Yung-Chuan Liu

Continuous Production of Lipase-Catalyzed Biodiesel in a Packed-Bed Reactor: Optimization and Enzyme Reuse Study

An optimal continuous production of biodiesel by methanolysis of soybean oil in a packed-bed reactor was developed using immobilized lipase (Novozym 435) as a catalyst in a tert-butanol solvent system. Response surface methodology (RSM) and Box-Behnken design were employed to evaluate the effects of reaction temperature, flow rate, and substrate molar ratio on the molar conversion of biodiesel. The results showed that flow rate and temperature have significant effects on the percentage of molar conversion. On the basis of ridge max analysis, the optimum conditions were as follows: flow rate 0.1 mL/min, temperature 52.1°C, and substrate molar ratio 1 : 4. The predicted and experimental values of molar conversion were 83.31 ± 2.07% and 82.81 ± .98%, respectively. Furthermore, the continuous process over 30 days showed no appreciable decrease in the molar conversion. The paper demonstrates the applicability of using immobilized lipase and a packed-bed reactor for continuous biodiesel synthesis.

Exploiting immobilized metal affinity membranes for the isolation or purification of therapeutically relevant species.

Increasing reports regarding the isolation or purification of biospecies for therapeutic purpose using the immobilized metal affinity chromatography have been presented in recent years. At the same time, membrane chromatography technique has also gained more and more attention for their advantage in speeding the separation process. The immobilized metal affinity membrane technique developed by combining these two techniques may provide an alternative potential tool for separating the therapeutically relevant biospecies. In this review paper, the features of the immobilized metal affinity membranes are discussed and concentrated on three subtopics: membrane matrices, immobilized metal affinity method, and membrane module designs. Several examples of practically applying the immobilized metal affinity membranes on the purification of potential therapeutics reported in the literature are subsequently presented. Lastly, this review also provides an overall evaluation on the possible advantages and problems existing in this technique to point out opportunities and further improvements for more applied development of the immobilized metal affinity membranes.

Differential gene expression of livers from ApoE deficient mice

A genomic survey for differentially expressed genes was performed to livers of ApoE deficient mice using human cDNA microarray containing approximately 9,000 human cDNA clones. Due to the homology between mouse and human, hybridization was performed at lower stringency condition, 10 degrees below the regular hybridizing temperature. Gene expression profiles of livers corresponding to high levels of blood cholesterol were generated at genomic scale. Thirty-seven genes were randomly selected from a pool of differentially expressed genes and subjected to semi-quantitative RT-PCR, further confirmed the result from microarray hybridization. These included genes associated with atherosclerosis, and novel genes that implied novel pathways correlated to high levels of blood cholesterol. It is promising using human cDNA microarray, the most complete collection among all species, to study other mammalian systems with satisfying speed and accuracy.

Lipase-immobilized biocatalytic membranes for biodiesel production.

Microbial lipase from Candida rugosa (Amano AY-30) has good transesterification activity and can be used for biodiesel production. In this study, polyvinylidene fluoride (PVDF) membrane was grafted with 1,4-diaminobutane and activated by glutaraldehyde for C. rugosa lipase immobilization. After immobilization, the biocatalytic membrane was used for producing biodiesel from soybean oil and methanol via transesterification. Response Surface Methodology (RSM) in combination with a 5-level-5-factor central composite rotatable design (CCRD) was employed to evaluate the effects of reaction time, reaction temperature, enzyme amount, substrate molar ratio and water content on the yield of soybean oil methyl ester. By ridge max analysis, the predicted and experimental yields under the optimum synthesis conditions were 97% and 95%, respectively. The lipase-immobilized PVDF membrane showed good reuse ability for biodiesel production, enabling operation for at least 165 h during five reuses of the batch, without significant loss of activity.

Evaluation and application of conducting polymer entrapment on quartz crystal microbalance in flow injection immunoassay

An immunosensor employing conducting polymer entrapment (CPE) method to immobilize immuno-protein on the quartz crystal microbalance (QCM) for clinical flow-injection-analysis (FIA) purpose was exploited. By comparing the CPE approach and the conventional physical immobilization (PI) method, a frequency shift of the former was 47% higher than that of the latter when measuring at 0.5 mg/ml human serum albumin antibody concentration. This implied that CPE was a feasible approach for developing QCM-FIA process. An immunoassay of anti-pseudorabies virus antibody in mouse sera further exemplified its practical potential in diagnostic implication.

Characteristics of the photosynthesis microbial fuel cell with a Spirulina platensis biofilm.

A novel design of a photosynthetic microbial fuel cell (PMFC) is constructed. It is a membrane-less and mediator-free apparatus with a gilding gold mesh as an anode and a graphite carbon cloth as a cathode. The electrode spacing is 4 cm. Spirulina platensis is aggregated and deposited on the anode to form a thin biofilm. Results show that the chlorophyll (Chl) content of the biofilm attributed the PMFCs electricity performance. The open circuit voltage (OCV) reading of PMFC is proportional to Chl content when the Chl was below 0.5mg. The maximal OCV of PMFC is 0.49 V. When the PMFC was connected to an external resistance of 1 kΩ, a maximum power density of 10 mW m(-2) was obtained. This designed PMFC yielded competitively high OCV and power density as compared to other microbial fuel cells reported in the literature.

Ultrasonic-Assisted Extraction of the Botanical Dietary Supplement Resveratrol and Other Constituents of Polygonum cuspidatum

The roots of Polygonum cuspidatum produce several phenolic compounds, including trans-resveratrol (1), trans-piceid (2), and emodin (3), and are a commercial source of the botanical dietary supplement 1. Ultrasonic-assisted extraction technology and conventional shaking extraction procedures were compared for the extraction of 1-3 from P. cuspidatum roots, using 50% ethanol as a food grade solvent. These compounds were extracted successfully, and their mass transfer coefficients were calculated by fitting the experimental results to a model derived from Ficks second law. The results indicated that ultrasonic-assisted extraction had higher mass transfer efficacies and extraction yields for 1-3 as compared with conventional shaking extraction. Under the extraction conditions used (extraction temperature 50 °C; ultrasonic power 150 W), yields of 3.5, 9.2, and 7.8 mg/g were obtained for 1-3, respectively.

Effect of membranes with various hydrophobic/hydrophilic properties on lipase immobilized activity and stability

In this study, three membranes: regenerated cellulose (RC), glass fiber (GF) and polyvinylidene fluoride (PVDF), were grafted with 1,4-diaminobutane (DA) and activated with glutaraldehyde (GA) for lipase covalent immobilization. The efficiencies of lipases immobilized on these membranes with different hydrophobic/hydrophilic properties were compared. The lipase immobilized on hydrophobic PVDF-DA-GA membrane exhibited more than an 11-fold increase in activity compared to its immobilization on a hydrophilic RC-DA-GA membrane. The relationship between surface hydrophobicity and immobilized efficiencies was investigated using hydrophobic/hydrophilic GF membranes which were prepared by grafting a different ratio of n-butylamine/1,4-diaminobutane (BA/DA). The immobilized lipase activity on the GF membrane increased with the increased BA/DA ratio. This means that lipase activity was exhibited more on the hydrophobic surface. Moreover, the modified PVDF-DA membrane was grafted with GA, epichlorohydrin (EPI) and cyanuric chloride (CC), respectively. The lipase immobilized on the PVDF-DA-EPI membrane displayed the highest specific activity compared to other membranes. This immobilized lipase exhibited more significant stability on pH, thermal, reuse, and storage than did the free enzyme. The results exhibited that the EPI modified PVDF is a promising support for lipase immobilization.

High Yield of Wax Ester Synthesized from Cetyl Alcohol and Octanoic Acid by Lipozyme RMIM and Novozym 435

Wax esters are long-chain esters that have been widely applied in premium lubricants, parting agents, antifoaming agents and cosmetics. In this study, the biocatalytic preparation of a specific wax ester, cetyl octanoate, is performed in n-hexane using two commercial immobilized lipases, i.e., Lipozyme® RMIM (Rhizomucor miehei) and Novozym® 435 (Candida antarctica). Response surface methodology (RSM) and 5-level-4-factor central composite rotatable design (CCRD) are employed to evaluate the effects of reaction time (1–5 h), reaction temperature (45–65 °C), substrate molar ratio (1–3:1), and enzyme amount (10%–50%) on the yield of cetyl octanoate. Using RSM to optimize the reaction, the maximum yields reached 94% and 98% using Lipozyme® RMIM and Novozym® 435, respectively. The optimum conditions for synthesis of cetyl octanoate by both lipases are established and compared. Novozym® 435 proves to be a more efficient biocatalyst than Lipozyme® RMIM.

Purification of penicillin G acylase using immobilized metal affinity membranes

The immobilized metal affinity membrane (IMAM) with modified regeneration cellulose was employed for purification of penicillin G acylase (PGA). For studying PGA adsorption capacity on the IMAM, factors such as chelator surface density, chelating metal, loading temperature, pH, NaCl concentration and elution solutions were investigated. The optimal loading conditions were found at 4 degrees C, 0.5 M NaCl, 32.04 micromol Cu(2+) per disk with 10 mM sodium phosphate buffer, pH 8.5, whereas elution conditions were: 1 M NH(4)Cl with 10 mM sodium phosphate buffer, pH 6.8. By applying these chromatographic conditions to the flow experiments in a cartridge, a 9.11-fold purification in specific activity with 90.25% recovery for PGA purification was obtained. Meanwhile, more than eight-times reusability of the membrane was achieved with the EDTA regeneration solutions.