Biocatalytic Applications

Faber, Kurt

doi:10.1007/978-3-642-17393-6_2

Cited by 18 publications

(8 citation statements)

References 1,606 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the enzymatic reaction cycle, NADH serves as hydrogen donor with a resultant oxidation to NAD + , as illustrated by pathway a in Figure . Given the high cost of NADH (bulk price per mole: USD $3,000), a stoichiometric supply for commercial enzymatic transformations is not economically feasible and regeneration (NAD + → NADH, pathway b in Figure ) is required. Coupled-enzyme methodologies employ two separate enzymes for substrate → product reduction and cofactor regeneration .…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous Catalysis Mediated Cofactor NADH Regeneration for Enzymatic Reduction

2016

View full text Add to dashboard Cite

Enzymatic reduction using oxidoreductases is important in commercial chemical production. This enzymatic action requires a cofactor (e.g., NADH) as a hydrogen source that is consumed during reaction and must be regenerated. We present, for the first time, an in situ NADH regeneration (NAD + → NADH) using a heterogeneous catalyst (Pt/Al 2 O 3 ) and H 2 coupled with an enzymatic reduction. This regeneration system can be operated at ambient pressure where NADH yield and turnover frequency (TOF) increased with temperature (20−37 °C) and pH (4.0−9.9) delivering full selectivity to enzymatically active NADH. Cofactor regeneration by heterogeneous catalysis represents a cleaner (H + as sole byproduct) alternative to current enzymatic and homogeneous (electro-and photo-) catalytic methods with the added benefit of facile catalyst separation. The viability of coupling cofactor regeneration with enzymatic (alcohol dehydrogenase, ADH) reaction is established in aldehyde reduction (propanal to propanol) where 100% alcohol yield was achieved. The potential of this hybrid inorganic−enzymatic system is further demonstrated in the continuous (fed-batch) conversion of propanal with catalyst (activity/selectivity) stability for up to 100 h.

show abstract

Section: Introductionmentioning

confidence: 99%

Heterogeneous Catalysis Mediated Cofactor NADH Regeneration for Enzymatic Reduction

2016

View full text Add to dashboard Cite

show abstract

“…The questionable atom economy and also efficiency of such systems has triggered an interest in utilizing enzymes as biocatalysts for such transformations. Enzymes from several different classes are able to catalyze the two‐electron transfer from an alcohol to an acceptor and may therefore serve as candidate biocatalysts . The enzyme superfamily of alcohol dehydrogenases (ADHs) contains enzymes dependent on NAD(P) + or NAD(P)H, as an acceptor and donor, respectively, for hydride transfer reactions between alcohols and the cognate carbonyl compounds.…”

Section: Introductionmentioning

confidence: 99%

Relaxation of nonproductive binding and increased rate of coenzyme release in an alcohol dehydrogenase increases turnover with a nonpreferred alcohol enantiomer

et al. 2017

View full text Add to dashboard Cite

Alcohol dehydrogenase A (ADH-A) from Rhodococcus ruber DSM 44541 is a promising biocatalyst for redox transformations of arylsubstituted sec-alcohols and ketones. The enzyme is stereoselective in the oxidation of 1-phenylethanol with a 300-fold preference for the (S)-enantiomer. The low catalytic efficiency with (R)-1-phenylethanol has been attributed to nonproductive binding of this substrate at the active site. Aiming to modify the enantioselectivity, to rather favor the (R)-alcohol, and also test the possible involvement of nonproductive substrate binding as a mechanism in substrate discrimination, we performed directed laboratory evolution of ADH-A. Three targeted sites that contribute to the active-site cavity were exposed to saturation mutagenesis in a stepwise manner and the generated variants were selected for improved catalytic activity with (R)-1-phenylethanol. After three subsequent rounds of mutagenesis, selection and structure-function analysis of isolated ADH-A variants, we conclude: (1) W295 has a key role as a structural determinant in the discrimination between (R)-and (S)-1-phenylethanol and a W295A substitution fundamentally changes the stereoselectivity of the protein. One observable effect is a faster rate of NADH release, which changes the rate-limiting step of the catalytic cycle from coenzyme release to hydride transfer. (2) The obtained change in enantiopreference, from the (S)-to the (R)-alcohol, can be partly explained by a shift in the nonproductive substrate binding modes.

show abstract

“…Furthermore, the stoichiometric addition of an auxiliary molecule for cofactor regeneration is necessary, which severely reduces the atom economy of the process. 7 In a heterotrophic cell, the most common chassis for BVMOs, a considerable part of the nicotinamide cofactors are diverted toward respiration which, therefore, renders it as an additional oxygen sink. To this end, the use of photosynthetic cyanobacteria, which use photosynthetic water splitting for both oxygen evolution and the regeneration of redox cofactors, as hosts is advantageous 8 ( Scheme 1 ).…”

mentioning

confidence: 99%

Photobiocatalytic Oxyfunctionalization with High Reaction Rate using a Baeyer–Villiger Monooxygenase from Burkholderia xenovorans in Metabolically Engineered Cyanobacteria

et al. 2021

View full text Add to dashboard Cite

Baeyer–Villiger monooxygenases (BVMOs) catalyze the oxidation of ketones to lactones under very mild reaction conditions. This enzymatic route is hindered by the requirement of a stoichiometric supply of auxiliary substrates for cofactor recycling and difficulties with supplying the necessary oxygen. The recombinant production of BVMO in cyanobacteria allows the substitution of auxiliary organic cosubstrates with water as an electron donor and the utilization of oxygen generated by photosynthetic water splitting. Herein, we report the identification of a BVMO from Burkholderia xenovorans (BVMO Xeno ) that exhibits higher reaction rates in comparison to currently identified BVMOs. We report a 10-fold increase in specific activity in comparison to cyclohexanone monooxygenase (CHMO Acineto ) in Synechocystis sp. PCC 6803 (25 vs 2.3 U g DCW –1 at an optical density of OD 750 = 10) and an initial rate of 3.7 ± 0.2 mM h –1 . While the cells containing CHMO Acineto showed a considerable reduction of cyclohexanone to cyclohexanol, this unwanted side reaction was almost completely suppressed for BVMO Xeno , which was attributed to the much faster lactone formation and a 10-fold lower K M value of BVMO Xeno toward cyclohexanone. Furthermore, the whole-cell catalyst showed outstanding stereoselectivity. These results show that, despite the self-shading of the cells, high specific activities can be obtained at elevated cell densities and even further increased through manipulation of the photosynthetic electron transport chain (PETC). The obtained rates of up to 3.7 mM h –1 underline the usefulness of oxygenic cyanobacteria as a chassis for enzymatic oxidation reactions. The photosynthetic oxygen evolution can contribute to alleviating the highly problematic oxygen mass-transfer limitation of oxygen-dependent enzymatic processes.

show abstract

Biocatalytic Applications

Cited by 18 publications

References 1,606 publications

Heterogeneous Catalysis Mediated Cofactor NADH Regeneration for Enzymatic Reduction

Heterogeneous Catalysis Mediated Cofactor NADH Regeneration for Enzymatic Reduction

Relaxation of nonproductive binding and increased rate of coenzyme release in an alcohol dehydrogenase increases turnover with a nonpreferred alcohol enantiomer

Photobiocatalytic Oxyfunctionalization with High Reaction Rate using a Baeyer–Villiger Monooxygenase from Burkholderia xenovorans in Metabolically Engineered Cyanobacteria

Contact Info

Product

Resources

About