1,720,991 research outputs found
Enzymatic route for selective glycerol oxidation using covalently immobilized laccases
No full textGlycerol is an important starting material for the synthesis of many chemical compounds and its selective oxidation represents an efficient way to produce value-added compounds. Glyceric acid, one of these selective oxidation products, is an important intermediate in the food, medicine, cosmetics, and light industries. In this work, four commercially available native laccases were screened for glycerol oxidation using different initiators,and the two most efficient biocatalysts were covalently immobilized on functionalized magnetic and polymethacrylate (LifetechTM) solid supports. Apart from the mostly employed Fe3O4 magnetic particles, in this work Ni-Zn or Ni-Zn-Co spinel ferrite (MFe2O4) microparticles were used. Particularly, the utilization (for the first time for laccase immobilization) of Ni-Zn ferrite support Ni0.7Zn0.3Fe2O4 functionalized with 3-aminopropyl-trimethoxysilane, via crosslinking by glutaraldehyde and reduction with NaBH4 led to excellent biocatalytic efficiency and stability. These results confirm the feasibility of Trametes versicolor laccase for covalent bonding, as presumed by computational modelling. The resulted enzymatic preparations were characterized in detail in terms of stability and reusability, demonstrating enhanced storage, pH and thermal stability compared to the native enzymes. The most active biocatalysts (790.93 [U/g]) were successfully used for glycerol oxidation and the specific conversion in glyceric acid exceeded 50
Bis-pyrrolidone structures as versatile building blocks for the synthesis of bio-based polyesters and for the preparation of additives
No full textIn this work, three bis-pyrrolidone-based structures (BP) were synthesized combining dimethyl itaconate (DMI), the dimethyl ester derivative of itaconic acid, with various aliphatic diamines having a C4 to C12 carbon chain length with the aim of developing novel bio-based building blocks. All three BPs were obtained with a purity >93% and could further be used without performing any tedious purification step, therefore allowing an easy scalability of the synthesis on a 10 g scale. Their potential application was demonstrated in two key areas of modern polymer science: (1) the enzymatic synthesis of polyesters and (2) their use as poly(lactic acid) (PLA) additives. Firstly, the possibility of obtaining oligoesters by reacting the BP monomers with various aliphatic diols in a solventless reaction system and under mild conditions (T < 90 °C) was demonstrated thanks to the use of enzymatic catalysis. Linear oligoesters having mean average molecular weights between 1000 g mol−1 and 6100 g mol−1 and dispersity values <2 were successfully obtained. When applying the BP structures as PLA additives, the incorporation of a 10% w w−1 BP in the polyester matrix resulted in systems with an 8× increased elongation at break and a decrease in the glass transition temperature compared to the neat polymer matrix
Turning biomass into functional composite materials: rice husk for fully renewable immobilized biocatalysts
Full text linkRice husk is an underexploited, low density and highly robust composite material, massively available from rice processing. Here we report two new procedures for the formulation of immobilized lipases applicable in fats and oils transformations. The enzymes were covalently anchored on aldehyde groups introduced on rice husk by laccase-catalysed oxidation of the cellulose component. The method avoids the use of toxic glutaraldehyde while allows for the application and recycling of the biocatalysts in aqueous media. The second method used a fluidized bed granulator for the coating of the particles of rice husk (200–400 m) in the presence of water-soluble binders. The formulations are mechanically stable and suitable for applications in different hydrophobic media. Both methods allow for the recovery and reuse of the rice husk at the end of the life cycle of the biocatalysts
Integrating Computational and Experimental Methods for the Rational Ecodesign and Synthesis of Functionalized Safe and Sustainable Biobased Oligoesters
Full text linkA chemical platform for post-polymerization methods was developed, starting from the ecodesign and enzymatic synthesis of safe and sustainable bio-based polyesters containing discrete units of itaconic acid. This unsaturated bio-based monomer enables the covalent linkage of molecules that can impart desired properties such as hydrophilicity, flexibility, permeability, or affinity for biological targets. Molecular descriptor-based computational methods, which are generally used for modeling the pharmacokinetic properties of drugs (ADME), were employed to predict in silico the hydrophobicity (LogP), permeability, and flexibility of virtual terpolymers composed of different polyols (1,4-butanediol, glycerol, 1,3-propanediol, and 1,2-ethanediol) with adipic acid and itaconic acid. Itaconic acid, with its reactive vinyl group, acts as a chemical platform for various post-polymerization functionalizations. Poly(glycerol adipate itaconate) was selected because of its higher hydrophilicity and synthetized via solvent-free enzymatic polycondensation at 50 ◦C to prevent the isomerization or crosslinking of itaconic acid. The ecotoxicity and marine biodegradability of the resulting oligoester were assessed experimentally in order to verify its compliance with safety and sustainability criteria. Finally, the viability of the covalent linkage of biomolecules via Michael addition to the vinyl pendant of the oligoesters was verified using four molecules bearing thiol and amine nucleophilic groups: N-acetylcysteine, N-Ac-Phe-ε-Lys-OtBu, Lys-Lys-Lys, and glucosamine
Efficient biotransformation of biobased raw materials into novel polyesters/polyesteramides; comparative investigation of enzymatic synthesis of block and random copolymers and terpolymers
No full text: Within the context of paving the way for a sustainable bioeconomy, there is a strong emphasis on utilizing bio-based raw materials as substitutes for fossil fuels in the production of polymers. When designing the synthesis of novel polymeric materials from bio-based building blocks, a promising green approach consists in utilizing enzymes as biocatalysts. This aspect is particularly important when aiming to obtain products from the class of polyesters and polyesteramides with biocompatible and biodegradable properties, as enzymes facilitate the synthesis of polymers that align closely with biological systems. Lipases have been proven to be very effective in the synthesis of polymers, particularly in the ring-opening polymerization of ε-caprolactone. Considering the possibility of performing the copolymerization of ε-caprolactone for obtaining random and block structures, this is the first comparative study of the enzymatic polymer synthesis utilizing an innovative approach of combining ring-opening polymerization with polycondensation. Terpolymers derived from ε-caprolactone and dimethyl itaconate or dimethyl adipate with either 1,8-octanediol or 1,8-octanediamine were obtained at 85 °C in a solventless systems, yielding products with a copolymer content of >85 % and weight-average molecular weight (Mw) up to 40,000 Da. The thermal properties and biodegradation behavior of the synthetized terpolymers were assessed
FTIR microscopy for direct observation of conformational changes on immobilized ω-transaminase: effect of water activity and organic solvent on biocatalyst performance
Full text linkEnzyme immobilization is a key strategy to expand the scope of enzyme applications and to enable the recycling of biocatalysts, resulting in greener and more cost-efficient processes. The full exploitation of the technology advantages is strictly connected to the optimal selection of the carriers and the rational development of the immobilization protocol. The present study achieved such objectives by investigating the activity of a & omega;-transaminase in organic solvent (toluene) upon immobilization on commercially controlled porosity glass carriers (EziG & TRADE;) with diverse porosity and surface functionalization. In addition to more conventional wet-chemistry approaches and confocal microscopy, infrared microspectroscopy and imaging were exploited to highlight the enzyme distribution in a label-free manner and provide details on the immobilized enzyme's conformation with respect to the native form. Contrary to what could be expected, the highest activity of the enzyme in organic solvent was achieved for the immobilization protocol on the most hydrophilic support that more severely affects the enzyme secondary structure, promoting a beta-sheet rich folding. Experimental data show that values of water activity above 0.90 in the reaction system had a positive effect on the efficiency of the transaminase reaction. The present study represents the first example of rational development of immobilization protocols relying on direct observation of the enzyme conformation upon immobilization, shedding light on the mutual interaction between the diverse process parameters and the carrier properties
Rational Guidelines for the Two‐Step Scalability of Enzymatic Polycondensation: Experimental and Computational Optimization of the Enzymatic Synthesis of Poly(glycerolazelate)
Full text linkThe lipase catalyzed polycondensation of azelaic acid and glycerol was investigated according to a Design of Experiment approach that allowed to understand the effect of the experimental variables on monomer conversion, M n and regioselectivity of acylation of glycerol. The chemometric analysis showed that after 24h the reaction proceeds regardless of the presence of the enzyme. Accordingly, the biocatalyst was removed after a first step of synthesis and the chain elongation continued at 80°C. That allowed the removal of the biocatalyst and the preservation of its activity: pre-requites for efficient applicability at industrial scale. The experimental study, combined with docking based computational analysis, provided rational guidelines for the optimization of the regioselective acylation of glycerol. Overall, the process was scaled up to 73.5 g of monomer. The novelty of the present study stays in the rigorous control of the reaction conditions and of the integrity of the immobilized biocatalyst, thus avoiding any interference of free enzyme or fines released in the reaction mixture. The quantitative analysis of the effect of the experimental conditions and the overcoming of the major technical bottlenecks for the scalability of enzymatic polycondensation opens new scenarios for its industrial exploitation
Lipase catalysed esterification in a reactive natural deep eutectic solvent leads to lauroylcholine chloride rather than glucose ester
Full text linkEnzymatic esterification of glucose with lauric acid catalyzed by lipase B from Candida antarctica immobilized on acrylic resin (LAR) was investigated in hydrophilic reactive natural deep eutectic solvents (R-NADESs), composed of choline chloride (ChCl) as the hydrogen bond acceptor (HBA) and glucose (Glc) and water as hydrogen bond donors (HBDs) in different molar ratios. Surprisingly, no glucose esters were obtained, the only esterification product being lauroylcholine chloride, obtained in the ChCl :Glc :H2O (2: 1 : 1) ternary R-NADES. Molecular dynamic simulations clearly explained this nexpected selectivity, showing that the lipase-catalyzed synthesis of glucose lauryl esters is hindered by the manifold and strong interactions in the H-bond network and the formation of voluminous adducts of glucose with the chloride ion, which cannot access the alcohol catalytic subsite. The free choline chloride, not involved in the H-bond network of the ChCl :Glc :H2O (2 : 1 : 1) R-NADES, did enter the CalB catalytic pocket and was converted to the corresponding lauroylcholine ester
Effect of Binding Modules Fused to Cutinase on the Enzymatic Synthesis of Polyesters
Full text linkIn relation to the development of environmentally-friendly processing technologies for the continuously growing market of plastics, enzymes play an important role as green and sustainable biocatalysts. The present study reports the use of heterogeneous immobilized biocatalysts in solventfree systems for the synthesis of aliphatic oligoesters with Mws and monomer conversions up to 1500 Da and 74%, respectively. To improve the accessibility of hydrophilic and hydrophobic substrates to the surface of the biocatalyst and improve the reaction kinetic and the chain elongation, two different binding modules were fused on the surface of cutinase 1 from Thermobifida cellulosilytica.
The fusion enzymes were successfully immobilized (>99% of bound protein) via covalent bonding onto epoxy-activated beads. To the best of our knowledge, this is the first example where fused enzymes are used to catalyze transesterification reactions for polymer synthesis purposes
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