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Alcohol oxidation for the generation of carbonyl groups, is an essential reaction for the preparation of fine chemicals. Although a number of chemical procedures have been reported, biocatalysis is a promising alternative for more sustainable and selective processes. To speed up the discovery of novel (bio)catalysts for industrial applications, efficient screening approaches need to be established. Here, we report on an enzyme-mediated alcohol oxidation screening platform to rapidly detect the activities and selectivities of three classes of biocatalysts; ketoreductases (KREDs), alcohol oxidases (AlcOXs) and laccase-mediator systems (LMSs) with diverse substrates. [ABSTRACT FROM AUTHOR]

Alcohol dehydrogenases (ADH) are versatile and useful enzymes employed as biocatalysts, especially for the selective oxidation of primary and secondary alcohols, and for the reduction of carbonyl moieties. A new alcohol dehydrogenase (HeADH‐II) has been identified from the genome of the halo‐adapted bacterium Halomonas elongata, which proved stable in the presence of polar organic solvents and salt exposure. Unusual for this class of enzymes, HeADH‐II lacks enantiopreference and is capable of oxidizing both alcohols and aldehydes, enabling a direct overoxidation of primary alcohols to carboxylic acids. HeADH‐II was coupled with a NADH‐oxidase from Lactobacillus pentosus (LpNOX) to increase the process yields and allowing recycling of the cofactor. The enzymatic oxidation of primary alcohols was also paired with in situ condensation of the intermediate aldehydes with hydroxylamine to prepare the corresponding aldoximes, with particular attention to perillartine (a powerful sweetener), whose enzymatic synthesis starting from natural sources, leads to an equally natural product. [ABSTRACT FROM AUTHOR]

A new mild and efficient process for the aqueous preparation of aldehydes, which are employed as flavour and fragrance components in food, beverage, cosmetics, as well as in pharmaceuticals, was developed using a continuous-flow approach based on an immobilised pure transaminase-packed bed reactor. HEWT, an ω-transaminase from the haloadapted bacterium Halomonas elongata, has been selected for its excellent stability and substrate scope. Sixteen different amines were rapidly (3-15 min) oxidised to the corresponding aldehydes (90 to 99 %) with only 1 to 5 equivalents of sodium pyruvate. The process was fully automated, allowing for the in-line recovery of the pure aldehydes (chemical purity >99 % and isolated yields above 80 %), without any further work-up procedure. [ABSTRACT FROM AUTHOR]

A NADPH-dependent benzil reductase (KRED1-Pglu) was used as recombinant enzyme for catalysing the reduction of different functionalised ketones. The reactions were carried out in the presence of a catalytic amount of NADP + and an enzyme-coupled transformation (oxidation of glucose catalysed by glucose dehydrogenase), for regenerating the cofactor and thus driving the reaction to completion. KRED1-Pglu showed remarkable versatility, being able to reduce different β-ketonitriles and α-haloketones at different pHs; notably, depending on the nature of the substrate, KRED1-Pglu can be used for efficient and clean enzymatic reduction, avoiding side-reactions due to the pH of the medium. The reduction generally occurred with high enantioselectivity, allowing the preparation of enantiomerically enriched β-hydroxynitriles and halohydrins in high yields; the stereochemical outcome of the reduction followed in all the cases the so-called Prelog's rule. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of nature-inspired lipophilic phenolic esters was synthesized. • A biocatalyzed flow synthesis of phenolic esters in a green solvent was developed. • The optimized flow protocol included an efficient in-line purification procedure. • Novozyme 435® resulted highly stable in cyclopentyl methyl ether. • The amphiphilic phenolic esters were tested as antiradical and antimicrobial agents. A collection of nature-inspired lipophilic phenolic esters have been prepared by an enzymatic synthesis under flow conditions, using the immobilized lipase B from Candida antarctica (Novozyme 435®) as a catalyst in cyclopentyl methyl ether (CPME), a non-conventional and green solvent. Their antimicrobial activity against four selected bacterial strains together with their efficiency as radical scavengers were evaluated. The obtained compounds were characterized by enhanced lipophilicity in comparison with the parent non-esterified compounds, which increased the possibility of their use as additives in the food industry. [ABSTRACT FROM AUTHOR]

[Display omitted] A 2-step flow-based chemo-enzymatic synthesis of selected cinnamoyl tryptamines as potential cosmetic ingredients has been developed. A first reaction catalyzed by immobilized Pd(OAc) 2 gave the acyl donors employed as starting material in the second step, with very good yields (67–70%) and rapid reaction times (30 min). A second bioreactor made of imm-MsAcT, a glyoxyl-agarose immobilized acyl transferase from Mycobacterium smegmatis , was employed for the fast and efficient preparation of the desired amides (58–70% m.c., 15 min). In-line work-up allowing for the recovery and reuse of the unreacted substrates was added downstream the process, enhancing its automation. The combination of flow facilities, high substrate-to-catalyst ratio and closed-loop strategies make this methodology a sustainable and cost-effective procedure. Computational studies were carried out to provide insights into the enzymatic active site and substrate recognition [ABSTRACT FROM AUTHOR]

Enzyme immobilization has become a key strategy to improve the stability and recycling of biocatalysts, resulting in greener and more cost-efficient processes. The design of the immobilized catalysts is often focused only on the immobilization strategy, the binding chemistry between the enzyme and the support, while less attention has been paid to the physico-chemical properties of material supports. Selecting the best carrier for a specific application may greatly influence the performance of the biocatalytic reaction. Herein, we present a comparative study between the two most used material supports for protein immobilization, agarose and methacrylate. Hydrophilic agarose microbeads ensure higher retained enzymatic activity and better catalyst performance when hydrophobic compounds are involved in the biotransformation. Due to the high stickiness, lipophilic molecules represent a major limitation for methacrylate carriers. O2-dependent reactions, in contrast, must be carried out by immobilized enzymes on methacrylate supports due to the low mechanical stability of agarose under dehydration conditions. All these parameters were tested with a special focus on continuous-flow applications. [ABSTRACT FROM AUTHOR]

The Front Cover shows the ease of production of a range of aldehydes in continuous flow through an efficient enzymatic oxidation with minimal waste and in an environmentally friendly manner. In their Full Paper, M. L. Contente et al. demonstrate the use of an ω‐transaminase from Halomonas elongata as a heterogeneous biocatalyst in a mild and efficient single‐step process for the aqueous preparation of aldehydes in the presence of pyruvate, generating L‐alanine as a benign by‐product. More information can be found in the Full Paper by M. L. Contente et al. on page 3843 in Issue 20, 2017 (DOI: 10.1002/cctc.201701147). [ABSTRACT FROM AUTHOR]

The front cover artwork for Issue 20/2017 is a collaboration between the University of Nottingham (UK) and the University of Milan (Italy). The image shows the ease of production of a range of aldehydes in continuous flow through an efficient enzymatic oxidation with minimal waste and in an environmentally friendly manner. See the Full Paper itself at . [ABSTRACT FROM AUTHOR]

Various types of ketone substrates can be efficiently reduced in the presence of the title enzyme, isolated from P. [ABSTRACT FROM AUTHOR]

Optimized recombinant whole cells of E. coli bearing CYP153A6 were employed for catalyzing the hydroxylation of different monoterpene derivatives. In most cases, high selectivity was observed with exclusive hydroxylation of the allylic methyl group bound to the aliphatic ring. In the case of (R)- and (S)-carvone, hydroxylation occurred also on the other allylic methyl group, although to a lesser extent. Biotransformations carried out in fed-batch mode on (S)-limonene and α-terpineol showed that recombinant whole cells retained activity for at least 24 h, allowing for the recovery of 3.25 mg mL−1 of (S)-perillyl alcohol and 5.45 mg mL−1 of 7-hydroxy-α-terpineol, respectively. Keypoints: Different monoterpenes can be regioselectively hydroxylated by CYP153A6 monooxygenase The biotransformation with whole cells is complementary to chemical oxyfunctionalization Fed-batch biotransformations have been applied for preparative purposes [ABSTRACT FROM AUTHOR]

Saffron (Crocus sativus L.) spice, traditionally used as food additive for its coloring and flavoring properties, has shown great potential to promote health. Among the main constituents of saffron spice, safranal has been shown to alleviate and prevent gastric disorders, cardiovascular diseases and to exert anticonvulsant, anxiolytic, antidepressive and neuroprotective activities. In this work, we recovered picrocrocin from saffron residues and efficiently biotransformed it using a halo-thermophilic β-glucosidase from Alicyclobacillus acidophilus (Aac), which gave the corresponding aglycone 4-hydroxysafranal with complete conversion (>99%) and rapid reaction times (15 min). After a thermic treatment, safranal was obtained in excellent yields. To make the process even more efficient and sustainable a one-pot, 2-step chemo-enzymatic transformation was set up, yielding a marketable natural safranal as final product. [ABSTRACT FROM AUTHOR]

Microbial carboxylesterases are important biocatalysts that selectively hydrolyze an extensive range of esters. Here, we report the biochemical and structural characterization of an atypical carboxylesterase from Bacillus coagulans (BCE), endowed with high enantioselectivity toward different 1,2‐O‐isopropylideneglycerol (IPG or solketal) esters. BCE efficiently catalyzes the production of enantiopure (S)‐IPG, a chiral building block for the synthesis of β‐blockers, glycerophospholipids, and prostaglandins; efficient hydrolysis was observed up to 65 °C. To gain insight into the mechanistic bases of such enantioselectivity, we solved the crystal structures of BCE in apo‐ and glycerol‐bound forms at resolutions of 1.9 and 1.8 Å, respectively. In silico docking studies on the BCE structure confirmed that IPG esters with small acyl chains (≤ C6) were easily accommodated in the active site pocket, indicating that small conformational changes are necessary to accept longer substrates. Furthermore, docking studies suggested that enantioselectivity may be due to an improved stabilization of the tetrahedral reaction intermediate for the S‐enantiomer. Contrary to the above functional data implying nonlipolytic functions, BCE displays a lipase‐like 3D structure that hosts a “lid” domain capping the main entrance to the active site. In lipases the lid mediates catalysis through interfacial activation, a process that we did not observe for BCE. Overall, we present the functional‐structural properties of an atypical carboxyl esterase that has nonlipase‐like functions, yet possesses a lipase‐like 3D fold. Our data provide original enzymatic information in view of BCE applications as an inexpensive, efficient biocatalyst for the production of enantiopure (S)‐IPG. Database: Coordinates and structure factors have been deposited in the Protein Data Bank ( www.rcsb.org) under accession numbers 5O7G (apo‐BCE) and 5OLU (glycerol‐bound BCE) [ABSTRACT FROM AUTHOR]

The large consumption of freshwater in fermentations and bio-transformations is a matter of concern for the sustainability of many bio-processes. The use of seawater to perform bio-processes is a sustainable alternative. In this work, we used marine yeasts from deep-sub-seafloor sediments grown in seawater as bio-catalysts to perform the stereoselective reduction of different ketones, and the bio-transformations were accomplished in seawater as well. Strains of Meyerozyma guilliermondii and Rhodotorula mucilaginosa were able to reduce different aromatic ketones with high molar conversions and moderate-to-high enantioselectivity with no significant differences between bio-catalysis performed in seawater and freshwater. Finally, the selected marine yeasts were used for the reduction of key intermediates in seawater for the synthesis of molecules of pharmaceutical interest (desogestrel, norgestrel, gestodene, pramipexole). [ABSTRACT FROM AUTHOR]

Production of fructooligosaccharides (FOS) from sucrose was obtained using a bioprocess entirely performed in seawater. The halophilic fungus Cladosporium cladosporioides MUT 5506 was grown in a seawater-based medium and mycelium displayed an optimal activity in seawater at 50–60 °C, being stable up to 60 °C. Under optimized conditions in seawater (50 °C, sucrose 600 g/L, lyophilized mycelium 40 g/L), C. cladosporioides gave a maximum FOS yield of 344 g/L after 72 h with a preponderance of 1 F-FOS derivatives (1-kestose 184 g/L, 1-nystose 98 g/L and 1-fructofuranosylnystose 22 g/L), and the noteworthy presence of the non-conventional disaccharide blastose (30 g/L after 144 h). Lyophilized mycelium exhibited good stability in seawater (76% of the initial activity was retained after 15 cycles of reutilization). This proof-of-concept application reports for the first time the production of FOS in a non-conventional medium such as seawater. [ABSTRACT FROM AUTHOR]