Zhaoan Chen

Increased lipid production of the marine oleaginous microalgae Isochrysis zhangjiangensis (Chrysophyta) by nitrogen supplement

Effects of nitrate feeding on the cell growth and lipid accumulation of marine microalgae Isochrysis zhangjiangensis were investigated. When nitrate was supplied at interval of 24h, instead of 72 h, a high lipid content of 40.9% and a biomass density of 3.1 g L(-1) were obtained. To confirm whether I. zhangjiangensis accumulates lipid during nitrogen-repletion, a two-stage cultivation method was applied. This algal strain had a high lipid content during sustained nitrate addition and showed a high carbohydrate content under nitrate-depletion conditions. These results revealed that this algal strain can accumulate lipids under nitrogen-repletion conditions and accumulate carbohydrate under nitrogen-depletion conditions. When cultured in an extremely high nitrate concentration, 9 g L(-1) at 24h intervals, the growth of algal cells was suppressed, but the highest lipid content of 53% was attained. This special characteristic of lipid accumulation makes I. zhangjiangensis an ideal candidate for producing biodiesel using N-rich wastewater.

Optimization of carbon dioxide fixation and starch accumulation by Tetraselmis subcordiformis in a rectangular airlift photobioreactor

Culture conditions are very important to CO 2 bio-fixation and carbohydrate accumulation in microalgae. The objective of this study was to optimize semi-continuous culture conditions of Tetraselmis subcordiformis in a rectangular airlift photobioreactor for obtaining maximized carbon dioxide fixation rate and intracellular starch productivity. The effects of the initial biomass concentration (0.13, 0.8, 1.8, 2.8 and 3.47 g L -1 ), the gas flow rate (0.03, 0.1, 0.2, 0.3 and 0.37 V V -1 m -1 ) and different carbon dioxide concentrations (1.63, 5, 10, 15 and 18.37%) were considered using a central composite design. By using response surface methodology and the desirability function approach, the optimal CO 2 fixation rate of 55.15 mg L -1 h -1 and the intracellular starch productivity of 10.66 mg L -1 h -1 occurred when the initial biomass concentration was 1120 mg L -1 and the air supplemental CO 2 concentration was 6.9% with a gas flow rate of 0.35 V V -1 m -1 . These results suggest the potential of applying T. subcordiform to CO 2 mitigation and starch production. Key words : Photobioreactor, CO 2 fixation rate, starch productivity, response surface methodology, desirability function approach.

The production of light olefins by catalytic cracking of the microalga Isochrysis zhanjiangensis over a modified ZSM-5 catalyst

This study investigated the catalytic cracking of the microalga Isochtysis zhanjiangensis over a modifled ZSM-5 catalyst with the aim of producing C2-C4 light olefins. Compared with the thermal cracking process, the catalytic cracking of this microalga displayed higher selectivity for and greater yield of these olefins. The catalytic cracking of extracted lipids and the corresponding residues of the microalga was also examined, and the results showed that the lipids could be efficiently converted to light olefins. The catalytic cracking of lipids extracted by different solvents demonstrated that neutral lipids gave the highest yield of light olefins at 36.7%. The yields of light olefins obtained from catalytic cracking of the extraction residues were much lower than the yields obtained from lipids, and thus the lipids, especially the neutral lipids, are the primary contributors to the generation of light olefins. Isochrysis zhanjiangensis with an elevated neutral lipid content will therefore give the highest yield of light olefins through catalytic cracking

Membrane cartridges for endotoxin removal from interferon preparations

The suitability of membrane cartridges for the removal of endotoxin from both distilled water and interferon preparations was examined. The endotoxin concentrations were reduced to 4.0 and 7.3 EU/ml, respectively, when about 4000 ml of distilled water with 20 and 28 EU/ml were passed through the deoxycholate and chitosan immobilized membrane cartridges. When 200 ml of interferon preparation with endotoxin concentration more than 80 EU/ml and pH 3.9 were applied to a deoxycholate immobilized membrane cartridge at a flow-rate of 9 ml/min, the endotoxin concentration was reduced to less than 10 EU/ml. However, if an interferon preparation of 450 ml, with more than 80 EU/ml of endotoxin and pH 3.9 was applied to the chitosan immobilized membrane cartridge at a flow-rate of 18 ml/min, the endotoxin concentration was reduced to less than 10 EU/ml.

Catalytic pyrolysis of microalga Chlorella pyrenoidosa for production of ethylene, propylene and butene

This paper investigated the process of catalytic pyrolysis of lipid-rich microalga Chlorella pyrenoidosa for the production of light olefins (ethylene, propylene and butene). A modified ZSM-5 zeolite catalyst was used in the reactions, and it had high selectivity for the light olefins production. The catalytic pyrolysis performances of microalga Chlorella pyrenoidosa in nitrogen and steam reaction atmospheres were investigated. The catalytic pyrolysis performances in one-step and two-step processes were investigated and compared. The effects of reaction temperatures and water flow rates on the catalytic pyrolysis performances were also explored. The results showed that higher yield of light olefins was obtained in the steam reaction atmosphere as compared with that in the nitrogen atmosphere. The carbon yield of light olefins obtained from two-step catalytic pyrolysis was nearly three times that from one-step catalytic pyrolysis. The two-step catalytic pyrolysis process also facilitated the production of aromatic hydrocarbons in the liquid products. The maximum carbon yield of light olefins could reach 31.9% in the two-step process under the reaction temperature of 923 K and water flow rate of 30 ml h−1.

Modeling of protein adsorption in membrane affinity chromatography

Abstract For the design of affinity membranes protein adsorption in membrane affinity chromatography (MAC) was studied by frontal analysis. According to fast mass transfer, small thickness of affinity membranes and high affinity between the protein and the ligand, an ideal adsorption (IA) model was proposed for MAC and was used together with equilibrium‐dispersive (E‐D) model to describe the adsorption of bovine serum albumin (BSA) onto cellulose diacetate/polyethyleneimine (CA/PEI) blend membranes with and without Cu2+ chelating. E‐D model was found to better describe the initial region of experimental breakthrough curves. The influence of axial dispersion was revealed and it showed the importance of design of the module to homogenously distribute feed solution. IA model was found to be better for the whole experimental breakthrough curve. According to it, the capacity of affinity membranes and the specificity of the interaction are of equal importance for the design of affinity membranes. An optimum feed concentration was also found in the operation of MAC. The discrepancy between experimental optimum feed concentrations and predicted ones from IA model may be due to the ignorance of some experimental effects such as axial dispersion.

[Subcellular localization and identification of hydrogenase isolated from the marine green alga Platymonas subcordiformis using immunoprecipitation and MALDI-TOF MS].

A marine unicellular green alga, Platymonas subcordiformis, was demonstrated to photobiologically produce hydrogen gas from seawater. The objective of this study was to localize and identify the hydrogenase isolated from P. subcordiformis. Adaptation in the presence of inhibitors of protein biosynthesis indicated that the hydrogenase was much more inhibited by cycloheximide than that by chloramphenicol. The result suggested that the hydrogenase isolated from P. subcordiformis is probably synthesized in cytoplasmic ribosomes. Both Western blot analysis and immunogold electron microscopy demonstrate that the P. subcordiformis hydrogenase is mainly located in the chloroplast stroma. The proteins that reacted specifically with the antibodies against the iron hydrogenase isolated from Chlamydomonas reinhardtii were concentrated by immunoprecipitation. The separated protein bands were cut out of the SDS-PAGE gel, in-gel digested by trypsin, and analyzed by Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). Mascot was employed for analysis of the MALDI data using the public databases NCBInr. The hydrogenase isolated from P. subcordiformis was identified to be the Fe-hydrogenase.

Investigation of photoinduced electron transfer based on immobilized Green microalga Tetraselmis subcordiformis photoanode

A microalga Tetraselmis subcordiformis (synonym: Platymonas subcordiformis) based photoanode was prepared by a novel method developed in our lab. In a three-electrode configuration, photocurrent and photosynthetic oxygen evolution were measured synchronously. The effects of three site-specific inhibitors (CCCP, DCMU and DBMIB) on photocurrent response of microalgal photoanode were investigated and discussed. The results indicated that the electrons of photocurrent originated from the photosynthetic electron transfer chain of microalga. In further discussion on specific roles of CCCP during biohydrogen photoproduction from Tetraselmis subcordiformis, it was estimated that CCCP at 15 uM inhibited about 34% of PS II activity as ADRY agent and about 51% of PS II activity as uncoupler.