Chimeric versus isolated proteins: Biochemical characterization of the NADP+-dependent formate dehydrogenase from Pseudomonas sp. 101 fused with the Baeyer-Villiger monooxygenase from Thermobifida fusca

The expression of multifunctional proteins can facilitate the setup of a biotechnology process that requires multiple functions absolved by different proteins. Herein the functional and conformational characterization of a formate dehydrogenase-monooxygenase chimera enzyme is presented. The fused enzyme (FDH-PAMO) was prepared by linking the C-terminus of the mutant NADP+-dependent formate dehydrogenase from Pseudomonas sp. 101 (FDH) to the N-terminus of the NADPH-dependent monooxygenase from Thermobifida fusca (PAMO) through a peptide linker of 9 amino acids (ASGGGGSGT) generating a chimera protein of 107,056 Da. The catalytic properties (e.g., kinetic parameters kcat and Km), stability, fluorescence and circular dichroism spectra showed that the so-obtained chimera enzyme FDH-PAMO retains the same functional and conformational properties of the two parental enzymes. Furthermore, SEC chromatographic analysis indicated that, in solution (pH 7.4), FDH-PAMO assembles to tetramers (up to 4.2 %) due to the propensity of FDH and PAMO to form dimers, up to 96.6 % and 6.2 %, respectively. This study provides valuable insights into the structural stability of a thermostable protein (e.g., PAMO) after increasing its size through fusion with another similarly sized thermostable protein (e.g., FDH).

Functionalized Ionic Liquids for CO2 Capture under Ambient Pressure

Ionic liquids (ILs) have been widely explored as alternative solvents for carbon dioxide (CO2) capture and utilization. However, most of these processes are under pressures significantly higher than atmospheric level, which not only levies additional equipment and operation costs, but also makes the large-scale CO2 capture and conversion less practical. In this study, we rationally designed glycol ether-functionalized imidazolium, phosphonium and ammonium ILs containing acetate (OAc-) or Tf2N- anions, and found these task-specific ILs could solubilize up to 0.55 mol CO2 per mole of IL (or 5.9 wt% CO2) at room temperature and atmospheric pressure. Although acetate anions enabled a better capture of CO2, Tf2N- anions are more compatible with alcohol dehydrogenase (ADH), which is a key enzyme involved in the cascade enzymatic conversion of CO2 to methanol. Our promising results indicate the possibility of CO2 capture under ambient pressure and its enzymatic conversion to valuable commodity.

Surface Interaction of Ionic Liquids: Stabilization of Polyethylene Terephthalate-Degrading Enzymes in Solution

The effect of aqueous solutions of selected ionic liquids solutions on Ideonella sakaiensis PETase with bis(2-hydroxyethyl) terephthalate (BHET) substrate were studied by means of molecular dynamics simulations in order to identify the possible effect of ionic liquids on the structure and dynamics of enzymatic Polyethylene terephthalate (PET) hydrolysis. The use of specific ionic liquids can potentially enhance the enzymatic hydrolyses of PET where these ionic liquids are known to partially dissolve PET. The aqueous solution of cholinium phosphate were found to have the smallest effect of the structure of PETase, and its interaction with (BHET) as substrate was comparable to that with the pure water. Thus, the cholinium phosphate was identified as possible candidate as ionic liquid co-solvent to study the enzymatic hydrolyses of PET.

Ionic liquids for regulating biocatalytic process: Achievements and perspectives

Biocatalysis has found enormous applications in sorts of fields as an alternative to chemical catalysis. In the pursue of green and sustainable chemistry, ionic liquids (ILs) have been considered as promising reaction media for biocatalysis, owing to their unique characteristics, such as nonvolatility, inflammability and tunable properties as regards polarity and water miscibility behavior, compared to organic solvents. In recent years, great developments have been achieved in respects to biocatalysis in ILs, especially for preparing various chemicals. This review tends to give illustrative examples with a focus on representative chemicals production by biocatalyst in ILs and elucidate the possible mechanism in such systems. It also discusses how to regulate the catalytic efficiency from several aspects and finally provides an outlook on the opportunities to broaden biocatalysis in ILs.

Visible-light-driven CO2 reduction to formate with a system of water-soluble zinc porphyrin and formate dehydrogenase in ionic liquid/aqueous media

Visible-light-driven CO₂ reduction to formate with a system consisting of water-soluble zinc tetraphenylporphyrin tetrasulfonate (ZnTPPS), formate dehydrogenase from Candida boidinii (CbFDH) and methylviologen (MV) in the presence of triethanolamine (TEOA) as an electron donor in an ionic liquid, 1-ethyl-3-methylimidazolium dimethyl phosphate ([EMlm][Me₂PO₄])/aqueous media was investigated. The catalytic activity of CbFDH for formate oxidation to CO₂ and CO₂ reduction to formate did not decrease significantly even in [EMlm][Me₂PO₄]/aqueous media, compared with that in aqueous media. The visible-light-driven MV reduction by the photosensitization of ZnTPPS in [EMlm][Me₂PO₄]/aqueous media proceeds more efficiently than in the aqueous media system. In the visible-light-driven CO₂ reduction to formate system of ZnTPPS, MV and CbFDH with [EMlm][Me₂PO₄]/aqueous media, moreover, the formate production concentration after 180 min decreased by only 20% as compared with the system in aqueous media.