phenylalanine could be easily converted to (R)-phenylglycinol and (S)-phenylglycinol with up to 99% conversion and >99% ee. Preparative scale biotransformation was also conducted on 100 mL scale, (S)-phenylglycinol and (R)-phenylglycinol were obtained in 71.0% and 80.5% yield, >99% ee, and 5.19 g/L.d and 4.42 g/L.d productivity, respectively. The salient features of this biocatalytic cascade system are good yields, excellent ee, mild reaction conditions and no need for additional cofactor (NADH/NAD+), provide a practical biocatalytic method for sustainable synthesis of (S)-phenylglycinol and (R)-phenylglycinol from biobased L-phenylalanine.

scholarly journals One-pot synthesis of (R)- and (S)-phenylglycinol from bio-based l-phenylalanine by an artificial biocatalytic cascade

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Jiandong Zhang ◽  
Ning Qi ◽  
Lili Gao ◽  
Jing Li ◽  
Chaofeng Zhang ◽  
...  
Keyword(s):  
Glucose Dehydrogenase ◽  
Value Added ◽  
Microbial Consortia ◽  
Acid Decarboxylase ◽  
Grand Challenge ◽  
Preparative Scale ◽  
E Coli ◽  
Ferulic Acid Decarboxylase ◽  
Cell Modules ◽  
Cell Module

AbstractChiral phenylglycinol is a very important chemical in the pharmaceutical manufacturing. Current methods for synthesis of chiral phenylglycinol often suffered from unsatisfied selectivity, low product yield and using the non-renewable resourced substrates, then the synthesis of chiral phenylglycinol remain a grand challenge. Design and construction of synthetic microbial consortia is a promising strategy to convert bio-based materials into high value-added chiral compounds. In this study, we reported a six-step artificial cascade biocatalysis system for conversion of bio-based l-phenylalanine into chiral phenylglycinol. This system was designed using a microbial consortium including two engineered recombinant Escherichia coli cell modules, one recombinant E. coli cell module co-expressed six different enzymes (phenylalanine ammonia lyase/ferulic acid decarboxylase/phenylacrylic acid decarboxylase/styrene monooxygenase/epoxide hydrolase/alcohol dehydrogenase) for efficient conversion of l-phenylalanine into 2-hydroxyacetophenone. The second recombinant E. coli cell module expressed an (R)-ω-transaminase or co-expressed the (S)-ω-transaminase, alanine dehydrogenase and glucose dehydrogenase for conversion of 2-hydroxyacetophenone into (S)- or (R)-phenylglycinol, respectively. Combining the two engineered E. coli cell modules, after the optimization of bioconversion conditions (including pH, temperature, glucose concentration, amine donor concentration and cell ratio), l-phenylalanine could be easily converted into (R)-phenylglycinol and (S)-phenylglycinol with up to 99% conversion and > 99% ee. Preparative scale biotransformation was also conducted on 100-mL scale, (S)-phenylglycinol and (R)-phenylglycinol could be obtained in 71.0% and 80.5% yields, > 99% ee, and 5.19 g/L d and 4.42 g/L d productivity, respectively. The salient features of this biocatalytic cascade system are good yields, excellent ee, mild reaction condition and no need for additional cofactor (NADH/NAD+), provide a practical biocatalytic method for sustainable synthesis of (S)-phenylglycinol and (R)-phenylglycinol from bio-based L-phenylalanine.

scholarly journals Studies on the Preparation of Small 14C Samples with an RGA and 13C-Enriched Material

Radiocarbon ◽  
2010 ◽  
Vol 52 (3) ◽  
pp. 1394-1404 ◽  
Author(s):  
Jakob Liebl ◽  
Roswitha Avalos Ortiz ◽  
Robin Golser ◽  
Florian Handle ◽  
Walter Kutschera ◽  
...  
Keyword(s):  
Sample Preparation ◽  
Test Sample ◽  
Minimum Size ◽  
Test Material ◽  
Reaction Yield ◽  
Side Reactions ◽  
Contamination Level ◽  
Residual Gas ◽  
Contamination Levels ◽  
Physical And Chemical

The minimum size of radiocarbon samples for which reliable results can be obtained in an accelerator mass spectrometry (AMS) measurement is in many cases limited by carbon contamination introduced during sample preparation (i.e. all physical and chemical steps to which samples were subjected, starting from sampling). Efforts to reduce the sample size limit down to a few μg carbon require comprehensive systematic investigations to assess the amount of contamination and the process yields. We are introducing additional methods to speed up this process and to obtain more reliable results. A residual gas analyzer (RGA) is used to study combustion and graphitization reactions. We could optimize the reaction process at small CO2 pressures and identify detrimental side reactions. Knowing the composition of the residual gas in a graphitization process allows a reliable judgment on the completeness of the reaction. Further, we use isotopically enriched 13C (≥98% 13C) as a test material to determine contamination levels. This offers significant advantages: 1) The measurement of 12C/13C in CO2 is possible on-line with the RGA, which significantly reduces turnaround times compared to AMS measurements; 2) Both the reaction yield and the amount of contamination can be determined from a single test sample.The first applications of isotopically enriched 13C and the RGA have revealed that our prototype setup has room for improvements via better hardware; however, significant improvements of our sample processing procedures were achieved, eventually arriving at an overall contamination level of 0.12 to 0.15 μg C during sample preparation (i.e. freeze-drying, combustion, and graphitization) of μg-sized samples in aqueous solution, with above 50% yield.

scholarly journals A Sustainable Approach for Synthesizing (R)-4-Aminopentanoic Acid From Levulinic Acid Catalyzed by Structure-Guided Tailored Glutamate Dehydrogenase

2022 ◽  
Vol 9 ◽  
Author(s):  
Feng Zhou ◽  
Yan Xu ◽  
Xiaoqing Mu ◽  
Yao Nie
Keyword(s):  
Glutamate Dehydrogenase ◽  
Levulinic Acid ◽  
Raw Materials ◽  
Enantiomeric Excess ◽  
Value Added ◽  
Positive Control ◽  
Saturation Mutagenesis ◽  
Structure Comparison ◽  
Amino Donor ◽  
Inorganic Carbonate

In this study, a novel enzymatic approach to transform levulinic acid (LA), which can be obtained from biomass, into value-added (R)-4-aminopentanoic acid using an engineered glutamate dehydrogenase from Escherichia coli (EcGDH) was developed. Through crystal structure comparison, two residues (K116 and N348), especially residue 116, were identified to affect the substrate specificity of EcGDH. After targeted saturation mutagenesis, the mutant EcGDHK116C, which was active toward LA, was identified. Screening of the two-site combinatorial saturation mutagenesis library with EcGDHK116C as positive control, the kcat/Km of the obtained EcGDHK116Q/N348M for LA and NADPH were 42.0- and 7.9-fold higher, respectively, than that of EcGDHK116C. A molecular docking investigation was conducted to explain the catalytic activity of the mutants and stereoconfiguration of the product. Coupled with formate dehydrogenase, EcGDHK116Q/N348M was found to be able to convert 0.4 M LA by more than 97% in 11 h, generating (R)-4-aminopentanoic acid with >99% enantiomeric excess (ee). This dual-enzyme system used sustainable raw materials to synthesize (R)-4-aminopentanoic acid with high atom utilization as it utilizes cheap ammonia as the amino donor, and the inorganic carbonate is the sole by-product.

Aldehyde gold clusters for molecular labeling

1995 ◽  
Vol 53 ◽  
pp. 858-859
Author(s):  
James F. Hainfeld ◽  
Frederic R. Furuya
Keyword(s):  
Covalent Bond ◽  
Aldehyde Group ◽  
Gold Clusters ◽  
Side Reactions ◽  
Amino Groups ◽  
Sodium Cyanoborohydride ◽  
Schiff’S Base ◽  
Protein Molecules ◽  
Hydroxysuccinimide Esters ◽  
Primary Amino

Glutaraldehyde is a useful tissue and molecular fixing reagents. The aldehyde moiety reacts mainly with primary amino groups to form a Schiff's base, which is reversible but reasonably stable at pH 7; a stable covalent bond may be formed by reduction with, e.g., sodium cyanoborohydride (Fig. 1). The bifunctional glutaraldehyde, (CHO-(CH2)3-CHO), successfully stabilizes protein molecules due to generally plentiful amines on their surface; bovine serum albumin has 60; 59 lysines + 1 α-amino. With some enzymes, catalytic activity after fixing is preserved; with respect to antigens, glutaraldehyde treatment can compromise their recognition by antibodies in some cases. Complicating the chemistry somewhat are the reported side reactions, where glutaraldehyde reacts with other amino acid side chains, cysteine, histidine, and tyrosine. It has also been reported that glutaraldehyde can polymerize in aqueous solution. Newer crosslinkers have been found that are more specific for the amino group, such as the N-hydroxysuccinimide esters, and are commonly preferred for forming conjugates. However, most of these linkers hydrolyze in solution, so that the activity is lost over several hours, whereas the aldehyde group is stable in solution, and may have an advantage of overall efficiency.

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