A chemo-enzymatic approach for the conversion of oleic acid into azelaic and pelargonic acid is herein described. It represents a sustainable alternative to ozonolysis, currently employed at the industrial scale to perform the reaction. Azelaic acid is produced in high chemical purity in 44% isolation yield after three steps, avoiding column chromatography purifications. In the first step, the lipase-mediated generation of peroleic acid in the presence of 35% H2O2 is employed for the self-epoxidation of the unsaturated acid to the corresponding oxirane derivative. This intermediate is submitted to in situ acid-catalyzed opening, to afford 9,10-dihydroxystearic acid, which readily crystallizes from the reaction medium. The chemical oxidation of the diol derivative, using atmospheric oxygen as a stoichiometric oxidant with catalytic quantities of Fe(NO3)3∙9∙H2O, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), and NaCl, affords 9,10-dioxostearic acid which is cleaved by the action of 35% H2O2 in mild conditions, without requiring any catalyst, to give pelargonic and azelaic acid.

Ene-reductases from the Old Yellow Enzyme (OYE) superfamily are a well-known and efficient biocatalytic alternative for the asymmetric reduction of C=C bonds. Considering the broad variety of substituents that can be tolerated, and the excellent stereoselectivities achieved, it is apparent why these enzymes are so appealing for preparative and industrial applications. Different classes of C=C bonds activated by at least one electron-withdrawing group have been shown to be accepted by these versatile biocatalysts in the last decades, affording a vast range of chiral intermediates employed in the synthesis of pharmaceuticals, agrochemicals, flavours, fragrances and fine chemicals. In order to access both enantiomers of reduced products, stereodivergent pairs of OYEs are desirable, but their natural occurrence is limited. The detailed knowledge of the stereochemical course of the reaction can uncover alternative strategies to orient the selectivity via mutagenesis, evolution, and substrate engineering. An overview of the ongoing studies on OYE-mediated bioreductions will be provided, with particular focus on stereochemical investigations by deuterium labelling.

The conversion of C5 and C6 cycloalkenecarboxylates into both enantiomers of the corresponding cyclic γ-oxoesters is performed at room temperature using three enzymes and no environmentally-unfriendly oxidants.

The review will discuss the methods that have been optimized so far for the enzymatic hydrolysis of soapstock into enriched mixtures of free fatty acids, in order to offer a sustainable alternative to the procedure which is currently employed at the industrial level for converting soapstock into the by-product known as acid oil (or olein, i.e., free fatty acids removed from raw vegetable oil, dissolved in residual triglycerides). The further biocatalyzed manipulation of soapstock or of the corresponding acid oil for the production of biodiesel and fine chemicals (surfactants, plasticizers, and additives) will be described, with specific attention given to processes performed in continuous flow mode. The valorization of soapstock as carbon source in industrial lipase production will be also considered.

Enantiomerically enriched 2-hydroxymethylalkanoic acids were prepared by oxidative desymmetrisation of achiral 1,3-diols using immobilized cells of Acetobacter aceti in water at 28 °C. The biotransformations were first performed in batch mode with cells immobilized in dry alginate, furnishing the desired products with high molar conversion and reaction times ranging from 2 to 6 h. The biocatalytic process was intensified using a multiphasic flow reactor, where a segmented gas–liquid flow regime was applied for achieving an efficient O2-liquid transfer; the continuous flow systems allowed for high yields and high biocatalyst productivity.

Ene-reductases (ERs) belonging to the old yellow enzyme (OYE) family have been thoroughly investigated for the stereospecific reduction of activated prochiral C=C double bonds. In this work, OYE3 was immobilized both by covalent binding on glyoxyl-agarose (OYE3-GA), and by affinity-based adsorption on EziGTM particles (OYE3-EziG). The immobilized OYE3-GA was demonstrated to be active (activity recovery = 52%) and to retain almost 100% of its activity under the enzymatic assay conditions (50 mM phosphate buffer pH 7, 28 °C) for six days, whereas the activity of the non-immobilized enzyme dropped to 50% after two days. In the case of EziGTM, the highest activity recovery (54%) was achieved by using the most hydrophilic carrier (EziGTM Opal) that was selected for the full characterization of this type of enzyme preparation (stability, recycling, re-use, enzyme leakage). OYE3-EziG was slightly less stable than OYE3-GA under the same experimental conditions. OYE3-GA could be recycled and re-used for up to 12 reaction cycles in the bioreduction of α-methyl-trans-cinnamaldehyde; after 12 runs, the highest conversion achieved was 40%. In the case of the co-immobilized OYE3/GDH-EziG, the conversion dropped to 56% after two reaction cycles. No enzyme leakage was detected over 48 h for both OYE3-GA and OYE3/GDH-EziG (50 mM phosphate buffer pH 7, 28 °C). These seed results pave the way for a true optimization of the immobilization of OYE3, as well as for the use of immobilized OYE3 for preparative applications both in batch and continuous flow conditions.

Soapstock recovery and manipulation represent one of the most burdensome aspects of the vegetable seed oil refining industry. In particular, soapstock splitting requires high amounts of concentrated acid and produces...

The chemoselective hydrogenation of alkenes in the presence of alkynes is a very challenging transformation to achieve with traditional chemical methods. The development of an effective procedure to perform this transformation would enrich the tool-kit available to organic chemists for the development of useful synthetic routes, and the creation of novel structural motifs. The reduction of activated alkene bonds by ene-reductases (ERs) is completely chemoselective, because of the mechanism of the reaction. Thus, we investigated the use of ERs belonging to the Old Yellow Enzyme family for the reduction of α,β-unsaturated aldehydes with a conjugated C�C triple bond at the γ position. This reaction was exploited as the key step for the development of an effective homologation route to convert aryl and alkyl substituted propynals and butynones into 4-alkynals and 4-alkynols, avoiding some troublesome or hazardous steps of known synthetic routes. Scheme 4. Conversion of aldehydes (R)-8 a, b and alcohols (S)-10 a, b into derivatives of known absolute configuration.