title: Cascade catalysis in membranes with enzyme immobilization for multi-enzymatic conversion of CO2 to methanol.
abstract: Facile co-immobilization of enzymes is highly desirable for bioconversion methods involving multi-enzymatic cascade reactions. Here we show for the first time that three enzymes can be immobilized in flat-sheet polymeric membranes simultaneously or separately by simple pressure-driven filtration (i.e. by directing membrane fouling formation), without any addition of organic solvent. Such co-immobilization and sequential immobilization systems were examined for the production of methanol from CO2 with formate dehydrogenase (FDH), formaldehyde dehydrogenase (FaldDH) and alcohol dehydrogenase (ADH). Enzyme activity was fully retained by this non-covalent immobilization strategy. The two immobilization systems had similar catalytic efficiencies because the second reaction (formic acid→formaldehyde) catalyzed by FaldDH was found to be the cascade bottleneck (a threshold substrate concentration was required). Moreover, the trade-off between the mitigation of product inhibition and low substrate concentration for the adjacent enzymes probably made the co-immobilization meaningless. Thus, sequential immobilization could be used for multi-enzymatic cascade reactions, as it allowed the operational conditions for each single step to be optimized, not only during the enzyme immobilization but also during the reaction process, and the pressure-driven mass transfer (flow-through mode) could overcome the diffusion resistance between enzymes. This study not only offers a green and facile immobilization method for multi-enzymatic cascade systems, but also reveals the reaction bottleneck and provides possible solutions for the bioconversion of CO2 to methanol.
authors.affiliation: Department of Chemical and Biochemical Engineering, Center for BioProcess Engineering, Building 229, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark. Electronic address: jqluo@ipe.ac.cn.
authors.forename: Jianquan
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Chemical and Biochemical Engineering, Center for BioProcess Engineering, Building 229, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Anne S
authors.initials: AS
authors.lastname: Meyer
authors.affiliation: Center for Electron Nanoscopy, Danchip, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: R V
authors.initials: RV
authors.lastname: Mateiu
authors.affiliation: Department of Chemical and Biochemical Engineering, Center for BioProcess Engineering, Building 229, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark. Electronic address: mp@kt.dtu.dk.
authors.forename: Manuel
authors.initials: M
authors.lastname: Pinelo
mesh_terms: D000426:Alcohol Dehydrogenase / Q000737:chemistry; D000445:Aldehyde Oxidoreductases / Q000737:chemistry; D000818:Animals; D002175:Candida / Q000378:metabolism; D002245:Carbon Dioxide / Q000737:chemistry*; D002384:Catalysis; D002417:Cattle; D004800:Enzymes, Immobilized / Q000737:chemistry*; D005560:Formate Dehydrogenases / Q000737:chemistry; D008099:Liver / Q000201:enzymology; D000432:Methanol / Q000737:chemistry*; D009243:NAD / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011312:Pressure; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D012997:Solvents / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D004800:Enzymes, Immobilized; D011108:Polymers; D012997:Solvents; D009243:NAD; D002245:Carbon Dioxide; D000426:Alcohol Dehydrogenase; D005560:Formate Dehydrogenases; D000445:Aldehyde Oxidoreductases; C087006:formaldehyde dehydrogenase, glutathione-independent; D000432:Methanol