Novel strategy for microalgae cell disruption and wet lipid extraction by employing electro-Fenton process with sacrificial steel anode.

Electro-Fenton process (EFP) was studied as a potential cell disruption technique for recovery of lipids from wet biomass of the microalga Chlorella homosphaera. A novel approach of electrochemical dissolution of a sacrificial steel anode was used to provide Fe2+ required to initiate EFP and microalgae cell disruption. Response surface methodology (RSM) was employed to optimize the process parameters and maximize the lipid yield of EFP. The RSM model (R2 = 90.66%, Adj.R2 = 87.71%) showed that a maximum lipid yield of 18.29% could be obtained at 40 min reaction time and 4.38 g/L biomass concentration. Experimental validation resulted in a lipid yield of 19.99 ± 1.33%, which was significantly higher than wet lipid extraction without cell disruption. However, the lipid yield of EFP should be further improved to achieve comparable results to mechanical cell disruption methods. Nonetheless, biodiesel synthesized from lipids obtained via EFP conformed to the ASTM D6751-12 standard.

Comparative assessment of pretreatment strategies for production of microalgae-based biodiesel from locally isolated Chlorella homosphaera.

The yield and quality of lipids extracted from microalgal biomass are critical factors in the production of microalgae-based biodiesel. The green microalga Chlorella homosphaera, isolated from Beira Lake, Colombo, Sri Lanka was employed in the present study to identify the effect of chlorophyll removal and cell disruption methods on lipid extraction yield, fatty acid methyl ester (FAME) profile and quality parameters of biodiesel; including cetane number (CN), iodine value (IV), degree of unsaturation (DU) and high heating value (HHV). In the first section of this study, chlorophyll was removed from dry microalgae biomass prior to lipid extraction. Through the analysis of FAME profiles, it was observed that chlorophyll removal yielded biodiesel of enhanced quality, albeit with a lipid loss of 44.2% relative to the control. In the second section of the study, mechanical cell disruption strategies including grinding, autoclaving, water bath heating and microwaving were employed to identify the most effective method to improve lipid recovery from chlorophyll-removed microalgae biomass. Autoclaving (121 °C, 20 min sterilization time, total time 2 h) was the most effective cell disruption technique of the methods tested, in terms of lipid extraction yield (39.80%) and also biodiesel quality. Moreover, it was observed that employing cell disruption subsequent to chlorophyll removal has a significant impact on the FAME profile of microalgae-based biodiesel, and consequently served to increase HHV and CN although IV and DU did not vary significantly.