Li-Hua Cheng

Enhanced lipid production of Chlorella vulgaris by adjustment of cultivation conditions.

To increase the lipid productivity and thus to reduce the production cost of microalgal biodiesel, effects of cultivation conditions including KNO(3)-level, CO(2) concentration and irradiance on the cell growth, chlorophyll a content and lipid accumulation of Chlorella vulgaris were systematically investigated in a membrane sparged photobioreactor. The biochemical compositions including carbohydrates, proteins and lipids were analyzed simultaneously by the FT-IR spectroscopy. The results showed that the largest biomass productivity and the highest lipid content were obtained at different cultivation conditions. The algae should be harvested at a point that optimized the biomass productivity and lipid content. When the cultivation conditions were controlled at 1.0mM KNO(3), 1.0% CO(2) and 60 micromol photons m(-2)s(-1) at 25 degrees C, the highest lipid productivity obtained was 40 mg L(-1)d(-1), which was about 2.5-fold that had been reported by Illman et al. (2000). The influences of cultivation conditions on the cell growth, lipid accumulation, and other biochemical compositions of cells were further discussed and illustrated by a schematic which was also useful for other microalgal species.

Evaluation of FT-IR and Nile Red methods for microalgal lipid characterization and biomass composition determination.

To characterize lipid content of microalgal cells rapidly and accurately, the gravimetric determination, FT-IR and Nile Red (NR) staining were investigated on six typical eukaryotic and prokaryotic algae species. FT-IR and Nile Red were relative quantification methods and a standard curve was required in contrast to the gravimetric method. The FT-IR method determined the lipid, carbohydrate and protein contents simultaneously assuming that the algal cells only consisted of those three components. The Nile Red method was a relatively rapid method for neutral lipid content characterization by spectrofluorometry and could locate lipid body of the algal cell by fluorescence microscopy. According to sample sources and processing purposes, the gravimetric determination was preferable for large-scale cultivation with low-frequency monitoring, while FT-IR and Nile Red were suitable for general laboratory cultivation with medium-frequency monitoring, in particularly Nile Red was appropriate for small samples when high-frequency screening was required.

Effect of carbon source on biomass growth and nutrients removal of Scenedesmus obliquus for wastewater advanced treatment and lipid production.

The combination of tertiary wastewater treatment and microalgal lipid production is considered to be a promising approach to water eutrophication as well as energy crisis. To intensify wastewater treatment and microalgal biofuel production, the effect of organic and inorganic carbon on algal growth and nutrient removal of Scenedesmus obliquus were examined by varying TOC (total organic carbon) concentrations of 20-120mgL(-1) in wastewater and feeding CO2 concentrations in the range of 0.03-15%, respectively. The results showed that the maximal biomass and average lipid productivity were 577.6 and 16.7mgL(-1)d(-1) with 5% CO2 aeration. The total nitrogen, total phosphorus and TOC removal efficiencies were 97.8%, 95.6% and 59.1% respectively within 6days when cultured with real secondary municipal wastewater. This work further showed that S. obliquus could be utilized for simultaneous organic pollutants reduction, N, P removal and lipid accumulation.

Saline wastewater treatment by Chlorella vulgaris with simultaneous algal lipid accumulation triggered by nitrate deficiency.

Chlorella vulgaris, a marine microalgae strain adaptable to 0-50 g L(-1) of salinity, was selected for studying the coupling system of saline wastewater treatment and lipid accumulation. The effect of total nitrogen (T N) concentration was investigated on algal growth, nutrients removal as well as lipid accumulation. The removal efficiencies of TN and total phosphorus (TP) were found to be 92.2-96.6% and over 99%, respectively, after a batch cultivation of 20 days. To illustrate the response of lipid accumulation to nutrients removal, C. vulgaris was further cultivated in the recycling experiment of tidal saline water within the photobioreactor. The lipid accumulation was triggered upon the almost depletion of nitrate (<5 mg L(-1)), till the final highest lipid content of 40%. The nitrogen conversion in the sequence of nitrate, nitrite, and then to ammonium in the effluents was finally integrated with previous discussions on metabolic pathways of algal cell under nitrogen deficiency.

Study on membrane reactors for biodiesel production by phase behaviors of canola oil methanolysis in batch reactors

In comparison with the general stirring batch reactor, the membrane reactor has been reported to have higher molar ratios of methanol to oil but ultralow catalyst concentration in the biodiesel production. In this research, the methanolysis of canola oil is conducted in a stirring batch reactor in the presence of NaOH as a catalyst. Based on the investigation of the effects of operating conditions, including methanol to oil molar ration, catalyst concentrations and temperatures, the time course of the reaction path for the reactant composition in the ternary phase diagram of oil-FAME-MeOH offers an effective way to understand the operation of membrane reactors in the biodiesel production. The results show that increasing the residence time of the whole reactant system within the two-phase zone is good for the separation operation through the membranes.

Application of memberane dispersion for enhanced lipid milking from Botryococcus braunii FACHB 357

To improve the mixing efficiency in an aqueous-tetradecane system and thus to increase the lipid milking efficiency, poly (ether sulfones) hollow fiber membrane was applied as dispersion medium to establish an in situ lipid extraction process from Botryococcus braunii FACHB 357. The lipid location of this microalga was characterized by fluorescence microscope and transmission electron microscopy, respectively. The results showed that B. braunii excreted lipids into the outer matrix, which allowed it possible to extract algal lipids in situ by organic solvent. Within an aqueous-organic biphasic system, the lipid extraction ratio of tetradecane increased from 38.05% to 50.15% by introducing a microporous membrane as the dispersion medium, mainly because smaller solvent droplets were produced. Under this experimental condition (the volume ratio of tetradecane: 10%, the flow rate: 10 ml min(-1)), solvent toxicity and shearing stress had not shown significant impact on algal cells viability in 96 h. Within the same time period, the lipid amount extracted by solvent was enhanced with the increase of the solvent flow rate and the initial biomass concentration. These results suggested membrane dispersion was a good choice to improve mixing effect in the algal lipid milking process or other similar cell products extracted processes.

Concentration of lignocellulosic hydrolyzates by solar membrane distillation

A small solar energy collector was run to heat lignocellulosic hydrolyzates through an exchanger, and the heated hydrolyzate was concentrated by vacuum membrane distillation (VMD). Under optimal conditions of velocity of 1.0m/s and 65°C, glucose rejection was 99.5% and the flux was 8.46Lm(-2)h(-1). Fermentation of the concentrated hydrolyzate produced 2.64 times the amount of ethanol as fermentation using the original hydrolyzate. The results of this work indicated the possibility to decrease the thermal energy consumption of lignocellulosic ethanol through using VMD.

Mechanism of lipid extraction from Botryococcus braunii FACHB 357 in a biphasic bioreactor.

Algal lipid of Botryococcus braunii could be produced continuously and in situ extracted in an aqueous-organic bioreactor. In this study, the cell ultra-structure and cell membrane permeability of B. braunii FACHB 357 were investigated to understand the mechanism of lipid extraction within the biphasic system. The results showed that biocompatible solvent of tetradecane could induce algal lipid accumulation, enable the cell membrane more active and the cell wall much looser. The exocytosis process was observed to be one of the mechanisms for lipid cross-membrane extraction in the presence of organic solvent.

A novel polysulfone-based affinity membrane with high hemocompatibility: preparation and endotoxin elimination performance

A polysulfone (PSF)-based hollow fiber affinity membrane for in vitro endotoxin elimination was explored and prepared successfully. This depended on the well-known hemocompatibility of PSF membrane. The PSF hollow fiber membranes were firstly activated by a chloromethylation reaction, and treated with ethylenediamine and glutaraldehyde successively. L-Serine (Ser) was finally immobilized on the surface of the membranes as the functional ligand. The modified membrane was confirmed by X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and contact angle analysis. L-Ser density up to 8.4 μmol cm−2 on PSF membranes could be achieved. The adsorption performance was preliminarily studied by comparing the PSF membrane and PSF–Ser membrane in deionized water and sodium phosphate buffer, showing that the PSF–Ser membrane had improved endotoxin adsorption capacity with decreased Bovine Serum Albumin (BSA) adsorption. The PSF–Ser membrane was further investigated in human plasma, and showed excellent removal efficiency and specificity for endotoxin. These results demonstrate the promising application potential of this novel affinity membrane in sepsis therapy.

Preparation of Thin Film Composite Nanofiltration Membrane by Interfacial Polymerization with 3,5-Diaminobenzoylpiperazine and Trimesoyl Chloride

Abstract A new aromatic diamine, 3,5-diaminobenzoylpiperazine (3,5-DABP), was synthesized from 3,5-diaminobenzoic acid and 1-formyl piperazine. The structure of 3,5-DABP was identified by FT-IR spectra and 1 H NMR spectra. With 3,5-DABP as aqueous monomer and trimesoyl chloride (TMC) as organic monomer, thin film composite (TFC) nanofiltration membranes were prepared by interfacial polymerization technology. The salt rejection order of these TFC membranes is Na 2 SO 4 >MgSO 4 >MgCl 2 >NaCl. This sequence indicates that the membranes are negatively charged.