NADH Recycling Research Articles

Formate Dehydrogenase: Recent Developments for NADH and NADPH Recycling in Biocatalysis

AbstractFormate dehydrogenases (FDHs) catalyze the oxidation of formate to CO2 while reducing NAD(P)+ to NAD(P)H and are classified into two main classes: metal‐dependent (Mo‐ or W‐containing) and metal‐independent FDHs. The latter are oxygen‐tolerant and relevant as a cofactor regeneration system for various bioprocesses and gained more and more attention due to their ability to catalyze the reverse CO2 reduction. This review gives an overview of metal‐independent FDHs, the recent advances made in this field, and their relevance for future applications in biocatalysis. This includes the exploitation of novel FDHs which have altered co‐substrate specificity as well as enzyme engineering approaches to improve process stability and general performance.

Mitochondrial complex I promotes kidney cancer metastasis.

Most kidney cancers are metabolically dysfunctional1-4, but how this dysfunction affects cancer progression in humans is unknown. We infused 13C-labelled nutrients in over 80 patients with kidney cancer during surgical tumour resection. Labelling from [U-13C]glucose varies across subtypes, indicating that the kidney environment alone cannot account for all tumour metabolic reprogramming. Compared with the adjacent kidney, clear cell renal cell carcinomas (ccRCCs) display suppressed labelling of tricarboxylic acid (TCA) cycle intermediates in vivo and in ex vivo organotypic cultures, indicating that suppressed labelling is tissue intrinsic. [1,2-13C]acetate and [U-13C]glutamine infusionsin patients, coupled with measurements of respiration in isolated human kidney and tumour mitochondria, reveal lower electron transport chain activity in ccRCCs that contributes to decreased oxidative and enhanced reductive TCA cycle labelling. However, ccRCC metastases unexpectedly have enhanced TCA cycle labelling compared with that ofprimary ccRCCs, indicating a divergent metabolic program during metastasis in patients. In mice, stimulating respiration or NADH recycling in kidney cancer cells is sufficient to promote metastasis, whereas inhibiting electron transport chain complex I decreases metastasis. These findings in humans and mice indicate that metabolic properties and liabilities evolve during kidney cancer progression, and that mitochondrial function is limiting for metastasis but not growth at the original site.

Mechanoresponsive Protein Crystals for NADH Recycling in Multicycle Enzyme Reactions.

NAD(H)-dependent enzymes play a crucial role in the biosynthesis of pharmaceuticals and fine chemicals, but the limited recyclability of the NAD(H) cofactor hinders its more general application. Here, we report the generation of mechano-responsive PEI-modified Cry3Aa protein crystals and their use for NADH recycling over multiple reaction cycles. For demonstration of its practical utility, a complementary Cry3Aa protein particle containing genetically encoded and co-immobilized formate dehydrogenase for NADH regeneration and leucine dehydrogenase for catalyzing the NADH-dependent l-tert-leucine (l-tert-Leu) biosynthesis has been produced. When combined with the PEI-modified Cry3Aa crystal, the resultant reaction system could be used for the efficient biosynthesis of l-tert-Leu for up to 21 days with a 10.5-fold improvement in the NADH turnover number.

Controlled Biocatalytic Synthesis of a Metal Nanoparticle‐Enzyme Hybrid: Demonstration for Catalytic H2‐driven NADH Recycling

AbstractHere we demonstrate the preparation of enzyme‐metal biohybrids of NAD+ reductase with biocatalytically‐synthesised small gold nanoparticles (NPs, <10 nm) and core‐shell gold‐platinum NPs for tandem catalysis. Despite the variety of methods available for NP synthesis, there remains a need for more sustainable strategies which also give precise control over the shape and size of the metal NPs for applications in catalysis, biomedical devices, and electronics. We demonstrate facile biosynthesis of spherical, highly uniform, gold NPs under mild conditions using an isolated enzyme moiety, an NAD+ reductase, to reduce metal salts while oxidising a nicotinamide‐containing cofactor. By subsequently introducing platinum salts, we show that core‐shell Au@Pt NPs can then be formed. Catalytic function of these enzyme‐Au@Pt NP hybrids was demonstrated for H2‐driven NADH recycling to support enantioselective ketone reduction by an NADH‐dependent alcohol dehydrogenase.

Controlled Biocatalytic Synthesis of a Metal Nanoparticle-Enzyme Hybrid: Demonstration for Catalytic H2-driven NADH Recycling.

Here we demonstrate the preparation of enzyme-metal biohybrids of NAD+ reductase with biocatalytically-synthesised small gold nanoparticles (NPs, <10 nm) and core-shell gold-platinum NPs for tandem catalysis. Despite the variety of methods available for NP synthesis, there remains a need for more sustainable strategies which also give precise control over the shape and size of the metal NPs for applications in catalysis, biomedical devices, and electronics. We demonstrate facile biosynthesis of spherical, highly uniform, gold NPs under mild conditions using an isolated enzyme moiety, an NAD+ reductase, to reduce metal salts while oxidising a nicotinamide-containing cofactor. By subsequently introducing platinum salts, we show that core-shell Au@Pt NPs can then be formed. Catalytic function of these enzyme-Au@Pt NP hybrids was demonstrated for H2-driven NADH recycling to support enantioselective ketone reduction by an NADH-dependent alcohol dehydrogenase.

Scalable Bioreactor Production of an O2‐Protected [FeFe]‐Hydrogenase Enables Simple Aerobic Handling for Clean Chemical Synthesis

AbstractThe enzyme CbA5H, a [FeFe]‐hydrogenase from Clostridium beijerinckii, has previously been shown to survive exposure to oxygen, making it a promising candidate for biotechnological applications. Thus far [NiFe]‐hydrogenases are typically considered for such applications, due to the superior O2‐tolerance and therefore simplified enzyme handling. However, methods for production of [FeFe]‐hydrogenases are generally more successful than for other classes of hydrogenases, therefore in this work we focus on demonstrating scalable CbA5H production, and report results with active enzyme prepared in bioreactors (up to 10 L) with &gt;20‐fold improvement in purified enzyme yield. We then go on to confirm excellent H2/H+‐cycling activity of the air‐purified protein, highlighting that CbA5H can be prepared and isolated without the need for complex and expensive infrastructure. Next, we demonstrate good stability of the air‐purified CbA5H both in solution assays, and as a heterogenous catalyst system when immobilized on a carbon support. Finally, we successfully implement this enzyme within previously demonstrated biotechnologies for flavin and NADH recycling, highlighting its relevance in chemical synthesis, and we demonstrate production of an important API precursor, 3‐quinuclidinol at &gt;0.4 g scale in standard benchtop hydrogenation infrastructure, with &gt;100,000 CbA5H turnovers over 18 operational hours.

Construction novel yeast surface-displaying glucose-leucine dehydrogenase fusions for cofactor recycling and chiral amino acid biosynthesis

Whole-cell biosynthesis of chiral amino acids (AAs) is of significant potential application. However, the difficulty of reactant translocation cell membranes limits their industrial utilization. In this study, a fusion enzyme integrating glucose dehydrogenase and leucine dehydrogenase (BmGDH-L-EsLDH) was engineered and anchored on the yeast surface, thereby enhancing cofactor recycling and catalytic efficiency of chiral AA production. In order to optimize the expression, a strategy of codon optimization was implemented. The surface-displayed opt-BmGDH-L-EsLDH reached to 2380 U/g (wet cell weight), which was 1.8-fold higher than the control. Moreover, the fusion enzyme markedly improved temperature and pH tolerance compared to the single enzyme. The NADH recycling efficiency of the fusion enzyme was augmented by 8-fold compared to the individual enzyme. The production of L-tert-leucine reached 2710 g/L/d in 200 mL scale without the addition of external NADH, achieving a total turnover number (TTN) of 9960 for NADH recycling. The surface-displayed BmGDH-L-EsLDH fusion demonstrated robust performance in biosynthesis of chiral amino acids.

Tungsten Enzyme Using Hydrogen as an Electron Donor to Reduce Carboxylic Acids and NAD.

Tungsten-dependent aldehyde oxidoreductases (AORs) catalyze the oxidation of aldehydes to acids and are the only known enzymes reducing non-activated acids using electron donors with low redox potentials. We report here that AOR from Aromatoleum aromaticum (AORAa) catalyzes the reduction of organic acids not only with low-potential Eu(II) or Ti(III) complexes but also with H2 as an electron donor. Additionally, AORAa catalyzes the H2-dependent reduction of NAD+ or benzyl viologen. The rate of H2-dependent NAD+ reduction equals to 10% of that of aldehyde oxidation, representing the highest H2 turnover rate observed among the Mo/W enzymes. As AORAa simultaneously catalyzes the reduction of acids and NAD+, we designed a cascade reaction utilizing a NAD(P)H-dependent alcohol dehydrogenase to reduce organic acids to the corresponding alcohols with H2 as the only reductant. The newly discovered W-hydrogenase side activity of AORAa may find applications in either NADH recycling or conversion of carboxylic acids to more useful biochemicals.

The seed biochemical signature as a potent marker for water logging tolerance in maize

Plant breeders are in the need for convenient, reproducible, reliable and rapid screening methods to be used as a proxy for water logging tolerance for a large number of genotypes. Addressing this need, the present study was carried in order to identify potential biochemical markers in the seeds of 10 contrasting maize (Zea mays L.) genotypes differing in their tolerance against water logging. Results clearly indicate that tolerant genotypes inherently exhibit better antioxidant system as evident by higher activities of catalase and glutathione reductase than the susceptible genotypes hence minimizes resulting oxidative stress. Significantly higher activities of anaerobic metabolism enzymes viz. alcohol dehydrogenase, aldehyde dehydrogenase and pyruvate decarboxylase in tolerant maize genotypes signifies efficient system for the recycling of NADH for the continuation of glycolysis and simultaneous detoxification of acetaldehyde thus provides prolonged survival of tolerant plants under water logging. Higher Sucrose synthase (SuSy) activity in tolerant genotypes over the susceptible genotypes indicates uninterrupted supply of reducing sugars for glycolytic activity. The content of total and reducing sugars content was found 27% higher in tolerant genotypes, which is in agreement with the SuSy activity. Soluble sugars analysis through reverse phase HPLC revealed higher relative concentration of fructose and glucose in tolerant maize genotypes than susceptible genotypes. Tolerant genotypes also exhibited significantly lower phytic acid and higher proline content. Hence the observed biochemical diversity could be useful for screening and development of water logging stress-tolerant genotypes of maize.

One-carbon metabolism in cancer cells: a critical review based on a core model of central metabolism.

One-carbon metabolism (1C-metabolism), also called folate metabolism because the carbon group is attached to folate-derived tetrahydrofolate, is crucial in metabolism. It is at the heart of several essential syntheses, particularly those of purine and thymidylate. After a short reminder of the organization of 1C-metabolism, I list its salient features as reported in the literature. Then, using flux balance analysis, a core model of central metabolism and the flux constraints for an 'average cancer cell metabolism', I explore the fundamentals underlying 1C-metabolism and its relationships with the rest of metabolism. Some unreported properties of 1C-metabolism emerge, such as its potential roles in mitochondrial NADH exchange with cytosolic NADPH, participation in NADH recycling, and optimization of cell proliferation.

Production of Ethylene Glycol from Glycerol Using an In Vitro Enzymatic Cascade

Glycerol is a readily available and inexpensive substance that is mostly generated during biofuel production processes. In order to ensure the viability of the biofuel industry, it is essential to develop complementing technologies for the resource utilization of glycerol. Ethylene glycol is a two-carbon organic chemical with multiple applications and a huge market. In this study, an artificial enzymatic cascade comprised alditol oxidase, catalase, glyoxylate/hydroxypyruvate reductase, pyruvate decarboxylase and lactaldehyde:propanediol oxidoreductase was developed for the production of ethylene glycol from glycerol. The reduced nicotinamide adenine dinucleotide (NADH) generated during the dehydrogenation of the glycerol oxidation product d-glycerate can be as the reductant to support the ethylene glycol production. Using this in vitro synthetic system with self-sufficient NADH recycling, 7.64 ± 0.15 mM ethylene glycol was produced from 10 mM glycerol in 10 h, with a high yield of 0.515 ± 0.1 g/g. The in vitro enzymatic cascade is not only a promising alternative for the generation of ethylene glycol but also a successful example of the value-added utilization of glycerol.

Berberine affects mitochondrial activity and cell growth of leukemic cells from chronic lymphocytic leukemia patients

B-cell chronic lymphocytic leukemia (CLL) results from accumulation of leukemic cells that are subject to iterative re-activation cycles and clonal expansion in lymphoid tissues. The effects of the well-tolerated alkaloid Berberine (BRB), used for treating metabolic disorders, were studied on ex-vivo leukemic cells activated in vitro by microenvironment stimuli. BRB decreased expression of survival/proliferation-associated molecules (e.g. Mcl-1/Bcl-xL) and inhibited stimulation-induced cell cycle entry, irrespective of TP53 alterations or chromosomal abnormalities. CLL cells rely on oxidative phosphorylation for their bioenergetics, particularly during the activation process. In this context, BRB triggered mitochondrial dysfunction and aberrant cellular energetic metabolism. Decreased ATP production and NADH recycling, associated with mitochondrial uncoupling, were not compensated by increased lactic fermentation. Antioxidant defenses were affected and could not correct the altered intracellular redox homeostasis. The data thus indicated that the cytotoxic/cytostatic action of BRB at 10–30 μM might be mediated, at least in part, by BRB-induced impairment of oxidative phosphorylation and the associated increment of oxidative damage, with consequent inhibition of cell activation and eventual cell death. Bioenergetics and cell survival were instead unaffected in normal B lymphocytes at the same BRB concentrations. Interestingly, BRB lowered the apoptotic threshold of ABT-199/Venetoclax, a promising BH3-mimetic whose cytotoxic activity is counteracted by high Mcl-1/Bcl-xL expression and increased mitochondrial oxidative phosphorylation. Our results indicate that, while CLL cells are in the process of building their survival and cycling armamentarium, the presence of BRB affects this process.

Electroenzymatic NADH Recycling for Selective in-Flow Biocatalytic Reductions

Demand for greater environmental and economic sustainability in organic syntheses is driven by the chemical industry’s desire to reduce energy consumption, eliminate undesirable side products and develop more efficient reactions. There is growing interest in electrosynthesis for organic redox reactions, utilizing electrodes as a very clean electron source or sink,[1] but it is currently underrepresented in organic synthesis due to a range of limitations, particularly with selectivity and difficulties in implementation. Currently 10-20% of industrial transformations are catalytic hydrogenations, often using noble-metals.[2] These catalysts frequently require high pressures of hydrogen and can suffer from poor chemo- and enantio-selectivity. This study demonstrates bioelectrocatalysis for selective C=X bond reductions, offering an alternative to traditional hydrogenations. Biocatalysts such as oxidoreductase enzymes offer exquisite selectivity under mild reaction conditions, but have proved difficult to exploit in electrosynthesis. These enzymes often require stoichiometric hydride transfer from the expensive biological NAD(P)H cofactor, which means that their use is only viable when they are coupled with an efficient cofactor recycling method. Glucose or isopropanol in super-stoichiometric quantities are often used to recycle the reduced cofactor, NADH, but this approach suffers from poor atom economy. Electrochemically-driven regeneration of the NADH cofactor is problematic at unfunctionalized electrodes due to formation of non-active forms of the reduced cofactor. Here, we present an electrochemically-driven NADH regeneration system with NAD+-reductase modified carbon electrodes, offering perfect selectivity for the active NADH cofactor. We show that we can immobilize this enzyme onto carbon interfaces and that it is electrochemically active at much more modest potentials than using unmodified electrodes.[3] We demonstrate this recycling system as a modular approach to biocatalytic reductions,[4,5] coupling NADH-dependent reductases onto the same carbon interface for efficient C=X reductions (Figure 1). Application of this bioelectrocatalytic interface to an electrochemical flow cell increases catalytic activity further and we observe that this interface is stable over many days of continuous use.

Enhancing cofactor recycling in the bioconversion of racemic alcohols to chiral amines with alcohol dehydrogenase and amine dehydrogenase by coupling cells and cell-free system.

Alcohol dehydrogenase (ADH) and amine dehydrogenase (AmDH)-catalyzed one-pot cascade conversion of an alcohol to an amine provides a simple preparation of chiral amines. To enhance the cofactor recycling in this reaction, we report a new concept of coupling whole-cells with the cell-free system to enable separated intracellular and extracellular cofactor regeneration and recycling. This was demonstrated by the respective biotransformation of racemic 4-phenyl-2-butanol 1a and 1-phenyl-2-propanol 1b to (R)-4-phenylbutan-2-amine 3a and (R)-1-phenylpropan-2-amine 3b. Escherichia coli cells expressing S-enantioselective CpsADH, R-enantioselective PfODH, and NADH oxidase (NOX) was developed to oxidize racemic alcohols 1a-b to ketones 2a-b with full conversion via intracellular NAD+ recycling. AmDH and glucose dehydrogenase (GDH) were used to convert ketones 2a-b to amines (R)-3a-b with 89-94% conversion and 891-943 times recycling of NADH. Combining the cells and enzymes for the cascade transformation of racemic alcohols 1a-b gave 70% and 48% conversion to the amines (R)-3a and (R)-3b in 99% ee, with atotal turnover number (TTN) of 350 and 240 for NADH recycling, respectively. Improved results were obtained by using the E. coli cells with immobilized AmDH and GDH: (R)-3a was produced in 99% ee with 71-84% conversion and a TTN of 1410-1260 for NADH recycling, the highest value so far for the ADH-AmDH-catalyzed cascade conversion of alcohols to amines. The concept might be generally applicable to this type of reactions.

Production of value-added chemicals from glycerol using in vitro enzymatic cascades

The large surplus of glycerol derived from the expanding biofuel industry raises economic and environmental concerns regarding disposal. In vitro synthetic biology is emerging as a useful biomanufacturing platform while the conversion of glycerol is rarely investigated. Here we develop a thermostable in vitro synthetic biosystem consisting of three enzymatic cascades for the biotransformation of glycerol into valuable chemicals with different degrees of reduction. Condensation of glycerol, phenol, and ammonium into l-tyrosine is achieved using four enzymes without the assistance of NAD+/NADH-related redox reactions. Production of chemicals with high degrees of reduction (e.g., optically pure l-lactate and d-lactate) is also verified through coupling with an NADH-regeneration system. The biotransformation of glycerol and ammonium into l-serine is achieved using four enzymes with self-sufficient NADH recycling.

Coupled Immobilized Amine Dehydrogenase and Glucose Dehydrogenase for Asymmetric Synthesis of Amines by Reductive Amination with Cofactor Recycling

AbstractThe amine dehydrogenase (AmDH) engineered from the phenylalanine dehydrogenase of Rhodococcus sp. M4 was directly immobilized on magnetic nanoparticles (MNP) from the cell‐free extract containing his‐tagged AmDH through affinity attachment to give AmDH‐MNPs with high yield, enzyme loading efficiency, and specific enzyme loading. AmDH‐MNPs showed higher activity and productivity than the free enzyme for the asymmetric reductive amination of 4‐phenyl‐2‐butanone 1 a and phenylacetone 1 b, producing the corresponding amines (R)‐2 a,b in 99 % ee and 99 % yield, and with recycling of NADH for up to 3956 times. AmDH‐MNPs were easily recycled, retaining 91 % of the original productivity in the third cycle of the reductive amination of 1 a. Coupling of immobilized AmDH and immobilized glucose dehydrogenase (GDH) for the asymmetric reductive amination of 1 a gave (R)‐2 a in 99 % ee and 74 % yield, with a total turnover number (TTN) of 2940 for NADH recycling. Both immobilized enzymes showed good recyclability, retaining 81 % productivity in the third reaction cycle. The developed method with coupled immobilized AmDH and immobilized GDH for the asymmetric reductive amination of ketones is useful for the synthesis of enantiopure amines, superior to the use of coupled isolated enzymes with enhanced catalytic performance and reduced enzyme cost through catalyst recycling.

Redox Balance in Lactobacillus reuteri DSM20016: Roles of Iron-Dependent Alcohol Dehydrogenases in Glucose/ Glycerol Metabolism

Lactobacillus reuteri, a heterofermentative bacterium, metabolizes glycerol via a Pdu (propanediol-utilization) pathway involving dehydration to 3-hydroxypropionaldehyde (3-HPA) followed by reduction to 1,3-propandiol (1,3-PDO) with concomitant generation of an oxidized cofactor, NAD+ that is utilized to maintain cofactor balance required for glucose metabolism and even for oxidation of 3-HPA by a Pdu oxidative branch to 3-hydroxypropionic acid (3-HP). The Pdu pathway is operative inside Pdu microcompartment that encapsulates different enzymes and cofactors involved in metabolizing glycerol or 1,2-propanediol, and protects the cells from the toxic effect of the aldehyde intermediate. Since L. reuteri excretes high amounts of 3-HPA outside the microcompartment, the organism is likely to have alternative alcohol dehydrogenase(s) in the cytoplasm for transformation of the aldehyde. In this study, diversity of alcohol dehydrogenases in Lactobacillus species was investigated with a focus on L. reuteri. Nine ADH enzymes were found in L. reuteri DSM20016, out of which 3 (PduQ, ADH6 and ADH7) belong to the group of iron-dependent enzymes that are known to transform aldehydes/ketones to alcohols. L. reuteri mutants were generated in which the three ADHs were deleted individually. The lagging growth phenotype of these deletion mutants revealed that limited NAD+/NADH recycling could be restricting their growth in the absence of ADHs. Notably, it was demonstrated that PduQ is more active in generating NAD+ during glycerol metabolism within the microcompartment by resting cells, while ADH7 functions to balance NAD+/NADH by converting 3-HPA to 1,3-PDO outside the microcompartment in the growing cells. Moreover, evaluation of ADH6 deletion mutant showed strong decrease in ethanol level, supporting the role of this bifuctional alcohol/aldehyde dehydrogenase in ethanol production. To the best of our knowledge, this is the first report revealing both internal and external recycling for cofactor homeostasis during 3-HPA conversion in L. reuteri.

Selection of an endogenous 2,3-butanediol pathway in Escherichia coli by fermentative redox balance

Fermentative redox balance has long been utilized as a metabolic evolution platform to improve efficiency of NADH-dependent pathways. However, such system relies on the complete recycling of NADH and may become limited when the target pathway results in excess NADH stoichiometrically. In this study, endogenous capability of Escherichia coli for 2,3-butanediol (2,3-BD) synthesis was explored using the anaerobic selection platform based on redox balance. To address the issue of NADH excess associated with the 2,3-BD pathway, we devised a substrate-decoupled system where a pathway intermediate is externally supplied in addition to the carbon source to decouple NADH recycling ratio from the intrinsic pathway stoichiometry. In this case, feeding of the 2,3-BD precursor acetoin effectively restored anaerobic growth of the mixed-acid fermentation mutant that remained otherwise inhibited even in the presence of a functional 2,3-BD pathway. Using established 2,3-BD dehydrogenases as model enzyme, we verified that the redox-based selection system is responsive to NADPH-dependent reactions but with lower sensitivity. Based on this substrate-decoupled selection scheme, we successfully identified the glycerol/1,2-propanediol dehydrogenase (Ec-GldA) as the major enzyme responsible for the acetoin reducing activity (kcat/Km≈0.4mM−1s−1) observed in E. coli. Significant shift of 2,3-BD configuration upon withdrawal of the heterologous acetolactate decarboxylase revealed that the endogenous synthesis of acetoin occurs via diacetyl. Among the predicted diacetyl reductase in E. coli, Ec-UcpA displayed the most significant activity towards diacetyl reduction into acetoin (Vmax≈6U/mg). The final strain demonstrated a meso-2,3-BD production titer of 3g/L without introduction of foreign genes. The substrate-decoupled selection system allows redox balance regardless of the pathway stoichiometry thus enables segmented optimization of different reductive pathways through enzyme bioprospecting and metabolic evolution.

Biosynthesis of optically pure chiral alcohols by a substrate coupled and biphasic system with a short-chain dehydrogenase from Streptomyces griseus.

The increasing demand for biocatalysts in synthesizing enantiomerically pure chiral alcohols results from the outstanding characteristics of enzymes in reaction, economic, ecological issues. Many carbonyl reductases for producing chiral alcohols have been reported but there is still a lack of good catalytic efficacies. Herein, five carbonyl reductases from different Streptomyces were discovered by the strategy of genome mining. These reductases were overexpressed, and we chose SgCR for further study as it owned better enzyme activity. This protein was purified to apparent homogeneity, and its amino acid sequence was analyzed in comparison with that of the reported SDRs. The biocatalytic properties of SgCR were investigated, and this enzyme was confirmed to have the ability to convert various prochiral ketones into highly optically active alcohols. SgCR exhibited the highest activity towards ethyl 4-chloro-3-oxobutanoate (COBE) and the corresponding product ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE) was obtained with high yield and excellent e.e. value by optimizing the biphasic system. Eventually, using isopropanol as the co-substrate for NADH recycling in the substrate-coupled reaction, the yield and enantioselectivity of (S)-CHBE were obtained at the values of 90% and 99%, respectively. These results indicate that SgCR is a promising boicatalyst for the synthesis of chiral alcohols in industry.

Inside Back Cover: Enzyme‐Modified Particles for Selective Biocatalytic Hydrogenation by Hydrogen‐Driven NADH Recycling (ChemCatChem 21/2015)

The Cover shows a new approach to biocatalysis involving enzymes on carbon particles as a heterogeneous catalyst for H2-driven hydrogenations. In their Full Paper, Reeve et al. demonstrate that these particles operate in unbuffered water, give high yields of phenylethanol from acetophenone, and are easy to separate and re-use. Reaction rate is enhanced by co-immobilizing NADH-dependent alcohol dehydrogenase with the H2-driven NADH recycling system, and high turnover numbers of both enzyme and cofactor are achieved. More details can be found in the Full Paper by K. A. Vincent et al. on page 3480 in Issue 21, 2015 (DOI: 10.1002/cctc.201500766).