Bio-energy is arousing the common interest of worldwide researchers to investigate it as a substitute for fossil resources. Compared to other bio-energy sources, algae energy has many advantages. This research was aimed to increase the lipid productivity of Dunaliella tertiolecta, an oleaginous microalgae, by optimizing algal culture medium. Plackett–Burman Design (PBD) was adopted to screen out the critical factors from seven nutritional elements. Box–Behnken design (BBD) was used to seek the optimal nutritional conditions for achieving maximum lipid productivity. Results showed that four nutrients, i.e. NaNO3, NaCl, NaHCO3 and NaH2PO4 2H2O, played a critical role in the accumulation of lipid. GC analysis verified that the four critical nutrients mentioned above had different influences on fatty acid methyl esters, moreover, NaCl had the most prominent effects on fatty acid composition of D. tertiolecta. NaCl 87.69 g L−1, NaNO3 1.77 g L−1, NaH2PO4·2H2O 1.92 g L−1, NaHCO3 5.57 g L−1 were proven to be the optimal culture conditions, under which the lipid productivity in the experiment was 12.576 ± 0.12 mg per L per day, which is approaching the theoretically predicted lipid productivity of 12.925 mg per L per day. The lipid productivity was increased by 31.4% under the optimal culture conditions compared to that under the initial medium composition, indicating that optimization of nutrients could effectively improve the lipid production of D. tertiolecta.
Yu Chen,Rentao Mu,Mingde Yang,Lina Fang,Yulong Wu,Kejing Wu,Ya Liu,Jinlong Gong
This paper describes catalytic consequence of hydrothermal liquefaction (HTL) of Dunaliella tertiolecta ( D. tertiolecta ) over carbon nanotubes (CNTs) supported metals catalysts to produce bio-oil. When Co/CNTs is used as catalysts, the conversion and bio-oil yield increase to 95.78 and 40.25 wt.%, respectively. Chemical analysis results showed that the introduction of catalyst significantly affected the chemical composition of bio-oil with a higher percentage of hydrocarbons and a lower content of fatty acid. The introduction of metal into CNTs had no change in the basic CNT skeleton and the loaded metal nanoparticles encapsulated within the CNT enhances the disorder and defects in CNTs . Based on our results and the literature, the plausible general reaction and catalytic HTL pathways of D. tertiolecta are proposed.
Microalgal lipid is considered as a potential biodiesel resource due to its advantages compared to other bioresources. The production of biofuel from microalgae includes several stages like microalgae cultivation, biomass harvest, biomass treatment, lipid extraction, and the ultimate biodiesel synthesis. Lipid extraction is closely associated with the productivity and cost of energy production. In the present study, lipid of green algae Dunaliella tertiolecta was extracted by chemical agents with involvement of ultrasound and microwave. The optimization of experimental conditions was carried out by response surface methodology and orthogonal test design. Using the ultrasonic technique, an extraction rate of 45.94% was obtained under the optimum conditions of ultrasonic power 370 W, extraction time 5 min and liquid/solid ratio 125 mL/g. The extraction rate of 57.02% was obtained by the means of microwave assistance under the optimized conditions of extraction time 160 s, microwave power 490 W and liquid/solid ratio 100 mL/g. The comparison of the two results indicated microwave was more effective than ultrasound in extracting process. When the two techniques were utilized in combination, the optimized condition was ultrasonic power 320 W, ultrasonic time 4 min, microwave power 280 W, microwave time 120 s and liquid/solid ratio 100 mL/g, and the extraction rate was 49.97%.
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