Influence of the alkyl-substituted silane precursor on sol–gel encapsulated lipase activity

Green and Sustainable Hot Melt Adhesive (HMA) Based on Polyhydroxyalkanoate (PHA) and Silanized Cellulose Nanofibers (SCNFs)

Polyhydroxyalkanoate (PHA), with a long chain length and high poly(4-hydroxybutyric acid) (P4HB) ratio, can be used as a base polymer for eco-friendly and biodegradable adhesives owing to its high elasticity, elongation at break, flexibility, and processability; however, its molecular structures must be adjusted for adhesive applications. In this study, surface-modified cellulose nanofibers (CNFs) were used as a hydrophobic additive for the PHA-based adhesive. For the surface modification of CNFs, double silanization using tetraethyl orthosilicate (TEOS) and methyltrimethoxysilane (MTMS) was performed, and the thermal and structural properties were evaluated. The hydrophobicity of the TEOS- and MTMS-treated CNFs (TMCNFs) was confirmed by FT-IR and water contact angle analysis, with hydrophobic CNFs well dispersed in the PHA. The PHA-CNFs composite was prepared with TMCNFs, and its morphological analysis verified the good dispersion of TMCNFs in the PHA. The tensile strength of the composite was enhanced when 10% TMCNFs were added; however, the viscosity decreased as the TMCNFs acted as a thixotropic agent. Adding TMCNFs to PHA enhanced the flowability and infiltration ability of the PHA-TMCNFs-based adhesive, and an increase in the loss tangent (Tan δ) and adjustment of viscosity without reducing the adhesive strength was also observed. These changes in properties can improve the flowability and dispersibility of the PHA-TMCNFs adhesive on a rough adhesive surface at low stress. Thus, it is expected that double-silanized CNFs effectively improve their interfacial adhesion in PHA and the adhesive properties of the PHA-CNFs composites, which can be utilized for more suitable adhesive applications.

Thermally Stable and Reusable Ceramic Encapsulated and Cross-Linked CalB Enzyme Particles for Rapid Hydrolysis and Esterification

Candida antarctica lipase B (CalB) enzyme was encapsulated and cross-linked by silica matrix to enhance its thermal stability and reusability, and demonstrated an enzymatic ability for rapid hydrolysis and esterification. Silica encapsulated CalB particles (Si-E-CPs) and silica cross-linked CalB particles (Si-CL-CPs) were prepared as a function of TEOS concentration. The particle size analysis, thermal stability, catalytic activity in different pHs, and reusability of Si-E-CPs and Si-CL-CPs were demonstrated. Furthermore, the determination of the CalB enzyme in Si-E-CPs and Si-CL-CPs was achieved by Bradford assay and TGA analysis. Enzymatic hydrolysis was performed against the p-nitrophenyl butyrate and the catalytic parameters (K_m, V_max, and K_cat) were calculated by the Michaelis–Menten equation and a Lineweaver–Burk plot. Moreover, enzymatic synthesis for benzyl benzoate was demonstrated by esterification with an acyl donor of benzoic acid and two acyl donors of benzoic anhydride. Although the conversion efficiency of Si-CL-CPs was not much higher than that of native CalB, it has an efficiency of 91% compared to native CalB and is expected to be very useful because it has high thermal and pH stability and excellent reusability.

Enhancing Activity by Supercritical CO2 Mediated Immobilization of Lipase on Mesocellular Foam in Preparation of Hexyl Laurate

Hexyl laurate is employed in several cosmetics having great demand. It could be synthesized catalytically like a "natural" perfume using a lipase. The use of mesocellular foam silica (MCF) for immobilization of lipases could be made using supercritical CO₂ as a medium to enhance its activity in comparison with the normal techniques. Three different catalysts were supported on MCF such as Candida antractica B (CALB), Amano AYS, and Porcine pancreas (PPL), and their activity was evaluated in the preparation of hexyl laurate from lauric acid and hexyl alcohol. CALB@ MCF was the best among all. A systematic study was conducted to assess the effects of different operating parameters. It was ternary complex mechanism with inhibition by hexyl alcohol. The enzyme was reusable and the process is green.

Lipase Immobilization on Silica Xerogel Treated with Protic Ionic Liquid and its Application in Biodiesel Production from Different Oils

Treated silica xerogel with protic ionic liquid (PIL) and bifunctional agents (glutaraldehyde and epichlorohydrin) is a novel support strategy used in the effective immobilization of lipase from Burkholderia cepacia (LBC) by covalent binding. As biocatalysts with the highest activity recovery yields, LBC immobilized by covalent binding with epichlorohydrin without (203%) and with PIL (250%), was assessed by the following the hydrolysis reaction of olive oil and characterized biochemically (Michaelis⁻Menten constant, optimum pH and temperature, and operational stability). Further, the potential transesterification activity for three substrates: sunflower, soybean, and colza oils, was also determined, achieving a conversion of ethyl esters between 70 and 98%. The supports and the immobilized lipase systems were characterized using Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), elemental analysis, and thermogravimetric (TG) analysis.

Engineering aspects of immobilized lipases on esterification: A special emphasis of crowding, confinement and diffusion effects

Cross-linked enzyme crystal (CLEC) and sol-gel entrapped pseudomonas sp. lipase were investigated for the esterification of lauric acid with ethanol by considering the effects of reaction conditions on reaction rate. The activation energy for the reaction was estimated to be 1097.58 J/mol and 181.75 J/mol for sol-gel and CLEC entrapped lipase respectively. CLEC lipase exhibited a marginal internal diffusion effect on reaction rate over sol-gel lipases and found to be interesting. The overall reaction mechanism was found to conform to the Ping Pong Bi Bi mechanism. The higher efficiency of sol-gel lipases over CLEC lipases in esterification reaction is mainly due to the combined effects of crowding, confinement and diffusional limitations.

Design and Preparation of Nano-Lignin Peroxidase (NanoLiP) by Protein Block Copolymerization Approach

This study describes the preparation of nanoprotein particles having lignin peroxidase (LiP) using a photosensitive microemulsion polymerization technique. The protein-based nano block polymer was synthesized by cross-linking of ligninase enzyme with ruthenium-based aminoacid monomers. This type polymerization process brought stability in different reaction conditions, reusability and functionality to the protein-based nano block polymer system when compared the traditional methods. After characterization of the prepared LiP copolymer nanoparticles, enzymatic activity studies of the nanoenzymes were carried out using tetramethylbenzidine (TMB) as the substrate. The parameters such as pH, temperature and initial enzyme concentration that affect the activity, were investigated by using prepared nanoLip particles and compared to free LiP. The reusability of the nano-LiP particles was also investigated and the obtained results showed that the nano-LiP particles exhibited admirable potential as a reusable catalyst.

Sol-gel approach for extracting highly versatile aspirin and its metabolites using MISPE followed by GC-MS/MS analysis

AIM

Aspirin is known to be a salicylate drug widely used as an analgesic, antipyretic and anti-inflammatory drug.

METHODOLOGY

Sol-gel based nanosized molecularly imprinted polymer (nMIP) has been synthesized for extraction of aspirin and its metabolites in urine followed by GC-MS/MS analysis.

RESULTS

Binding affinity of nMIP and nonimprinted polymer was found to be in the range of 70-95% and 29-45%, respectively. LOD and LOQ of aspirin and its metabolites were found to be in the range of 0.63-2.4 ng/ml and 2.07-7.68 ng/ml, respectively.

CONCLUSION

The developed method was found to be applicable for routine analysis of aspirin and its metabolites in biological samples.

Cellulase stabilization by crosslinking with ethylene glycol dimethacrylate and evaluation of its activity including in a water–ionic liquid mixture

Synthesis of immobilized enzymes via crosslinking is an easy route to develop a biocatalyst with enhanced activity and recyclability.

Encapsulation in a sol-gel matrix of lipase from Aspergillus niger obtained by bioconversion of a novel agricultural residue

Lipase from Aspergillus niger was obtained from the solid-state fermentation of a novel agroindustrial residue, pumpkin seed flour. The partially purified enzyme was encapsulated in a sol-gel matrix, resulting in an immobilization yield of 71.4 %. The optimum pH levels of the free and encapsulated enzymes were 4.0 and 3.0, respectively. The encapsulated enzyme showed greater thermal stability at temperatures of 45 and 60 °C than the free enzyme. The positive influence of the encapsulation process was observed on the thermal stability of the enzyme, since a longer half-life t 1/2 and lower deactivation constant were obtained with the encapsulated lipase when compared with the free lipase. Kinetic parameters were found to follow the Michaelis-Menten equation. The K m values indicated that the encapsulation process reduced enzyme-substrate affinity and the V max was about 31.3 % lower than that obtained with the free lipase. The operational stability was investigated, showing 50 % relative activity up to six cycles of reuse at pH 3.0 at 37 °C. Nevertheless, the production of lipase from agroindustrial residue associated with an efficient immobilization method, which promotes good catalytic properties of the enzyme, makes the process economically viable for future industrial applications.

Immobilization and characterisation of a lipase from a new source, Bacillus sp. ITP-001

A new source of lipase from Bacillus sp. ITP-001 was immobilized by physical adsorption on the polymer poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) in aqueous solution. The support and immobilized lipase were characterised, compared to the lyophilised lipase, with regard to the specific surface area, adsorption-desorption isotherms, pore volume (V(p)) and size (dp) by nitrogen adsorption, differential scanning calorimetry, thermogravimetric analysis, chemical composition analysis, Fourier transform infrared spectroscopy and biochemical properties. The immobilized enzyme displayed a shift in optimum pH towards the acidic side with an optimum at pH 4.0, whereas the optimum pH for the free enzyme was at pH 7.0; the optimum temperature of activity was 80 and 37 °C for the free and immobilized enzyme, respectively. The inactivation rate constant for the immobilized enzyme at 37 °C was 0.0038 h⁻¹ and the half-life was 182.41 h. The kinetic parameters obtained for the immobilized enzyme gave a Michaelis-Menten constant (K(m)) of 49.10 mM and a maximum reaction velocity (V(max)) of 205.03 U/g. Furthermore, the reuse of the lipase immobilized by adsorption allowed us to observe that it could be reused for 10 successive cycles, duration of each cycle (1 h), maintaining 33 % of the initial activity.

Immobilization of Candida rugosa lipase on poly(3-hydroxybutyrate-co-hydroxyvalerate): a new eco-friendly support

The overall objective of this study is to evaluate the morphological [scanning electron microscopy (SEM)], physicochemical [differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), chemical composition analysis, Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR)], and biochemical properties of Candida rugosa lipase (CRL) immobilized on a natural biopolymer poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) in aqueous solution. CRL was immobilized by physical adsorption with efficiency of 30%. Compared with free CRL enzyme, there were slight changes in immobilized CRL activity as a function of temperature (from 37°C to 45°C), but a similar optimal pH value of 7.0. Inactivation rate constants for immobilized CRL enzyme were 0.009 and 0.334 h−1, and half-lives were 77 and 2 h at 40°C and 60°C, respectively. Kinetic parameters obtained for immobilized CRL include the Michaelis–Menten constant of K  m = 213.18 mM and maximum reaction velocity of V  max = 318.62 U/g. The operational stability of immobilized CRL was tested repeatedly, and after 12 cycles of reuse, the enzyme retained 50% activity. Based on our results, we propose that PHBV-immobilized CRL could serve as a promising biocatalyst in several industrial applications.

Evaluation of the catalytic properties of Burkholderia cepacia lipase immobilized on non-commercial matrices to be used in biodiesel synthesis from different feedstocks

The objective of this work was to produce an immobilized form of lipase from Burkholderia cepacia (lipase PS) with advantageous catalytic properties and stability to be used in the ethanolysis of different feedstocks, mainly babassu oil and tallow beef. For this purpose lipase PS was immobilized on two different non-commercial matrices, such as inorganic matrix (niobium oxide, Nb(2)O(5)) and a hybrid matrix (polysiloxane-polyvinyl alcohol, SiO(2)-PVA) by covalent binding. The properties of free and immobilized enzymes were searched and compared. The best performance regarding all the analyzed parameters (biochemical properties, kinetic constants and thermal stability) were obtained when the lipase was immobilized on SiO(2)-PVA. The superiority of this immobilized system was also confirmed in the transesterification of both feedstocks, attained higher yields and productivities.

Improvement of catalytic properties of lipase from Arthrobacter sp. by encapsulation in hydrophobic sol-gel materials

In this work, lipase from Arthrobacter sp. was immobilized by sol-gel encapsulation to improve its catalytic properties. Various silanizing agents including vinyl-trimethoxy silane, octyl-trimethoxy silane, gamma-(methacryloxypropyl)-trimethoxy silane (MAPTMS) and tetraethoxysilane (TEOS) were chosen as the precursors. Among them, MAPTMS was for the first time utilized to encapsulate lipases, and the prepared enzyme by copolymerization of MAPTMS and TEOS exhibited the highest activity in both the hydrolysis of p-nitrophenyl palmitate and the asymmetric acylation of 4-hydroxy-3-methyl-2-(2-propenyl)-2-cyclopenten-1-one. The effects of various immobilization parameters were investigated. Under the optimum conditions of MAPTMS/TEOS=1/1 (mol/mol), water/silane molar ratio (R value)=20 and lipase loading=0.01 g/mL sol, the total activity of the immobilized enzyme reached up to 13.6-fold of the free form. Moreover, the encapsulated lipase exhibited higher thermal stability than the free form and retained 54% of the original activity after uses for 60 d. Enantioselectivity of enzyme was also improved with an E value of 150 after encapsulation from 85 for the free form.

Covalent attachment of Candida rugosa lipase on chemically modified hybrid matrix of polysiloxane–polyvinyl alcohol with different activating compounds

Candida rugosa lipase was immobilized by covalent binding on hybrid matrix of polysiloxane-polyvinyl alcohol chemically modified with different activating agents as glutaraldehyde, sodium metaperiodate and carbonyldiimidazole. The experimental results suggested that functional activating agents render different interactions between enzyme and support, producing consequently alterations in the optimal reaction conditions. Properties of the immobilized systems were assessed and their performance on hydrolytic and synthetic reactions were evaluated and compared with the free enzyme. In hydrolytic reactions using p-nitrophenyl palmitate as substrate all immobilized systems showed higher thermal stability and optima pH and temperature values in relation to the free lipase. Among the activating compounds, carbonyldiimidazole resulted in a total recovery of activity on the support and the highest thermal stability. For the butyl butyrate synthesis, the best performance (molar conversion of 95% and volumetric productivity of 2.33 g L(-1)h(-1)) was attained with the lipase immobilized on POS-PVA activated with sodium metaperiodate. The properties of the support and immobilized derivatives were also evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopies and chemical composition (FTIR).

Application of SiO2-poly(dimethylsiloxane) hybrid material in the fabrication of amperometric biosensor

Silica xerogel was widely used in the development of biosensors by coupling the desired biological components to various transducers. Unfortunately, the application of xerogels is limited due to their poor mechanical properties and poor structural maintenance of entrapped biomaterials. In this study, the availability of poly(dimethylsiloxane) (PDMS)-modified silica sol-gel (TEOS/PDMS Ormosil) glass in the immobilization of enzymes and its application in the fabrication of amperometric biosensor was investigated. We demonstrated that most of activity of encapsulated horseradish peroxidase can be preserved in PDMS-modified SiO2 glass compared with conventional silica xerogel. The synthesized monoliths exhibited high transparency and crack-free. The enzyme electrode based on glucose oxidase encapsulated TEOS/PDMS Ormosil glass on Pd electrode was fabricated and characterized electrochemically. The characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The biosensor exhibited a series of good properties: high sensitivity (1.63 microA mM(-1) analyte), short response time and high reproducibility. The results indicate that TEOS/PDMS Ormosil glass has great potential to the immobilization of biomaterials as well as the fabrication of biosensors.