Yanjun Jiang

Pickering emulsion stabilized by lipase-containing periodic mesoporous organosilica particles: A robust biocatalyst system for biodiesel production

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.

Immobilization of horseradish peroxidase in phospholipid-templated titania and its applications in phenolic compounds and dye removal

In this study, horseradish peroxidase (HRP) was encapsulated in phospholipid-templated titania particles through the biomimetic titanification process and used for the treatment of wastewater polluted with phenolic compounds and dye. The encapsulated HRP exhibited improved thermal stability, a wide range of pH stability and high tolerance against inactivating agents. It was observed an increase in Km value for the encapsulated HRP (8.21 mM) when compared with its free counterpart. For practical applications in the removal of phenolic compounds and dye by the encapsulated HRP, the removal efficiency for phenol, 2-chlorophenol, Direct Black-38 were 92.99%, 87.97%, and 79.72%, respectively, in the first treatment cycle. Additionally, the encapsulated HRP showed better removal efficiency than free HRP and a moderately good capability of reutilization.

Immobilization of Candida antarctica lipase B by adsorption in organic medium

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.

Reactive extraction and in situ self-catalyzed methanolysis of germinated oilseed for biodiesel production

Compared with conventional production of biodiesel from oilseeds, in situ reactive extraction of oilseeds with acyl acceptors is an attractive approach, which consists of sustainable, economically attractive biotechnological processes for biodiesel synthesis. In this study, the presence of lipase activity in germinating oilseeds was detected and the lipase activity increased to a maximum after 4 days of germination. At that time, the germinated seeds featured an only slightly lower oil content relative to the ungerminated seeds. As such, an environmentally friendly and low-cost in situ self-catalytic process for biodiesel production was developed. The biodiesel was prepared by reactive extraction of germinated Jatropha curcas L. seeds with methanol without any other catalyst added. In this process, n-hexane was used as reactive extraction solvent. The highest fatty acid methyl esters (FAMEs) yield of 87.6% could be achieved under the optimum conditions: a n-hexane/germinated seed ratio of 2.5 ml g−1, a methanol/germinated seed oil (contained approximately 90% FFA) molar ratio of 1.5:1, a reaction temperature of 35 °C, a germinated seed water content of 2.9% and a reaction time of 8 h. This simple reactive extraction process without additional catalyst can be a potential route for biodiesel production, which may greatly reduce the processing steps and costs.

Comparison of the Properties of Lipase Immobilized onto Mesoporous Resins by Different Methods

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.

In situ self-catalyzed reactive extraction of germinated oilseed with short-chained dialkyl carbonates for biodiesel production.

In order to eliminate the expense associated with solvent extraction and oil cleanup, and reduce the processing steps in biodiesel production, reactive extraction has become a focus of research in recent years. In this study, germinated castor seed was used as substrate and catalyst, dimethyl carbonate (DMC) was used as acyl acceptor and oil extractant to produce biodiesel. The optimum conditions were as follows: the germination time of castor seed was 72 h, DMC/germinated seed ratio was 12.5 ml/g, reaction temperature was 35°C, and water content was 2.11%. The biodiesel yield could reach as much as 87.41% under the optimized conditions. This germinated oilseed self-catalyzed reactive extraction can be a promising route for biodiesel production.

Co-aggregation of Laccase and Nature Egg White: a Simple Method to Prepare Stable and Recyclable Biocatalyst

Cross-linked enzyme aggregates (CLEAs) are a versatile and effective method for enzyme immobilization, which is exquisitely simple and amenable to rapid optimization. In this study, nature egg white, which is low cost, easily available, and nontoxic, was used as protein feeder to replace traditional protein feeder (bovine serum albumin, etc.) in the preparation of laccase CLEAs (CLEAs-egg). The effects of the various parameters—nature of the precipitant, temperature, glutaraldehyde concentration, and cross-linking time—on the activity recovery of the resulting CLEAs were studied. The laccase CLEAs-egg exhibited increased stability compared to the free and the laccase CLEAs without protein feeder. The thermal stability of CLEAs-egg was improved and showed 1.3- and 1.8-fold increase in activity at 40 and 60xa0°C after 5xa0h incubation, respectively. The stability of CLEAs-egg against denaturants (urea and GndHCl) and protease (trypsin) was also improved. Laccase CLEAs-egg was also demonstrated to be an active and stable biocatalyst in the removal of chlorophenol. After 30xa0h, 83.6 and 91.5xa0% of 4-chlorophenol and 2,4-dichlorophenol can be removed.

Immobilized Lipase from Candida sp. 99–125 on Hydrophobic Silicate: Characterization and Applications

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.

Heterogeneous Catalyst Derived from Waste Shells for Biodiesel Production

The catalysts derived from waste shells were employed to produce biodiesel from Jatropha curcas oil. The catalysts were characterized by scanning electron microscopy, Fourier transform infrared, and powder X-ray diffraction studies. Under the best reaction conditions (temperature 65°C, methanol/oil molar ratio 9:1, reaction time 3 h, and catalyst loading 3 wt% of oil), a high biodiesel yield of more than 99.0% was obtained. After ultrasonic mixing, the time for reaction completion could be shortened. After reuse for seven times, about 75% of the fatty acid methyl esters yield could be obtained. The activity of the catalysts could be revived absolutely after recalcination.

Optimization and kinetic study of immobilized lipase-catalyzed synthesis of ethyl lactate

Abstract Enzymatic synthesis of ethyl lactate catalyzed by immobilized lipase has been investigated. The reaction variables (including the molar ratio of ethanol to acid, total substrate amount, temperature, reaction time and rotation speed) were selected in accordance with the Plackett–Burman design and were further optimized via response surface methodology. The molar ratio of ethanol to acid, total substrate amount and reaction time were screened out as significant variables for the optimization study. A 20-run, full-factorial, central composite design was used to construct the statistical model and the optimal conditions obtained were as follows: molar ratio of ethanol to acid of 8.3:1, total substrate amount of 0.4 g, reaction time of 26.87 h with temperature of 55°C and rotation speed of 150 rpm. Under the optimal conditions, the yield of ethyl lactate was up to 24.32%; close to the 25.13% obtained using the commercial lipase, Novozym 435. Due to the low cost and simple immobilization process, the lipase prepared in the present work could have great potential in enzymatic applications. Additionally, a kinetic model with inhibition by both ethanol and lactic acid following a ping-pong bi-bi mechanism was proposed.