Search

For conversion of biomass-derived levulinic acid into alkyl levulinates, a novel kind of lipase-based biocatalyst was prepared through immobilized lipase B from C. antarctica (CALB) on organosilica material with highly ordered 3D macroporous organosilica frameworks and a 2D hexagonal meso-structure (named 3DOM/m-OS) for the first time. The catalytic performance of the immobilized lipase (NER@3DOM/m-OS) was investigated. NER@3DOM/m-OS was used as biocatalyst to catalyze the esterification reaction between levulinic acid (LA) and n-butanol. Under optimized reaction conditions, 74.59% of ester yield was achieved after 12h of reaction. NER@3DOM/m-OS was also used to production of other alkyl levulinates, the ester yields increased to 84.51% (octyl levulinate) and 91.14% (dodecyl levulinate), respectively. When NER@3DOM/m-OS was used repeatedly in batch reactions, the ester yields of n-butyl, octyl, and dodecyl levulinate could retain 46.18%, 82.33% and 81.25% after 9 reaction cycles, respectively, which was better than commercial lipase Novozym 435 under the same condition., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Dopmine functionalized mesoporous onion-like silica (DPMS) was synthesized via a biomimetic coating, and lipase Candida sp. 99-125 (LCS) was immobilized in DPMS (LCS@DPMS) by physical adsorption in this study. The DPMS was characterized by SEM, TEM, BET and FT-IR, and it was shown that the DPMS had clear multishell structures with large surface area of 419 m 2 /g. The activity, pH stability, thermal stability, storage stability, and reusability of the LCS@DPMS were investigated in detail. The stabilities of LCS@DPMS were improved significantly compared to the free lipase and LCS@MS (LCS immobilized in unfunctionalized mesoporous onion-like silica by physical adsorption). All the results indicated that the DPMS had high efficiency and improved stability for lipase immobilization.

Mesoporous silica nanoparticles were synthesized by using tannic acid as a pore-forming agent, which is an environmentally friendly, cheap, and non-surfactant template. SEM and TEM images indicated that the tannic acid-templated mesoporous silica nanoparticles (TA-MSNs) are monodisperse spherical-like particles with an average diameter of 195 ± 16 nm. The Brunauer-Emmett-Teller (BET) results showed that the TA-MSNs had a relatively high surface area (447 m(2)/g) and large pore volume (0.91 cm(3)/g), and the mean pore size was ca. 10.1 nm. Burkholderia cepacia lipase was immobilized on the TA-MSNs by physical adsorption for the first time, and the properties of immobilized lipase (BCL@TA-MSNs) were investigated. The BCL@TA-MSNs exhibited satisfactory thermal stability; strong tolerance to organic solvents such as methanol, ethanol, isooctane, n-hexane, and tetrahydrofuran; and high operational reusability when BCL@TA-MSNs were applied in esterification and transesterification reactions. After recycling 15 times in the transesterification reaction for biodiesel production, over 85 % of biodiesel yield can be maintained. With these desired characteristics, the TA-MSNs may provide excellent candidates for enzyme immobilization.

Lipase Candida sp. 99-125 has been proved to be quite effective in catalyzing organic synthesis reactions and is much cheaper than commercial lipases. Mesoporous silicates are attractive materials for the immobilization of enzymes due to their unique structures. The present research designed a hydrophobic silicate with uniform pore size suitable for the comfort of lipase Candida sp. 99-125 for improving its activity and stability. The resulting immobilized lipase (LP@PMO) by adsorption was employed to catalyze hydrolysis, esterification, and transesterification reactions, and the performances were compared with the lipase immobilized on hydrophilic silicate (LP@PMS) and native lipase. The LP@PMO showed as high activity as that of native lipase in hydrolysis and much increased catalytic activity and reusability in the reactions for biodiesel production. Besides, LP@PMO also possessed better organic stability. Such results demonstrate that immobilization of lipase onto hydrophobic supports is a promising strategy to fabricate highly active and stable biocatalysts for applications.

With the aim to provide a highly stable and active biocatalyst, cross-linked enzyme aggregates (CLEAs) of lipase Candida sp. 99-125 were prepared in three-dimensionally ordered macroporous silica materials (CLEAs-LP@3DOM-SiO2). Lipase Candida sp. 99-125 was first precipitated in the pores of 3DOM SiO2 (named EAs-LP@3DOM-SiO2), and further cross-linked by glutaraldehyde to form CLEAs-LP@3DOM-SiO2. Saturated ammonium sulfate was used as a precipitant and glutaraldehyde with a concentration of 0.25% (w/w) was employed as a cross-linker. Compared with EAs-LP@3DOM-SiO2 and native lipase, CLEAs-LP@3DOM-SiO2 exhibited excellent thermal and mechanical stability, and could maintain more than 85% of initial activity after 16 days of shaking in organic and aqueous phase. When CLEAs-LP@3DOM-SiO2 was applied in esterification and transesterification reactions, improved activity and reusability were achieved. This method can be used for the immobilization of other enzymes of interest.

A novel catalytic system of Pickering emulsion stabilized by lipase-containing periodic mesoporous organosilica was constructed (named LP@PE) and used as biocatalyst for biodiesel production. The reaction parameters were optimized and the optimum conditions were as follows: the water fraction 0.65%, molar ratio of ethanol to oleic acid 2:1, immobilized lipase particles 150mg, phosphate buffer pH 7.0 and temperature 30°C. Under these conditions, the maximum biodiesel yield obtained via esterification of oleic acid with ethanol could reach 95.8%. The biodiesel yield could maintain 88.6% after LP@PE was used 15times. The LP@PE was also used in the synthesis of biodiesel from Jatropha curcas oil. The highest yield could reach 87.1% and the yield was 73.0% after 10 cycles. All these results demonstrated that Pickering emulsion system stabilized by immobilized enzyme may possess much potential in many enzymatic industrial applications., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Genipin, a natural cross-linking agent, was used for the immobilization of lipase from Candida sp. 99-125 by cross-linking to two kinds of mesoporous resins. Under optimum conditions, the activity recovery of immobilized lipase on resin NKA-9 could reach up to 96.99% when the genipin concentration was 0.5%, and it could reach up to 86.18% for S-8 with a genipin concentration of 0.25%. Compared with using glutaraldehyde as a cross-linking agent, the immobilized lipase using genipin showed better pH and thermal stability, storage stability, and reusability. The residual activity of immobilized lipase using genipin as cross-linker remained more than 60% of its initial activity after six hydrolytic cycles, whereas only about 35% activity remained by using glutaraldehyde as cross-linker.

Candida antarctica lipase B (CALB) was immobilized on the macroporous resin by physical adsorption in organic medium. The immobilization was performed in 5 mL isooctane, and the immobilization conditions were optimized. The results were achieved with the mass ratio of lipase to support 1:80, the buffer of pH 6.0, initial addition of PBS 75 microL, and immobilization time of two hours at 30 degrees C. Under the optimal conditions, the activity recovery was 83.3%. IM-CALB presented enhanced pH and thermal stability compared to the free lipase, and showed comparable stability with the commercial Novozym 435, after 7 times repeated use for catalyzing the synthesis of ethyl lactate, 56.9% of its initial activity was retained, and only 24.7% was retained when used for catalyzing the hydrolysis of olive oil., (Copyright 2009 Elsevier B.V. All rights reserved.)

We investigated the transesterification of crude cottonseed oil with methyl acetate to biodiesel, by using Lipozyme TL IM and Novozym 435 as catalysts. Results showed that the biodiesel yield significantly increased with the addition of methanol into the reaction system, and the highest biodiesel yield of 91.83% was achieved with the optimum conditions as follows: n-hexane as solvent, molar ratio of methyl acetate to oil 9:1, 3% methanol based on the oil mass to inhibit the creation of acetic acid, 10% Lipozyme TL IM and 5% Novozym 435 as catalyst based on the oil mass, reaction temperature 55 degrees C and reaction time 8 h. Additionally, we explored the kinetics of lipase-catalyzed crude cottonseed oil to biodiesel, and proposed a kinetic model.

The kinetics of lipase-catalyzed interesterification synthesis of L-ascorbyl lactate was studied. To determine the enzyme kinetic constants of the interesterification, a three-factor and five-level central composite design was used. The factors studied were ethyl lactate concentration, reaction temperature (T), and water content (w). Moreover, a statistical approach called the response surface method (RSM) was used to predict the kinetic constants. Finally, the relationships between the kinetic constants (Vm and Km) and the reaction parameters (T and w) were obtained. To assess the accuracy of the RSM approach for determining Vm and Km, detailed validation experiments were carried out by the conventional approach at four different reaction parameters(35 degrees C, 10 microL; 45 degrees C, 20 microL; 55 degrees C, 15 microL; 65 degrees C, 18 microL). The results indicated that the RSM approach gave reasonable results for the determination of Vm and Km in the range of tested parameters.

BACKGROUND Enzymatic production of biodiesel is an alternative solution to circumvent the problems associated with chemical catalysis. However, the drawbacks, including lower stability and reusability of the lipase, often make this route unfeasible for industrial application. RESULTS A stable biocatalyst system was prepared by trapping an aqueous solution of Burkholderiacepacia lipase ( BCL) in bead-shaped silicone microspheres (named lipase-based static emulsions). Compared with free BCL, lipase-based static emulsions showed outstanding stability under vigorous shaking conditions and the thermal stability was improved. The lipase-based static emulsions were employed to catalyze the transesterification of soybean oil with ethanol for biodiesel production. Under the optimum conditions, about 95.42% of FAEE yield was achieved in 30 h. In addition, the lipase-based static emulsions presented good reusability, and the FAEE yield remained at more than 70.63% after 15 successive reaction cycles. The lipase-based static emulsions were also used to catalyze the transesterification of jatropha oil and cottonseed oil with ethanol for biodiesel production, and the maximum FAEE yield was 96.10% and 90.39%, respectively. CONCLUSIONS Lipase-based static emulsions were developed as robust biocatalysts by trapping an aqueous solution of lipase in silicone microspheres. The lipase-based static emulsions catalyzed process may be a suitable technique for biodiesel production. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Highlights • Meso-molding three-dimensionally ordered macroporous alumina was successfully prepared. • Three different enzymes were immobilized onto glutaraldehyde-activated NH 2 -3DOM/m-Al. • Immobilized enzymes exhibited enhanced thermal stability and good operational stability. Abstract The meso-molding three-dimensionally ordered macroporous alumina (3DOM/m-Al) was synthesized via a dual-templating approach (polystyrene (PS) colloidal crystals as hard template and triblock copolymer P123 as soft template) with hydrous aluminum isopropoxide as precursor. The obtained 3DOM/m-Al was characterized, and the results showed that 3DOM/m-Al had ordered macropores (ca. 300 nm in diameter) with wormhole-like mesopores, relatively high surface areas (338.1 m2/g), large pore volumes (0.4030 cm3/g) and tunable pore sizes. The amino functionalized 3DOM/m-Al by aminopropyltriethoxysilane (APTES) was activated by glutaraldehyde and used as support for the immobilization of three different commercial enzymes (Lipase B from Candida antarctica (CALB), penicillin G acylase (PGA) and nitrile hydratase (NHase)). The result of confocal laser scanning microscopy (CLSM) indicated that the enzyme was successfully immobilized onto glutaraldehyde-activated NH 2 -3DOM/m-Al. The effect of the immobilized conditions on the specific activity of enzymes was investigated. Compared with free enzymes, the immobilized enzymes exhibited enhanced thermal stability. The three immobilized enzymes (CALB@NH 2 -3DOM/m-Al, PGA@NH 2 -3DOM/m-Al and NHase@NH 2 -3DOM/m-Al) were applied for the synthesis of palmitic acid, 6-aminopenicillanic acid (6-APA) and acrylamide, respectively. After recycling 10 times, CALB@NH 2 -3DOM/m-Al, PGA@NH 2 -3DOM/m-Al and NHase@NH 2 -3DOM/m-Al retained approximately 76%, 87% and 52% of their initial activities, respectively, indicating that the immobilized enzymes had good operational stability. Therefore, this work documented herein provides a versatile platform for enzyme immobilization with several inherent advantages. [ABSTRACT FROM AUTHOR]

The synthesis of silica-based colloidosome with a magnetic solid core via Pickering emulsification and its use as an immobilized enzyme system is described in this work. Lipase B from Candida antarctica (CALB) was physically adsorbed on the material to form the immobilized enzyme (LP@colloidosome) and the enzyme loading was 166.3 mg/g support . The specific hydrolytic activity of LP@colloidosome was 209.6 U/g support and its immobilization yield was 22.08%. The stability test indicated that LP@colloidosome can retain 49% of original activity after incubation at 50 °C for 6 h and 105.6% of original activity after incubation in t -butanol for 96 h, while the free lipase lost most the initial activity under the same condition. These findings showed that LP@colloidosome had the enhanced thermal stability and tolerance in organic solvents. Meanwhile, LP@colloidosome can be easily recovered by magnet due to the addition of modified Fe 3 O 4 nanoparticles in the solid core. LP@colloidosome was successfully used to catalyze the esterification of fatty acids and alcohols with different length in organic solvent. The yields of the corresponding esters that catalyzed by LP@colloidosome were significantly higher than those catalyzed by free lipase. Additionally, the versatility of LP@colloidosome was also verified in the synthesis of glycerol carbonate through transesterification. The results indicated that biosynthesis of glycerol carbonate from glycerol using the LP@colloidosome (6.1 wt%) as catalyst afforded 85.20% of conversion rate at 60 °C. This work offers insight into the design of colloidosome for efficient immobilization of lipase as well as improvement of the lipase’s properties. [ABSTRACT FROM AUTHOR]

• A new activated hNF-lipase was synthesized. • Ca2+ not only induced self-assemble of nanoflowers, but also activated the lipase from A. oryzae. • Tween-80 acts as an excellent activator for lipase from A. oryzae. • The activated hNF-lipase exerted enhanced enzymatic and stability. Lipase-inorganic hybrid nanoflowers were prepared using Ca 3 (PO 4) 2 as the inorganic component and lipase from Aspergillus oryzae (A. oryzae) as the organic component. The influences of metal ions with different valence, various additives (surfactant), and synthesis conditions on the activity of the lipase hybrid nanoflowers were systematically investigated. Results revealed that the valence state of metal ions played an important role on the shape and activity of lipase hybrid nanoflowers. The synthesized lipase hybrid nanoflowers using bivalence metal ions (Ca2+, Mn2+, and Zn2+) as the inorganic components exhibited relative high activity. However, very low activities were observed in the lipase hybrid nanoflowers using univalent metal ions (Ag+) or trivalent metal ions (Al3+, Fe3+). More importantly, Ca2+ not only induced self-assemble of lipase hybrid nanoflowers, but also activated the enzyme activity by inducing conformational changes in lipase from A. oryzae. As a result, lipase/Ca 3 (PO 4) 2 hybrid nanoflowers (hNF-lipase) exhibited the high activity. The hNF-lipase displayed 9, 12, and 61 folds higher activity than lipase/Ag 3 PO 4 hybrid nanoflowers, lipase/AlPO 4 hybrid nanoflowers, and lipase/FePO 4 nanoflowers, respectively. Compared with free lipase, the hNF-lipase displayed 172 % increase in activities by using 0.15 mM Tween-80 as an activity inducer (activated hNF-lipase). Furthermore, the hNF-lipase and activated hNF-lipase exhibited increased stability against high temperature and denaturant, and had good storage stability and reusability. [ABSTRACT FROM AUTHOR]