Limonene Oxide Research Articles

Reinforcement of bio‐based network polymer with wine pomace

AbstractPolymer materials prepared using renewable resources such as agricultural and food wastes would lead to a sustainable society. Our target was a synthesis of fiber‐reinforced network polymer derived from citrus oil and wine pomace. Lignocellulose nanofiber (LCNF) was successfully prepared from wine pomace by mechanical fibrillation using disk mill grinder under wet condition, followed by freeze‐drying. The resultant LCNF with coarse powder‐like (the untreated LCNF) enabled to reinforce bio‐based network polymer derived from limonene oxide even though heterogeneously dispersed LCNF was observed in the polymer matrix. Polymer/LCNF composite material with almost homogeneously dispersed LCNF was obtained using LCNF prepared from alcohol‐exchange process prior to freeze‐drying (the alcohol‐exchanged LCNF). Tensile strength of the network polymer reinforced by 2% of alcohol‐exchanged LCNF was around 3.2 times higher than that of the polymer without any LCNF. Dynamic mechanical analysis measurement exhibited that cross‐link density of the network polymer reinforced by 2% of alcohol‐exchanged LCNF was around 1.4 times higher than that of the neat polymer. It is noted that the cross‐linker for bio‐based network polymer, branched polyethyleneimine, likely acted as a dispersing agent for LCNF.

Hydroformylation and one-pot hydroformylation/epoxy ring cleavage of limonene oxide: A sustainable access to biomass-based multi-functional fragrances

Naturally occurring, renewable limonene oxide is converted into aldehydes with pleasant scent under oxo (hydroformylation) conditions. Good activity and selectivity are only reached by the careful choice of the catalytic system and the reaction conditions. [Rh(COD)(OMe)]2 was used as the catalyst precursor and PPh3 or (2,4-di-tBuC6H3O)3P as auxiliary ligands, the latter showing better results. The process can be carried in eco-friendly solvents such as anisole, ethanol, dimethylcarbonate (DMC) and diethylcarbonate (DEC). Employing Rh/(2,4-di-tBuC6H3O)3P catalytic system and acetic anhydride or acetic acid as co-reactants, a concomitant one-pot epoxide opening takes place along with hydroformylation, resulting in new acetylated aldehydes potentially useful for the fragrance industry. With the former co-reactant diacetylated products are preferred, while with the latter co-reactant hydroxy acetoxy aldehydes are formed in high yields. The one pot hydroformylation/epoxy ring cleavage process can be also performed in green solvents: DMC, DEC and anisole.

Viable route and DFT study for the synthesis of optically active limonaketone: A barely available natural feedstock in Cedrus atlantica

Herein, we report a novel, easy and efficient synthesis pathway of optically active limonaketone, a high added value monoterpene, starting from limonene, natural and low-cost feedstock. The strategy was developed in an excellent three-step total synthesis of limonaketone, potentially important intermediate in limonene ozonolysis and barely available in Cedrus atlantica essential oil (0.1% yield). The first step was the epoxidation of limonene which proceed in 91% yield. The ozonolysis of the prepared limonene oxide leads to the formation of the characteristic ketone function of limonaketone in 92% yield. The last step was performed by a deoxygenation in the presence of Zn and gave limonaketone in quantitative yield. The optically pure limonaketone has been efficiently synthesized from limonene and the overall yield was 84%. A molecular electron density theory (MEDT) analysis was carried out by using density functional theory (DFT) calculations at the M06–2X/6–311G(d,p) (LANL2DZ for Zn) level to understand the observed chemoselectivity in the Zn-deoxygenation reaction as well as its corresponding mechanistic pathway.

Antimicrobial activity of bioactive components of essential oils from Citrus sinensis against important pathogens

Alternative strategies to treat multidrug resistant pathogens are indispensable due to the scarcity of new therapeutically effective antibiotics. The present work was conducted to investigate the antimicrobial effects of essential oils extracted from Citrus sinensis, locally known as “Mousami”, against various important pathogens as well as their phytochemical characterisation. Essential oils were extracted from Cit. sinensis peels by the steam distillation method, and a 0.23% yield was obtained. Chemical composition of the extracted essential oil was analysed through gas chromatography/mass spectrometry (GC/MS). The analysis revealed that the Cit. sinensis essential oil was composed of a variety of chemical compounds; mostly are monoterpene hydrocarbon and 0.62% of limonene (dipentene), as well as oxygenated monoterpenes and 0.50% limonene oxide, also known as eucalyptol. Standard reference microorganisms, i.e., E. coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Salmonella Typhi (ATCC 24682), Bacillus subtilis (ATCC 6633), Aspergillus flavus (ATCC 204304), and Candida albicans (ATCC 10231) were used, and the in vitro antimicrobial effect of Cit. sinensis essential oils was observed against these strains by disc diffusion method. Statistical analysis of the resulting data was done by using Least Significant Difference (LSD) method and Analysis of Variance (ANOVA) to assess the significant association between biological activities of essential oils at p < 0.05. Using microbroth dilution assay, maximum sensitivity was exhibited by E. coli and Can. albicans among the tested microbial strains. The zones of inhibition were significantly different, having diameters of 34.0 ± 1.5 and 55.0 ± 0.5 mm for the said bacterial and fungal strains, respectively; and their MIC values were 0.0007 ± 0.0001 and 0.0007 ± 0.0006 mg/ml, respectively. Thin layer chromatography-bioautography (TLC-bioautography) showed dipentene as biologically most active antimicrobial component. Hence, it was established that broad spectrum antimicrobial effect against important microorganisms was elucidated by essential oil extracts from Cit. sinensis that may be used as a natural antimicrobial to treat various infections caused by pathogens of public health interest.

Unimolecular Reactions Following Indoor and Outdoor Limonene Ozonolysis.

Limonene is one of the monoterpenes with the largest biogenic emissions and is also widely used as an additive in cleaning products, leading to significant indoor emissions. Studies have found that the formation of secondary organic aerosols (SOAs) from limonene oxidation has important implications for indoor air quality. Although ozonolysis is considered the major limonene oxidation pathway under most indoor conditions, little is known about the mechanisms for SOA formation from limonene ozonolysis. Here, we calculate the rate coefficients of the possible unimolecular reactions of the first-generation peroxy radicals formed by limonene ozonolysis using a high-level multiconformer transition state theory approach. We find that all of the peroxy radicals formed initially in the ozonolysis of limonene react unimolecularly with rates that are competitive both indoors and outdoors, except under highly polluted conditions. Differences in reactivity between the peroxy radicals from ozonolysis and those formed by OH, NO3, and Cl oxidation are discussed. Finally, we sketch possible oxidation mechanisms for the different peroxy radicals under both indoor and pristine atmospheric conditions and in more polluted environments. In environments with low concentrations of HO2 and NO, efficient autoxidation will lead to the formation of highly oxygenated organic compounds and thus likely aid in the growth of SOA.

Kinetic Separation of cis-and trans-Limonene Epoxide: Reaction of Diastereomeric Mixture of Limonene Oxides with Secondary Amine and Carbamate

A simple kinetic separation of (1:1) diastereomeric mixture of limonene oxides was used to purify cis-and trans-diastereomers of (R)-(+)-limonene oxide. The epoxide ring of trans-isomer was selectively opened by (R)-N-methyl-(α-methyl-benzyl)amine. This secondary nucleophilic amine left cis-limonene oxide largely unreacted and was obtained up to 90% yield. In a diverse way, (R)-N-(α-methylbenzyl) ethyl carbamate, selectively catalyze hydrolysis of cis-limonene oxide to 1,2-limonene diol leaving trans-limonene oxide largely unreacted. The unreacted trans-limonene oxide was recovered in up to 75% yield. HPLC and NMR analyses were used to demonstrate that the isolation of cis-and trans-diastereomers of (R)-(+)-limonene oxide has shown that > 98% were pure. As a result, depending on the realization of the secondary amine or carbamate in the presence of water, either cis-or trans-limonene oxide may be obtained in high diastereomeric purity.

Synthesis of bio-based poly limonene oxide with green catalyst

In the present work, the polymerization of limonene oxide (LO) catalyzed by Maghnite H+ (Mag- H+) is investigated. Mag-H+ is Algerian montmorillonite sheet silicate clay exchanged with protons. The poly limonene oxide (PLO) is obtained by cationic ring opening polymerization in bulk and with solvent. The effect of the reaction time, the temperature and the amount of catalyst are studied and discussed in order to find the optimal reactions conditions. The polymerization in solution at 0 °C with 5% by weight of catalyst leads to the best yield 61.34% for a reaction time of 1h. The structure of the obtained products is characterized by XRD, 1H-NMR, 13C-RMN, ATR-FTIR, DSC and TGA.

α-Pinene, Limonene, and Cyclohexene Secondary Organic Aerosol Hygroscopicity and Oxidation Level as a Function of Volatility

ABSTRACT The hygroscopicity and oxidation level of secondary organic aerosol (SOA) produced in an atmospheric simulation chamber were measured as a function of volatility. The experimental setup combines thermodenuding, isothermal dilution, aerosol mass spectroscopy, and size-resolved cloud condensation nuclei measurements to separate the SOA by volatility and then measure its physical (hygroscopicity via the hygroscopicity parameter, κ) and chemical (oxidation level via the oxygen-to-carbon ratio, O:C) properties. The technique was applied to SOA from the ozonolysis of α-pinene, limonene, and cyclohexene. The O:C and κ of the α-pinene ozonolysis SOA decreased as volatility decreased. The semi-volatile and the low volatility organic compounds produced during limonene ozonolysis have similar O:C and κ values, but the corresponding extremely low volatility organic compounds have significantly lower oxygen content and hygroscopicity. The average O:C of the cyclohexene ozonolysis SOA increased, but the average κ decreased as volatility decreased. These results suggest that some organic aerosol (OA) systems have a more complex relationship between hygroscopicity, oxidation level, and volatility than originally thought. The two-dimensional volatility basis set framework can help in integrating these results and providing explanations of the measured hygroscopicity. Use of this technique with different OA systems, both laboratory and ambient, can supply parameters that can be incorporated in atmospheric chemical transport models.

Limonene-derived polycarbonates as biobased UV-curable (powder) coating resins

The evaluation of poly(limonene carbonate)s (PLCs), derived from orange oils and carbon dioxide, as UV-curable (powder) coating binders is described. PLCs with moderate molecular weight were prepared by copolymerization of limonene oxide with CO2 and a subsequent molecular weight reduction step by transcarbonation with 1,10-decanediol (1,10-DCD). These PLCs were cured with a trifunctional thiol monomer in the presence of a photoinitiator via thiol-ene chemistry to form poly(thioether-co-carbonate) networks. The UV curing of the resins following solvent casting was studied at 130 °C using ATR-FTIR, revealing a fast curing and a quick thiol-ene network (TEN) formation, realized by the addition reactions of thiol groups of the curing agent onto pendant isopropenyl groups of PLC. An ene addition enhanced by thiol-ene crosslinking was also observed, known as a ‘cage effect’, which was discovered for the first time in a UV-curable thiol-ene system. The efficient TEN formation was also evidenced by the high sol fractions in those UV-cured samples and their dynamic mechanical thermal analysis (DMTA). The DMTA results of these TENs showed high Tgs (up to 125.9 °C) and a wide range of thermomechanical properties, including rubbery moduli from 4.4–27.5 MPa. The UV-cured powder coating employing PLCs as binders showed outstanding properties such as high transparency, good acetone resistance, high pencil hardness (H-2 H) and high König hardness (174−199 s), suggesting their potential as very promising biobased alternatives to conventional powder coating resins.

Catalytic performance of V-MCM-41 nanocomposites in liquid phase limonene oxidation: Vanadium leaching mitigation

Chemical stability and catalytic performance of MCM-41 materials functionalized with vanadium by template-ion exchange (TIE) were studied. Solids with different vanadium loadings were synthesized and characterized by a multi-technique approach. Their textural and chemical properties were analyzed by low and high angle XRD, N 2 adsorption-desorption, SEM, UV–vis DR, XPS, FTIR-Py and ICP-OES. All solids exhibited a highly ordered mesoporous structure, characteristic of MCM-41 materials. Their specific areas, pore diameters and pore volumes were found to be suitable for application as catalysts in liquid phase oxidation reactions. From different tests of limonene oxidation with H 2 O 2 , it was found that isolated cations (V δ+ ) are more likely to be the active sites for this reaction. Additionally, results show that high vanadium content actually lowers catalytic performance and favors sub-product formation by secondary reactions. Recycling tests were performed using the lowest vanadium content sample, finding that considerable leaching of active species took place after two reactions cycles. Wet impregnation with titanium was tested as a strategy for vanadium leaching mitigation. Solids with different titanium loadings were synthesized and evaluated. One of the bimetallic materials was selected according to its enhanced catalytic activity which accounts for an interesting synergistic effect between vanadium and titanium. This solid also displayed a superior chemical stability, since the absence of leaching was successfully proven in successive reaction cycles. • V-MCM-41 solids were successfully synthesized by TIE and extensively characterized. • Solids with different V loading were tested in limonene oxidation with H 2 O 2 . • The lowest V content solid exhibited the best catalytic performance. • Significant leaching of V species was detected after successive reaction cycles. • Ti impregnation is featured as an attractive strategy for V leaching mitigation.

Incubation with a Complex Orange Essential Oil Leads to Evolved Mutants with Increased Resistance and Tolerance.

Emergence of strains with increased resistance/tolerance to natural antimicrobials was evidenced after cyclic exposure to carvacrol, citral, and (+)-limonene oxide. However, no previous studies have reported the development of resistance and tolerance to complex essential oils (EOs). This study seeks to evaluate the occurrence of Staphylococcus aureus strains resistant and tolerant to a complex orange essential oil (OEO) after prolonged cyclic treatments at low concentrations. Phenotypic characterization of evolved strains revealed an increase of minimum inhibitory and bactericidal concentration for OEO, a better growth fitness in presence of OEO, and an enhanced survival to lethal treatments, compared to wild-type strain. However, no significant differences (p > 0.05) in cross-resistance to antibiotics were observed. Mutations in hepT and accA in evolved strains highlight the important role of oxidative stress in the cell response to OEO, as well as the relevance of the cell membrane in the cell response to these natural antimicrobials. This study demonstrates the emergence of S. aureus strains that are resistant and tolerant to EO (Citrus sinensis). This phenomenon should be taken into account to assure the efficacy of natural antimicrobials in the design of food preservation strategies, in cleaning and disinfection protocols, and in clinical applications against resistant bacteria.

Bio-based polyether from limonene oxide catalytic ROP as green polymeric plasticizer for PLA

In this work, the polymerization of Limonene Oxide (LO) has been achieved using an Earth abundant metal-based catalyst developed in our group, that is very active in ring opening polymerization (ROP) processes. The bio-based polylimonene ether (PLO) obtained had low molecular weight and good thermal properties, thus being a potential green polymeric additive for other bio-based polymers such as PLA. Hence, we have explored its ability to influence PLA properties. The addition of only 10 wt %, led to the modification and improvement of PLA properties in terms of flexibility, thermal stability, and hydrophobicity. The results obtained are promising and open up the potential industrial application of PLO for the melt-processing of blends based on PLA/PLO. These new materials are totally based on renewable sources and may be interesting for many applications where biodegradability and reduced water adsorption is required, such as food packaging or agricultural mulch films.

Chemoenzymatic Epoxidation of Limonene Using a Novel Surface-Functionalized Silica Catalyst Derived from Agricultural Waste.

Limonene is one of the most important terpenes having wide applications in food and fragrance industries. The epoxide of limonene, limonene oxide, finds important applications as a versatile synthetic intermediate in the chemical industry. Therefore, attempts have been made to synthesize limonene oxide using eco-friendly processes because of stringent regulations on its production. In this regard, we have attempted to synthesize it using a cost-effective and eco-friendly process. Chemoenzymatic epoxidation of limonene to limonene oxide was carried out using in situ generation of peroxy octanoic acid from octanoic acid and H2O2. In this study, agricultural-waste rice husk ash (RHA)-derived silica was surface-functionalized using (3-aminopropyl) triethoxysilane (APTS), which was cross-linked using glutaraldehyde for immobilization of Candida antarctica lipase B. Furthermore, the immobilized enzyme was entrapped in calcium alginate beads to avoid enzyme leaching. Thus, limonene oxide was prepared using this catalyst under conventional and microwave heating. The microwave irradiation intensifies the process, reducing the reaction time under the same conditions. Maximum conversion of limonene to limonene oxide of 75.35 ± 0.98% was obtained in 2 h at 50 °C using a microwave power of 50 W. In the absence of microwave irradiation, the conventional heating gave 44.6 ± 1.14% conversion in 12 h. The reaction mechanism was studied using the Lineweaver–Burk plot, which follows a ternary complex mechanism with inhibition due to peroxyoctanoic acid (in other words H2O2). The prepared catalyst shows high reusability and operational stability up to four cycles.

NNC-Scorpionate Zirconium-Based Bicomponent Systems for the Efficient CO2 Fixation into a Variety of Cyclic Carbonates.

Two new derivatives of the bis(3,5-dimethylpyrazol-1-yl)methane modified by introduction of organosilyl groups on the central carbon atom, one of which bearing a chiral fragment, have been easily prepared. We verified the potential utility of these compounds through the reaction with [Zr(NMe2)4] for the preparation of novel zirconium complexes in which an ancillary bis(pyrazol-1-yl)methanide acts as a robust monoanionic tridentate scorpionate in a κ3-NNC chelating mode, forming strained four-membered heterometallacycles. These κ3-NNC-scorpionate zirconium amides were investigated as catalysts in combination with tetra-n-butylammonium bromide as cocatalyst for CO2 fixation into five-membered cyclic carbonate products. The study has led to the development of an efficient zirconium-based bicomponent system for the selective cycloaddition reaction of CO2 with epoxides. Kinetics investigations confirmed apparent first-order dependence on the catalyst and cocatalyst concentrations. In addition, this system displays very broad substrate scope, including mono- and disubstituted substrates, as well as the challenging biorenewable terpene derived limonene oxide, under mild and solvent-free conditions.

Aliphatic polycarbonates derived from epoxides and CO2: A comparative study of poly(cyclohexene carbonate) and poly(limonene carbonate)

The ring-opening copolymerization (ROCOP) of epoxides and CO2 provides an alternative approach towards polycarbonates and due to their aliphatic nature, they represent an interesting alternative to bisphenol-A based polycarbonates. A Lewis acidic β-diiminate (BDI)CF3-Zn-(SiMe3)2 complex 1 is used in the ROCOP of CO2 with cyclohexene oxide (CHO) and limonene oxide (LO), respectively. The knowledge gained from polymerizations monitored via in situ IR spectroscopy was used to upscale the reactions to a 1 L reactor. The two products poly(cyclohexene carbonate) (PCHC) and poly(limonene carbonate) (PLC) were then characterized via thermal analysis, a multiaxial pressure test, and dynamic mechanical analysis and compared with commercial polymers. While PCHC and PLC were both thermally stable at 150 °C for 20 min and only minor decomposition occurred at 180 °C, PLC is prone to cross-linking at elevated temperatures. This could be prevented by hydrogenation of the double bond or by the addition of an antioxidant. In the mechanical performance, the aliphatic polymers ranged between the highly impact resistant Durabio® and the brittle PMMA but broke without a splintering of the material. Overall, this study enabled a classification of CO2-based polycarbonates, especially of the novel PLC. Additionally, complex 1 was active in the terpolymerization of CHO, LO, and CO2. The formation of an actual terpolymer was confirmed via aliquot gel-permeation chromatography and diffusion-ordered NMR spectroscopy. High-pressure NMR techniques reveal an interesting kinetic feature. CHO gets copolymerized with CO2 exclusively, and LO incorporation only starts when CHO is fully consumed.

Diastereoselective Synthesis of P-Stereogenic Secondary Phosphine Oxides (SPOs) Bearing a Chiral Substituent by Ring Opening of (+)-Limonene Oxide with Primary Phosphido Nucleophiles.

Kinetic separation of the commercially available cis/trans-(+)-limonene oxide mixture by ring opening with primary phosphido nucleophiles LiPHR (R = ferrocenyl, Ph, Cy, t-Bu, Mes* (Mes* = 2,4,6-(t-Bu)3C6H2)), followed by treatment with aqueous NH4Cl and H2O2, gave unreacted cis-(+)-limonene oxide and diastereoenriched mixtures of the secondary phosphine oxides (SPOs) PHR(trans-(+)-Lim-OH)(O), which could be separated by chromatography and/or recrystallization. This one-pot synthesis uses a cheap chiral material and commercially available primary phosphines to control the configuration of the new P-stereogenic SPOs, which are potentially useful as ligands for metal complexes in asymmetric catalysis.

Sustainable catalytic rearrangement of terpene-derived epoxides: towards bio-based biscarbonyl monomers.

Seeking a sustainable and selective approach for terpene modification, a catalyst deconvolution approach was applied to the Meinwald rearrangement of (+)-limonene oxide as a model substrate to yield dihydrocarvone. In order to identify the most suitable catalyst and reaction conditions, different Lewis acids were evaluated. Bismuth triflate proved to be the most active catalyst under mild reaction conditions, with a low catalyst loading (1 mol%) and a relatively short reaction time (3 h). The optimized reaction conditions were subsequently transferred to other terpene-based epoxides, yielding different bio-based biscarbonyl structures, which constitute interesting and valuable substances, e.g. for polymer synthesis or as fragrances. Monoepoxides derived from (R)-(-)-carvone and (+)-dihydrocarvone rearranged to the desired products with high selectivities and yields. γ-Terpinene dioxide could be transformed in a double rearrangement to the respective biscarbonyl in moderate yields. A better result was achieved for limonene dioxide after further adjustment of the protocol to reach acceptable yields with a low catalyst loading of 0.1 mol% using 2-methyl tetrahydrofuran as a sustainable solvent. Compared to many procedures described in the literature, this procedure represents a step towards an increased sustainability in terpene modification by considering several principles of Green Chemistry, such as renewable resources, catalysis and mild reaction conditions for elementary chemical transformations. This article is part of a discussion meeting issue 'Science to enable the circular economy'.

Low‐Viscosity Limonene Dimethacrylate as a Bio‐Based Alternative to Bisphenol A‐Based Acrylic Monomers for Photocurable Thermosets and 3D Printing

AbstractBisphenol A glycidyl methacrylate (BisGMA) is well established as photocurable resin in dental restoratives and 3D printing. At present there are raising concerns regarding the estrogen‐mimicking bisphenol A (BPA) contamination of health care and consumer products. It is an important challenge to substitute BPA‐based resins for bio‐based cycloaliphatic monomers while lowering resin viscosity without sacrificing high stiffness and glass temperature. Particularly high viscosity is critical for 3D printing by photopolymerization. Unlike BPA the cyclic monoterpene limonene, extracted from citrus fruit peels, is safe in human uses. Herein it is reported on limonene‐based dimethacrylate (LDMA) tailored for 3D printing application and derived from limonene oxide (LO) and methacrylic acid (MA). Residual MA is converted into glycerol dimethacrylate (GDMA) serving as an in situ reactive diluent. The influences of temperature, catalysts, MA/LO stoichiometry, and the addition of glycidyl methacrylate (GMA) and magnesium oxide on the LDMA‐based resin performance are elucidated. As compared to BisGMA (560 Pa s) LDMA‐based resins exhibit significantly lower viscosity (5–117 Pa s) governed by the MA/LDMA molar ratio and the GMA addition. At 30 wt% LDMA content photocured resin yields thermosets having high Young’s Modulus (3.4–3.7 GPa), tensile strength (88–98 MPa), and glass transition temperature (119–135 °C), surpassing the performance of the corresponding BisGMA‐based resins.

Identification and catalytic properties of new epoxide hydrolases from the genomic data of soil bacteria

Epoxide hydrolases (EHs) catalyse the conversion of epoxides into vicinal diols. These enzymes have extensive value in biocatalysis as they can generate enantiopure epoxides and diols which are important and versatile synthetic intermediates for the fine chemical and pharmaceutical industries. Despite these benefits, they have seen limited use in the bioindustry and novel EHs continue to be reported in the literature.We identified twenty-nine putative EHs within the genomes of soil bacteria. Eight of these EHs were explored in terms of their activity. Two limonene epoxide hydrolases (LEHs) and one ⍺/β EH were active on a model compound styrene oxide and its ring-substituted derivatives, with low to good percentage conversions of 18–86%. Further exploration of the substrate scope with enantiopure (R)-styrene oxide and (S)-styrene oxide, showed different epoxide ring opening regioselectivities. Two enzymes, expressed from plasmids pQR1984 and pQR1990 de-symmetrised the meso-epoxide cyclohexene oxide, forming the (R,R)-diol with high enantioselectivity. Two LEHs, from plasmids pQR1980 and pQR1982 catalysed the hydrolysis of (+) and (−) limonene oxide, with diastereomeric preference for the (1S,2S,4R)- and (1R,2R,4S)-diol products, respectively. The enzyme from plasmid pQR1982 had a good substrate scope for a LEH, being active towards styrene oxide, its analogues, cyclohexene oxide and 1,2-epoxyhexane in addition to (±)-limonene oxide.The enzymes from plasmids pQR1982 and pQR1984 had good substrate scopes and their enzymatic properties were characterised with respect to styrene oxide. They had comparable temperature optima and pQR1984 had 70% activity in the presence of 40% of the green solvent MeOH, a useful property for bio-industrial applications. Overall, this study has provided novel EHs with potential value in industrial biocatalysis.

A comprehensive methodology based on NTME/GC-MS data and chemometric tools for lemons discrimination according to geographical origin

In this work we report an innovative and high throughput methodology involving Needle Trap Microextraction (NTME) combined with GC-MS analyis and chemometric processing, to obtain comprehensive volatile fingerprints for authenticity purposes. This approach ewill allow to characterize the volatile composition of lemon peels (exocarp) (Eureka variety) from different geographical regions of Portugal (mainland and Madeira Island), Argentine and South Africa as useful tool to identify geographic molecular markers with potential for discrimination according to their geographical origin. The most important parameters affecting NTME, namely extraction and headspace volumes, sample temperature and equilibration time, were optimized using an experimental design (DoE). Overall, 75 volatile organic compounds (VOCs), belonging to different chemical groups, namely monoterpenes, sesquiterpenes, alcohols and carbonyl compounds, were identified. D-limonene, α-pinene, β-pinene, sabinene, β-myrcene and γ-terpinene were the dominant volatiles identified, accounting for more than 50% of the volatile composition of selected lemons varieties. The VOCs data matrix obtained was submitted to both supervised (Orthogonal Projections to Latent Structures Discriminant Analysis, OPLS-DA) and unsupervised (Hierarchical Clustering Analysis, HCA) statistics, allowing to discriminate lemons based on the volatomic fingerprint of its peel. The VOCs with the larger contribution to the geographical origin classification included butanal, α-pinene, α-thujene, 1-butanol, 2-heptanone, D-limonene, 2-methyl-2-heptenal, nonanal, decanal, 1-octanol, limonene oxide, β-caryophyllene and 2,6-dimethyl-2,6-octadiene, suggesting their potential as geographical markers. This study shows the potential of NTMS/GC-MS combined with multivariate statistical analysis as a powerful and rapid strategy to obtain volatile fingerprints of different food matrices and support the certification of their origin and authenticity.