Improving the catalytic activity of formate dehydrogenase from Candida boidinii by using magnetic nanoparticles

Creating NADP+ -Specific Formate Dehydrogenases from Komagataella phaffii by Enzymatic Engineering

Most natural formate dehydrogenases (FDHs) exhibit NAD+ specificity, making it imperative to explore the engineering of FDH cofactor specificity for NADPH regeneration systems. The endogenous FDH of Komagataella phaffii (K. phaffii), termed KphFDH, is a typical NAD+ -specific FDH. However, investigations into engineering the cofactor specificity of KphFDH have yet to be conducted. To develop an NADP+ -specific variant of KphFDH, we selected D195, Y196, and Q197 as mutation sites and generated twenty site-directed variants. Through kinetic characterization, KphFDH/V19 (D195Q/Y196R/Q197H) was identified as the variant with the highest specificity towards NADP+ , with a ratio of catalytic efficiency (kcat /KM )NADP+ /(kcat /KM )NAD+ of 129.226. Studies of enzymatic properties revealed that the optimal temperature and pH for the reduction reaction of NADP+ catalyzed by KphFDH/V19 were 45 °C and 7.5, respectively. The molecular dynamics (MD) simulation was performed to elucidate the mechanism of high catalytic activity of KphFDH/V19 towards NADP+ . Finally, KphFDH/V19 was applied to an in vitro NADPH regeneration system with Meso-diaminopimelate dehydrogenase from Symbiobacterium thermophilum (StDAPDH/H227V). This study successfully created a KphFDH variant with high NADP+ specificity and demonstrated its practical applicability in an in vitro NADPH regeneration system.

The challenges of using NAD+-dependent formate dehydrogenases for CO2 conversion

In recent years, CO₂ reduction and utilization have been proposed as an innovative solution for global warming and the ever-growing energy and raw material demands. In contrast to various classical methods, including chemical, electrochemical, and photochemical methods, enzymatic methods offer a green and sustainable option for CO₂ conversion. In addition, enzymatic hydrogenation of CO₂ into platform chemicals could be used to produce economically useful hydrogen storage materials, making it a win-win strategy. The thermodynamic and kinetic stability of the CO₂ molecule makes its utilization a challenging task. However, Nicotine adenine dinucleotide (NAD⁺)-dependent formate dehydrogenases (FDHs), which have high selectivity and specificity, are attractive catalysts to overcome this issue and convert CO₂ into fuels and renewable chemicals. It is necessary to improve the stability, cofactor necessity, and CO₂ conversion efficiency of these enzymes, such as by combining them with appropriate hybrid systems. However, metal-independent, NAD⁺-dependent FDHs, and their CO₂ reduction activity have received limited attention to date. This review outlines the CO₂ reduction ability of these enzymes as well as their properties, reaction mechanisms, immobilization strategies, and integration with electrochemical and photochemical systems for the production of formic acid or formate. The biotechnological applications of FDH, future perspectives, barriers to CO₂ reduction with FDH, and aspects that must be further developed are briefly summarized. We propose that constructing hybrid systems that include NAD⁺-dependent FDHs is a promising approach to convert CO₂ and strengthen the sustainable carbon bio-economy.

Enzymatic characteristics of immobilized carbonic anhydrase and its applications in CO2 conversion

Native carbonic anhydrase (CA) has been widely used in several different applications due to its catalytic function in the interconversion of carbon dioxide (CO₂) and carbonic acid. However, subject to its stability and recyclability, native CA often deactivates when in harsh environments, which restricts its applications in the commercial market. Maintaining the stability and high catalytic activity of CA is challenging. Immobilization provides an effective route that can improve enzymatic stability. Through the interaction of covalent bonds and van der Waals forces, water-soluble CA can be combined with various insoluble supports to form water-insoluble immobilized CA so that CA stability and utilization can be greatly improved. However, if the immobilization method or immobilization condition is not suitable, it often leads to a decrease in CA activity, reducing the application effects on CO₂ conversion. In this review, we discuss existing immobilization methods and applications of immobilized CA in the environmental field, such as the mineralization of carbon dioxide and multienzyme cascade catalysis based on CA. Additionally, prospects in current development are outlined. Because of the many outstanding and superior properties after immobilization, CA is likely to be used in a wide variety of scientific and technical areas in the future.

Facile preparation of aminosilane-alginate hybrid beads for enzyme immobilization: Kinetics and equilibrium studies

A simple, facile and potential platform for enzyme immobilization using alginate-based beads has been demonstrated by simultaneous gelation and modification of alginate using calcium chloride (CaCl₂) and 3-aminopropyltriethoxysilane (APTES). In this method, sodium alginate solution containing enzyme was simply dripped into a crosslinker solution containing CaCl₂ and APTES, leading to the formation of APTES-alginate hybrid beads (AP-beads). The optical observation, FT-IR analysis and amino group measurements provided evidence that APTES was successfully adsorbed to the alginate chain via electrostatic interaction. On the assumption that the binding of Ca²⁺ ion to polymannuronate residues of alginate via bidentate bridging coordination is competitive with APTES, the equilibrium isotherm and kinetics for the adsorption of APTES to AP-beads was found to follow extended Langmuir isotherm in binary system. Formate dehydrogenase (FDH) as a model enzyme was successfully immobilized in AP-beads and the immobilization yield of ca. 100% could be achieved under optimal conditions of CaCl₂ and APTES concentrations in crosslinker solution. Furthermore, the AP-beads were reused efficiently for 9 cycles without loss of FDH activity. The above results demonstrated that AP-beads were effective support for enzyme immobilization.

High-Level Production of 4-Hydroxyvalerate from Levulinic Acid via Whole-Cell Biotransformation Decoupled from Cell Metabolism

γ-Hydroxyvalerate (4HV) is an important monomer used to produce various valuable polymers and products. In this study, an engineered 3-hydroxybutyrate dehydrogenase that can convert levulinic acid (LA) into 4HV was co-expressed with a cofactor (NADH) regeneration system mediated by an NAD⁺-dependent formate dehydrogenase (CbFDH) in the Escherichia coli strain, MG1655. The resulting strain produced 23-fold more 4HV in a shake flask. The 4HV production was not dependent on ATP and required low aeration; all of these are considered beneficial characteristics for the production of target compounds, especially at an industrial scale. Under optimized conditions in a 5 L fermenter, the titer, productivity, and molar conversion efficiency for 4HV reached 100 g/L, 4.2 g/L/h, and 92%, respectively. Our system could prove to be a promising method for the large-scale production of 4HV from LA at low-cost and using a renewable biomass source.

Influence of Dlutaraldehyde Cross-Linking Modes on the Recyclability of Immobilized Lipase B from Candida antarctica for Transesterification of Soy Bean Oil

Lipase B from Candida antarctica (CAL-B) is largely employed as a biocatalyst for hydrolysis, esterification, and transesterification reactions. CAL-B is a good model enzyme to study factors affecting the enzymatic structure, activity and/or stability after an immobilization process. In this study, we analyzed the immobilization of CAL-B enzyme on different magnetic nanoparticles, synthesized by the coprecipitation method inside inverse micelles made of zwitterionic surfactants, with distinct carbon chain length: 4 (ImS4), 10 (ImS10) and 18 (ImS18) carbons. Magnetic nanoparticles ImS4 and ImS10 were shown to cross-link to CAL-B enzyme via a Michael-type addition, whereas particles with ImS18 were bond via pyridine formation after glutaraldehyde cross-coupling. Interestingly, the Michael-type cross-linking generated less stable immobilized CAL-B, revealing the influence of a cross-linking mode on the resulting biocatalyst behavior. Curiously, a direct correlation between nanoparticle agglomerate sizes and CAL-B enzyme reuse stability was observed. Moreover, free CAL-B enzyme was not able to catalyze transesterification due to the high methanol concentration; however, the immobilized CAL-B enzyme reached yields from 79.7 to 90% at the same conditions. In addition, the transesterification of lipids isolated from oleaginous yeasts achieved 89% yield, which confirmed the potential of immobilized CAL-B enzyme in microbial production of biodiesel.

Identification of catalysis, substrate, and coenzyme binding sites and improvement catalytic efficiency of formate dehydrogenase from Candida boidinii

Formate dehydrogenases (FDHs) are continually used for the cofactor regeneration in biocatalysis and biotransformation with hiring NAD(P)H-dependent oxidoreductases. Major weaknesses of most native FDHs are their low activity and operational stability in the catalytic reaction. In this work, the FDH from Candida boidinii (CboFDH) was engineered in order to gain an enzyme with high activity and better operational stability. Through comparing and analyzing its spatial structure with other FDHs, the catalysis, substrate, and coenzyme binding sites of the CboFDH were identified. To improve its performance, amino acids, which concentrated on the enzyme active site or in the conserved NAD(+) and substrate binding motif, were mutated. The mutant V120S had the highest catalytic efficiency (k cat/K m ) with COONH4 as it enhanced the catalytic velocity (k cat) and k cat/K m 3.48-fold and 1.60-fold, respectively, than that of the wild type. And, the double-mutant V120S-N187D had the highest k cat/K m with NAD(+) as it displayed an approximately 1.50-fold increase in k cat/K m . The mutants showed higher catalytic efficiency than other reported FDHs, suggesting that the mutation has achieved good results. The single and double mutants exhibited higher thermostability than the wild type. The structure-function relationship of single and double mutants was analyzed by homology models and site parsing. Asymmetric synthesis of L-tert-leucine was executed to evaluate the ability of cofactor regeneration of the mutants with about 100 % conversion rates. This work provides a helpful theoretical reference for the evolution of an enzyme in vitro and promotion of the industrial production of chiral compounds, e.g., amino acid and chiral amine.

Highly stable and reusable immobilized formate dehydrogenases: Promising biocatalysts for in situ regeneration of NADH

This study aimed to prepare robust immobilized formate dehydrogenase (FDH) preparations which can be used as effective biocatalysts along with functional oxidoreductases, in which in situ regeneration of NADH is required. For this purpose, Candida methylica FDH was covalently immobilized onto Immobead 150 support (FDHI150), Immobead 150 support modified with ethylenediamine and then activated with glutaraldehyde (FDHIGLU), and Immobead 150 support functionalized with aldehyde groups (FDHIALD). The highest immobilization yield and activity yield were obtained as 90% and 132%, respectively when Immobead 150 functionalized with aldehyde groups was used as support. The half-life times (t_1/2) of free FDH, FDHI150, FDHIGLU and FDHIALD were calculated as 10.6, 28.9, 22.4 and 38.5 h, respectively at 35 °C. FDHI150, FDHIGLU and FDHIALD retained 69, 38 and 51% of their initial activities, respectively after 10 reuses. The results show that the FDHI150, FDHIGLU and FDHIALD offer feasible potentials for in situ regeneration of NADH.

Association of Pseudomonas putida formaldehyde dehydrogenase with superparamagnetic nanoparticles: an effective way of improving the enzyme stability, performance and recycling

The association of formaldehyde dehydrogenase fromPseudomonas putida(FalDH) with two different magnetic nanoparticles led to distinct enzyme responses depending upon the chemical modification process applied.