Exploring the substrate scope of Baeyer-Villiger monooxygenases with branched lactones as entry towards polyesters

Baeyer-Villiger monooxygenases (BVMOs) are biocatalysts able to convert cyclic ketones to lactones by the insertion of oxygen. The aim of this study was to explore the substrate scope of several BVMOs with (biobased) cyclic ketones as precursors for the synthesis of branched polyesters.The product structure and the degree of conversion of several biotransformations was determined after conversions using self-sufficient BVMOs. Full regioselectivity towards the normal lactone of jasmatone and menthone was observed, while the oxidation of other substrates such as α,β-thujone and 3,3,5-trimethylcyclohexanone resulted in mixtures of regio-isomers. This exploration of the substrate scope of both established as well as newly discovered BVMOs towards biobased ketones contributes to the development of branched polyesters from renewable resources

A Prospective Life Cycle Assessment (LCA) of Monomer Synthesis: Comparison of Biocatalytic and Oxidative Chemistry

Biotechnological processes are typically perceived to be greener than chemical processes. A life cycle assessment (LCA) was performed to compare the chemical and biochemical synthesis of lactones obtained by Baeyer-Villiger oxidation. The LCA is prospective (based on experiments at a small scale with primary data) because the process is at an early stage. The results show that the synthesis route has no significant effect on the climate change impact [(1.65 +/- 0.59)kgCO2 g(product)(-1) vs. (1.64 +/- 0.67)kgCO2 g(product)(-1)]. Key process performance metrics affecting the environmental impact were evaluated by performing a sensitivity analysis. Recycling of solvents and enzyme were shown to provide an advantage to the enzymatic synthesis. Additionally, the climate change impact was decreased by 71% if renewable electricity was used. The study shows that comparative LCAs can be used to usefully support decisions at an early stage of process development.</p

Towards High-performance Materials Based on Carbohydrate-Derived Polyamide Blends

A bio-derived monomer called 2,3:4,5-di-O-isopropylidene-galactarate acid/ester (GalXMe) has great potential in polymer production. The unique properties of this molecule, such as its rigidity and bulkiness, contribute to the good thermal properties and appealing transparency of the material. The main problem, however, is that like other biobased materials, the polymers derived thereof are very brittle. In this study, we report on the melt blending of GalXMe polyamides (PAs) with different commercial PA grades using extrusion as well as blend characterization. Biobased PA blends showed limited to no miscibility with other polyamides. However, their incorporation resulted in strong materials with high Young moduli. The increase in modulus of the prepared GalXMe blends with commercial PAs ranged from up to 75% for blends with aliphatic polyamide composed of 1,6-diaminohexane and 1,12-dodecanedioic acid PA(6,12) to up to 82% for blends with cycloaliphatic polyamide composed of 4,4&prime;-methylenebis(cyclohexylamine) and 1,12-dodecanedioic acid PA(PACM,12). Investigation into the mechanism of blending revealed that for some polyamides a transamidation reaction improved the blend compatibility. The thermal stability of the biobased PAs depended on which diamine was used. Polymers with aliphatic/aromatic or alicyclic diamines showed no degradation, whereas with fully aromatic diamines such as p-phenylenediamine, some degradation processes were observed under extrusion conditions (260/270 &deg;C)

Application of a thermostable Baeyer-Villiger monooxygenase for the synthesis of branched polyester precursors

BACKGROUNDIt is widely accepted that the poor thermostability of Baeyer‐Villiger monooxygenases limits their use as biocatalysts for applied biocatalysis in industrial applications. The goal of this study was to investigate the biocatalytic oxidation of 3,3,5‐trimethylcyclohexanone using a thermostable cyclohexanone monooxygenase from Thermocrispum municipale (TmCHMO) for the synthesis of branched ε‐caprolactone derivatives as building blocks for tuned polymeric backbones. In this multi‐enzymatic reaction, the thermostable cyclohexanone monooxygenase was fused to a phosphite dehydrogenase (PTDH) in order to ensure co‐factor regeneration.RESULTSUsing reaction engineering, the reaction rate and product formation of the regio‐isomeric branched lactones were improved and the use of co‐solvents and the initial substrate load were investigated. Substrate inhibition and poor product solubility were overcome using continuous substrate feeding regimes, as well as a biphasic reaction system with toluene as water‐immiscible organic solvent. A maximum volumetric productivity, or space‐time‐yield, of 1.20 g L‐1 h‐1 was achieved with continuous feeding of substrate using methanol as co‐solvent, while a maximum product concentration of 11.6 g L‐1 was achieved with toluene acting as a second phase and substrate reservoir.CONCLUSIONThese improvements in key process metrics therefore demonstrate progress towards the up‐scaled Baeyer‐Villiger monooxygenase‐biocatalyzed synthesis of the target building blocks for polymer application.<br/

Solvent-Free Method for the Copolymerization of Labile Sugar-Derived Building Blocks into Polyamides

This research focuses on the preparation of biobased copolyamides containing biacetalized galactaric acid (GalX), namely, 2,3:4,5-di-<i>O</i>-isopropylidene-galactaric acid (GalXMe) and 2,3:4,5-di-<i>O</i>-methylene-galactaric acid (GalXH), in bulk by melt polycondensation of salt monomers. In order to allow the incorporation of temperature-sensitive sugar-derived building blocks into copolyamides at temperatures below the degradation temperature of the monomers and below their melting temperatures, a clever selection of salt monomers is required, such that the sugar-derived salt monomer dissolves in the other salt monomers. The polymerization was investigated by temperature dependent FT-IR and optical microscopy. The structure of the obtained copolyamides was elucidated by NMR and matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) techniques. The positive outcome of this modified polycondensation method depends on the solubility of sugar-derived polyamide salts in polyamide salts of comonomers and the difference between their melting temperatures, however does not depend on the melting temperature of the used sugar-derived monomer. A variety of comonomers was screened in order to establish the underlying mechanisms of the process

The Forgotten Pyrazines:Exploring the Dakin-West Reaction

Pyrazines are an underreported class of N-heterocycles available from nitrogen-rich biomass presenting an interesting functional alternative for current aromatics. In this work, access to pyrazines obtained from amino acids by using the 90 year old Dakin-West reaction was explored. After a qualitative screening several functional proteinogenic amino acids proved good substrates for this reaction, which were successfully scaled to multigram scale synthesis of the corresponding intermediate alpha-acetamido ketones. Subsequently, the conditions towards pyrazine formation using delta-amino-levulinic acid were optimized, and these were employed to synthesize a relevant set of five functional dimethylpyrazines in high purity. These pyrazines can be considered a versatile toolbox of aromatic building blocks for a wide range of applications, such as in the synthesis of polymers or metal-organic frameworks

Evaluación estilos de aprendizaje en trabajo social

En el marco de las nuevas estrategias de aprendizaje que se desprenden de las directrices de Bolonia que persiguen una mejora del rendimiento, es clave y primordial poder evaluar todos los factores que favorecen el aprendizaje. En este trabajo presentamos una parte de la investigación realizada con alumnos de Grado de Trabajo Social centrada en el estudio de la relación entre el enfoque de aprendizaje, con la forma de regular su aprendizaje y el tipo de rendimiento. La primera parte del trabajo se ha realizado tomando como base el cuestionario CHAEA, de Alonso, Gallego y Honey (1994). Los resultados obtenidos nos permiten afirmar que existen diferencias estadísticas significativas en las puntuaciones de los cuatro estilos de aprendizaje entre los alumno

Toward Upscaled Biocatalytic Preparation of Lactone Building Blocks for Polymer Applications

Although Baeyer–Villiger monooxygenases (BVMOs) have gained attention in recent years, there are few cases of their upscaled application for lactone synthesis. A thermostable cyclohexanone monooxygenase from Thermocrispum municipale (TmCHMO) was applied to the oxidation of 3,3,5-trimethylcyclohexanone using a glucose dehydrogenase (GDH) for cofactor regeneration. The reaction progress was improved by optimizing the biocatalyst loading, with investigation into oxygen limitations. The product concentration and productivity were increased by keeping the substrate concentration below the inhibitory level via continuous substrate feeding (CSF). This substrate feeding strategy was evaluated against two biphasic reactions using either toluene or <i>n</i>-butyl acetate as immiscible organic solvents. A product concentration of 38 g L^–1 and a space-time yield of 1.35 g L^–1 h^–1 were achieved during the gram-scale synthesis of the two regioisomeric lactones by applying the CSF strategy. These improvements contribute to the large-scale application of BVMOs in the synthesis of branched building blocks for polymer applications