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Results for “biocatalysis”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Photoinduced chemomimetic biocatalysis for enantioselective intermolecular radical conjugate addition

Exploiting nature’s catalysts for non-natural transformations that are inaccessible to chemocatalysis is highly desirable but challenging. On the one hand, the widespread nicotinamide-dependent oxidoreductases have not been utilized for single-electron-transfer-induced bimolecular cross-couplings; on the other, the addition of catalytic asymmetric radical con- jugate to terminal alkenes remains a challenge owing to strong racemic background reaction and unselective termination of prochiral radical species. Here we report a chemomimetic biocatalysitic approach for construction of alpha-carbonyl stereocentres via an unnatural intermolecular conjugate addition of N-(acyloxy)phthalimides-derived radicals with acceptor-substituted terminal alkenes, by combination of visible-light excitation and nicotinamide-dependent ketoreductases (KREDs). Based on protein crystal structure, we engineered KREDs via a semi-rational mutagenesis strategy to improve reaction outcomes with a small and high-quality variants library. Here, mechanistic investigations combining wet experiments, crystallographic studies and computational simulations demonstrate that the repurposed biocatalyst can suppress racemic background reaction and unselected side reactions, yielding enantioselectivity that is challenging to achieve by chemocatalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Editorial: Cell Free Biocatalysis for the Production of Bioproducts

Biological approaches show promise for the sustainable and cost competitive production of commodity fuels and chemicals. A lot of efforts have been devoted to engineering microbial chassis to produce select fuels and chemicals. These approaches have had some level of success exemplified, of course, by the production of ethanol at high yield and titer but also recent successes with commodity chemicals such as 1,4-butanediol, 1,3-propanediol, and even to some extent with sustainable aviation fuel intermediates such as farnesene. However, many of these processes still suffer from low yields, usually below the standard needed to drive a sustainable and atom efficient bioeconomy. Additionally, for many other chemicals and fuel precursors, titers and yields are only a fraction of what they are for ethanol. Indeed, there exist many limiting factors associated with the use of microbial biocatalysts. Some of these factors include the diversion of carbon from products to sustain growth and biomass formation, the production of byproducts or regulatory mechanisms, the toxicity of end products or intermediates, and the difficulty of separating products from growth media.

09 BIOMASS FUELS↗
DOE OSTI2024

Long-Term Stability of Nicotinamide Cofactors in Common Aqueous Buffers: Implications for Cell-Free Biocatalysis

The use of nicotinamide cofactors in cell-free biocatalytic systems is necessitated by the high specificity that these enzymes show for their natural redox mediators. Unfortunately, isolation and use of natural cofactors is costly, which suggests that enhancing their stability is key to enabling their use in industrial processes. This study details NAD+ and NADH stability in three buffer systems (sodium phosphate, HEPES, and Tris) at 19 °C and 25 °C and for up to 43 d. In Tris, both NADH and NAD+ were found to be highly stable. NADH degradation rates of 4 μM/d (19 °C) and 11 μM/d (25 °C) were observed in Tris buffer, corresponding to >90% and 75% remaining after 43 d, respectively. Higher degradation rates (up to 34 μM/d) were observed when sodium phosphate or HEPES buffers were used. The effect of a mild increase in temperature was determined to be significant for long-term stability, and it was shown that degradation under these conditions can be easily monitored via UV–Vis, because the degradation proceeds via the oxidation/de-aromatization of the dihydropyridine ring. Overall, this work emphasizes that the choice of buffer system is consequential for bioreactor systems employing natural nicotinamide cofactors for extended periods of time.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1983

ECUT: Energy Conversion and Utilization Technologies program biocatalysis research activity. Potential membrane applications to biocatalyzed processes: Assessment of concentration polarization and membrane fouling

Separation and purification of the products of biocatalyzed fermentation processes, such as ethanol or butanol, consumes most of the process energy required. Since membrane systems require substantially less energy for separation than most alternatives (e.g., distillation) they have been suggested for separation or concentration of fermentation products. This report is a review of the effects of concentration polarization and membrane fouling for the principal membrane processes: microfiltration, ultrafiltration, reverse osmosis, and electrodialysis including a discussion of potential problems relevant to separation of fermentation products. It was concluded that advanced membrane systems may result in significantly decreased energy consumption. However, because of the need to separate large amounts of water from much smaller amounts of product that may be more volatile than wate, it is not clear that membrane separations will necessarily be more efficient than alternative processes.

Ingham, J. D.↗
NASA NTRS1983

ECUT: Energy Conversion and utilization Technologies program biocatalysis research activity. Generation of chemical intermediates by catalytic oxidative decarboxylation of dilute organic acids

A rhodium-based catalyst was prepared and preliminary experiments were completed where the catalyst appeared to decarboxylate dilute acids at concentrations of 1 to 10 vol%. Electron spin resonance spectroscoy was used to characterize the catalyst as a first step leading toward modeling and optimization of rhodium catalysts. Also, a hybrid chemical/biological process for the production of hydrocarbons has been assessed. These types of catalysts could greatly increase energy efficiency of this process.

Distefano, S.↗
DOE OSTI2023

Production of fusel lactates via biocatalysis

Microbial enzymes are used for esterification of biomass-derived substrates for production of industrially valuable esters. E. coli was used as an efficient platform for recombinant synthesis of fusel lactates such as the green solvent ethyl lactate.

Davis, Ryan Wesley↗
DOE OSTI2022

Photobiocatalysis for Abiological Transformations

Harnessing biocatalysts for novel abiological transformations is a longstanding goal of synthetic chemistry. Combining the merits of biocatalysis and photocatalysis allows for selective transformations fueled by visible light and offers many advantages including new reactivity, high enantioselectivity, greener syntheses, and high yields. Photoinduced electron or energy transfer enables synthetic methodologies that complement conventional two electron processes or offer orthogonal pathways for developing new reactions. Enzymes are well suited and can be tuned by directed evolution to exert control over radical intermediates thereby suppressing undesirable reactions and delivering high chemo- and stereoselectivities. Within the past decade, the combination of biocatalysis and photocatalysis was mainly focused on exploiting light-regenerated cofactors to increase native enzymatic activity. However, recent developments have demonstrated that the combination can unlock new-to-nature chemistry. Particularly, the discovery and application of new strategies are well poised to expand the applications of photobiocatalysis. In the past three years, our lab has been studying the combinations of photocatalysis and biocatalysis which can be applied to create new synthetic methodologies and solve challenges in synthetic organic chemistry. Our efforts have expanded the strategies for combining external photocatalysts with enzymes through the construction of a synergistic cooperative stereoconvergent reduction system consisting of photosensitized energy transfer and ene-reductase catalyzed alkene reduction. Additionally, our efforts have also extended the capability of cofactor-dependent photoenzymatic systems to include enantioselective bimolecular radical hydroalkylations of alkenes by irradiating electron donor-acceptor complexes comprised of enzymatic redox active cofactors and unnatural substrates. In this Account, we highlight strategies developed by our group and others for combining biocatalysis and photocatalysis with the aim of introducing nonnatural reactivity to enzymes. Presently, strategies applied to achieve this goal include the repurposing of newly discovered photoactive enzymes, the elucidation of new photoreactivity within cofactor-dependent enzymes, the combination of external photocatalysts with enzymes, and the construction of artificial photoenzymes. By demonstrating the successful application of these strategies for achieving selective new-to-nature transformations, we hope to spur interest in the expanding the scope of photobiocatalytic systems through the use and extension of these strategies and creation of new strategies. In addition, we hope to elucidate the intuition in synergizing the unique capabilities of biocatalysis and photocatalysis so that photobiocatalysis can be recognized as a potential solution to difficult challenges in synthetic organic chemistry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Catalytic bias in oxidation–reduction catalysis

Cataytic bias refers to the propensity of a reaction catalyst to effect a different rate acceleration in one direction versus the other in a chemical reaction under non-equilibrium conditions. In biocatalysis, the inherent bias of an enzyme is often advantagous to augment the innate thermodynamics of a reaction to promote efficiency and fidelity in the coordination of catabolic and anabolic pathways. In industrial chemical catalysis a directional cataltyic bias is a sought after property in facilitating the engineering of systems that couple catalysis with harvest and storage of for example fine chemicals or energy compounds. Interestingly, there is little information about catalytic bias in biocatalysis likely in large part due to difficulties in developing tractible assays sensitive enough to study detailed kinetics. For oxidation–reduction reactions, colorimetric redox indicators exist in a range of reduction potentials to provide a mechanism to study both directions of reactions in a fairly facile manner. The current short review attempts to define catalytic bias conceptually and to develop model systems for defining the parameters that control catalytic bias in enzyme catalyzed oxidation–reduction catalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Light‐driven catalysis with engineered enzymes and biomimetic systems

Abstract Efforts to drive catalytic reactions with light, inspired by natural processes like photosynthesis, have a long history and have seen significant recent growth. Successfully engineering systems using biomolecular and bioinspired catalysts to carry out light‐driven chemical reactions capitalizes on advantages offered from the fields of biocatalysis and photocatalysis. In particular, driving reactions under mild conditions and in water, in which enzymes are operative, using sunlight as a renewable energy source yield environmentally friendly systems. Furthermore, using enzymes and bioinspired systems can take advantage of the high efficiency and specificity of biocatalysts. There are many challenges to overcome to fully capitalize on the potential of light‐driven biocatalysis. In this mini‐review, we discuss examples of enzymes and engineered biomolecular catalysts that are activated via electron transfer from a photosensitizer in a photocatalytic system. We place an emphasis on selected forefront chemical reactions of high interest, including CH oxidation, proton reduction, water oxidation, CO 2 reduction, and N 2 reduction.

Edwards, Emily H.↗
DOE OSTI2022

Designing an innovation system to support profitable electro- and bio-catalytic carbon upgrade

Carbon capture, utilisation, and storage (CCUS) can mitigate an estimated 14–20% of CO 2 emissions by 2050. Here, we evaluate an integrated electrocatalysis and biocatalysis CCUS pathway, using externally-supplied renewable electricity to convert over 12 MtCO 2 to poly(3-hydroxybutyrate) via methanol and formate intermediates. A techno-economic and policy-innovation analysis provides insight into global CCUS innovation. Results suggest that innovation should focus on improving methanol faradaic efficiency, formate biocatalysis efficiency, electrocatalysis current density, and catalyst performance. Methanol and formate composition influences performance, but higher formate content can improve economics by US$3.8B over a 30 year lifetime. Profitable scenarios hinge on reducing methanol separation costs – through innovation or reduced energy usage – along with cheap renewable electricity and/or carbon pricing. Our evaluation of the global innovation status signifies that coordinated strategies are required to realise emissions cuts from CCUS. Innovation can be spurred by targeted investments and policies that promote emissions reductions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

pH- and Redox-Responsive Pickering Emulsions Based on Cellulose Nanocrystal Surfactants

Nanoparticle surfactants (NPSs), formed by using dynamic interactions between nanoparticles and complementary ligands at the liquid-liquid interface, have emerged as “smart emulsifiers” with attributes of high emulsification efficiency, long-term stability, and on-demand emulsification/demulsification capabilities. However, only pH-responsiveness can be adopted for the assembly of reported NPSs formed by electrostatic interactions. Here, we propose an alternative design strategy, by taking advantage of the ferrocenium (Fc + ) sulfate ion pair, to develop a new type of cellulose nanocrystal (CNC) surfactant. In conclusion, the Fc + groups are sensitive to pH, redox reagents and voltage, imparting the CNC surfactants and derived Pickering emulsions with multi-stimuli-responsiveness, and showing promising applications in controllable delivery, release, and biphasic biocatalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Enhancing 2‐Pyrone Synthase Efficiency by High‐Throughput Mass‐Spectrometric Quantification and In Vitro/In Vivo Catalytic Performance Correlation

Abstract Engineering efficient biocatalysts is essential for metabolic engineering to produce valuable bioproducts from renewable resources. However, due to the complexity of cellular metabolic networks, it is challenging to translate success in vitro into high performance in cells. To meet such a challenge, an accurate and efficient quantification method is necessary to screen a large set of mutants from complex cell culture and a careful correlation between the catalysis parameters in vitro and performance in cells is required. In this study, we employed a mass‐spectrometry based high‐throughput quantitative method to screen new mutants of 2‐pyrone synthase (2PS) for triacetic acid lactone (TAL) biosynthesis through directed evolution in E. coli . From the process, we discovered two mutants with the highest improvement (46 fold) in titer and the fastest k cat (44 fold) over the wild type 2PS, respectively, among those reported in the literature. A careful examination of the correlation between intracellular substrate concentration, Michaelis‐Menten parameters and TAL titer for these two mutants reveals that a fast reaction rate under limiting intracellular substrate concentrations is important for in‐cell biocatalysis. Such properties can be tuned by protein engineering and synthetic biology to adopt these engineered proteins for the maximum activities in different intracellular environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Mechanisms in the Synthesis of S -Alcohols with 1,4-NADH Biomimetic Co-factor N-Benzyl-1,4-dihydronicotinamide using Horse Liver Alcohol Dehydrogenase: A Hybrid Computational Study

The enantioselective reduction of prochiral ketones catalyzed by horse liver alcohol dehydrogenase (HLADH), was investigated via a hybrid computational approach, for molecular reactions involved in chiral synthesis of S-alcohols, when the natural co-factor, 1,4-dihyronicotinamide adenine dinucleotide, 1,4-NADH, was replaced with biomimetic co-factor, N-benzyl-1,4-dihydronicotinamide, 1. We surmised that different hydride and proton transfer mechanisms were involved using co-factor, 1. An alternative mechanism, where the hydride transfer step occurred, via an η 1 -keto-S-η 2 -5,6-1,4-dihydronicotinamide-Zn(II) complex, was previously investigated with a model of the HLADH-Zn(II) catalytic site (J. Organometal. Chem. 2021, 943, 121810). Presently, we studied canonical and alternative mechanisms compared to models of the entire enzyme structure. We disproved the η 2 -Zn(II) complex, and discovered a canonical hydride transfer from biomimetic 1,4-NADH, 1, to the Zn(II) bound prochiral ketone substrate, followed by a new proton relay, consisting of a water chain connecting His51 to Ser48 that accomplished the S-alkoxy anion's protonation to yield the final S-alcohol product. The HLADH catalysis, with biomimetic co-factor, 1, that replaced the ribose group, the 5'-diphosphate groups, and the adenine nucleotide with a N-benzyl group, has provided a new paradigm for the design of other structures of 1,4-NADH biomimetic co-factors, including their economic value in biocatalysis reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Mixed lipid bilayers enable enhanced stability and activity retention of Lipase A in low-pH environments

Lipase A (LipA) from Bacillus subtilis is a versatile and industrially relevant enzyme, but its activity is compromised under acidic conditions due to aggregation and deactivation. In this study, we investigated the use of mixed lipid bilayers to stabilize and improve activity retention of LipA at low pH. Attachment to lipid bilayers, particularly those containing cationic lipids, greatly enhanced the long-term stability of LipA in acidic conditions while also leading to improvements in activity. Tethering to cationic bilayers not only shifted the apparent pH activity profile toward more acidic conditions, but also significantly enhanced activity retention upon incubation at pH 6. Notably, this protective effect persisted even without direct tethering, indicating that reversible, non-covalent interactions with the bilayer surface are sufficient for long-term stability. Circular dichroism further revealed that the secondary structure of LipA was retained, while dynamic light scattering suggested that activity loss in solution was primarily due to aggregation of the native state. Together, these findings support a model in which lipid bilayers mitigate aggregation and stabilize LipA through transient interactions and electrostatic modulation of the local surface environment. Furthermore, this approach exemplifies a simple, tether-free strategy for enhancing enzyme performance in acidic or destabilizing conditions, with implications for biocatalysis, biosensing, and therapeutic delivery.

Biocatalysis↗
DOE OSTI2023

Combinatorial gene inactivation of aldehyde dehydrogenases mitigates aldehyde oxidation catalyzed by E. coli resting cells

Aldehydes are attractive chemical targets both as end products in the flavors and fragrances industry and as synthetic intermediates due to their propensity for C–C bond formation. Here, in this study, we identify and address unexpected oxidation of a model collection of aromatic aldehydes, including many that originate from biomass degradation. When diverse aldehydes are supplemented to E. coli cells grown under aerobic conditions, as expected they are either reduced by the wild-type MG1655 strain or stabilized by a strain engineered for reduced aromatic aldehyde reduction (the E. coli RARE strain). Surprisingly, when these same aldehydes are supplemented to resting cell preparations of either E. coli strain, under many conditions we observe substantial oxidation. By performing combinatorial inactivation of six candidate aldehyde dehydrogenase genes in the E. coli genome using multiplexed automatable genome engineering (MAGE), we demonstrate that this oxidation can be substantially slowed, with greater than 50% retention of 6 out of 8 aldehydes when assayed 4 h after their addition. Given that our newly engineered strain exhibits reduced oxidation and reduction of aromatic aldehydes, we dubbed it the E. coli ROAR strain. We applied the new strain to resting cell biocatalysis for two kinds of reactions – the reduction of 2-furoic acid to furfural and the condensation of 3-hydroxybenzaldehyde and glycine to form a non-standard β-hydroxy-α-amino acid. In each case, we observed substantial improvements in product titer 20 h after reaction initiation (9-fold and 10-fold, respectively). Moving forward, the use of this strain to generate resting cells should allow aldehyde product isolation, further enzymatic conversion, or chemical reactivity under cellular contexts that better accommodate aldehyde toxicity.

59 BASIC BIOLOGICAL SCIENCES↗