Nitrogen starvation strategies and photobioreactor design for enhancing lipid content and lipid production of a newly isolated microalga Chlorella vulgaris ESP-31: implications for biofuels.

Microalgae are recognized for serving as a sustainable source for biodiesel production. This study investigated the effect of nitrogen starvation strategies and photobioreactor design on the performance of lipid production and of CO(2) fixation of an indigenous microalga Chlorella vulgaris ESP-31. Comparison of single-stage and two-stage nitrogen starvation strategies shows that single-stage cultivation on basal medium with low initial nitrogen source concentration (i.e., 0.313 g/L KNO(3)) was the most effective approach to enhance microalgal lipid production, attaining a lipid productivity of 78 mg/L/d and a lipid content of 55.9%. The lipid productivity of C. vulgaris ESP-31 was further upgraded to 132.4 mg/L/d when it was grown in a vertical tubular photobioreactor with a high surface to volume ratio of 109.3 m(2)/m(3) . The high lipid productivity was also accompanied by fixation of 6.36 g CO(2) during the 10-day photoautotrophic growth with a CO(2) fixation rate of 430 mg/L/d. Analysis of fatty acid composition of the microalgal lipid indicates that over 65% of fatty acids in the microalgal lipid are saturated [i.e., palmitic acid (C16:0) and stearic acid (C18:0)] and monounsaturated [i.e., oleic acid (C18:1)]. This lipid quality is suitable for biodiesel production.

Yeh KL ，Chang JS 《-》

Effects of cultivation conditions and media composition on cell growth and lipid productivity of indigenous microalga Chlorella vulgaris ESP-31.

The growth and lipid productivity of an isolated microalga Chlorella vulgaris ESP-31 were investigated under different media and cultivation conditions, including phototrophic growth (NaHCO(3) or CO(2), with light), heterotrophic growth (glucose, without light), photoheterotrophic growth (glucose, with light) and mixotrophic growth (glucose and CO(2), with light). C. vulgaris ESP-31 preferred to grow under phototrophic (CO(2)), photoheterotrophic and mixotrophic conditions on nitrogen-rich medium (i.e., Basal medium and Modified Bristol's medium), reaching a biomass concentration of 2-5 g/l. The growth on nitrogen-limiting MBL medium resulted in higher lipid accumulation (20-53%) but slower growth rate. Higher lipid content (40-53%) and higher lipid productivity (67-144 mg/l/d) were obtained under mixotrophic cultivation with all the culture media used. The fatty acid composition of the microalgal lipid comprises over 60-68% of saturated fatty acids (i.e., palmitic acid (C16:0), stearic acid (C18:0)) and monounsaturated acids (i.e., oleic acid (C18:1)). This lipid composition is suitable for biodiesel production.

Yeh KL ，Chang JS 《-》

Cultivation, characterization, and properties of Chlorella vulgaris microalgae with different lipid contents and effect on fast pyrolysis oil composition.

Adamakis ID ，Lazaridis PA ，Terzopoulou E ，Torofias S ，Valari M ，Kalaitzi P ，Rousonikolos V ，Gkoutzikostas D ，Zouboulis A ，Zalidis G ，Triantafyllidis KS ... -  《-》

Effect of CO₂ supply conditions on lipid production of Chlorella vulgaris from enzymatic hydrolysates of lipid-extracted microalgal biomass residues.

The hydrolysates from lipid-extracted microalgal biomass residues (LMBRs) were used as a source of nutrients for the cultivation of Chlorella vulgaris for lipid production under various CO(2) supply conditions, including different CO(2) concentrations and aeration rates. Both parameters had a significant effect on lipid production. A CO(2) concentration of 5% was found to be most suitable for microalgal growth. Microalga grew best at a CO(2) aeration rate of 0.5 vvm. At this rate, biomass concentration and lipid productivity were at a maximum of 3.83 g L(-1) and 157 mg L(-1)d(-1), respectively, but decreased at lower or higher aeration rates. The present results showed that LMBRs utilization was effective in microalgal lipid production under suitable CO(2) supply conditions.

Zheng H ，Gao Z ，Yin F ，Ji X ，Huang H ... -  《-》

Lipid production of Chlorella vulgaris from lipid-extracted microalgal biomass residues through two-step enzymatic hydrolysis.

Lipid-extracted microalgal biomass residues (LMBRs) were treated using cellulase, neutrase and alcalase in a two-step process and the resulting hydrolysates were used as a source of nutrients for the cultivation of Chlorella vulgaris under non-aerated and aerated conditions for lipid production. Aeration was favorable for cell growth and lipid accumulation and a biomass of approximately 3.28 g L(-1), lipid content of 35% and lipid productivity of 116 mg L(-1) d(-1) were obtained. Thus, the tested mode of LMBRs utilization was effective for nutrient recycling in microalgal biodiesel production.

Zheng H ，Gao Z ，Yin F ，Ji X ，Huang H ... -  《-》