Lipid extraction from wet Chaetoceros muelleri culture and evaluation of remaining defatted biomass

Abstract

Microalgae-based lipids are considered a good feedstock for various applications, including biodiesel and omega-3-rich oil production. However, developing new lipid extraction and recovery techniques are required to make microalgal oil a more economically competitive feedstock. To avoid the costly process of complete drying of algal biomass, extraction from wet slurry was improved. Potentially cost-effective and scalable processes were investigated and developed that enable total rupture of nutrient-starved microalgal cells to facilitate lipid recovery directly from wet algal slurry, including pretreatments (thermal treatment, UV-C light radiation and osmotic shock) and the use of a solvent mixture. Using hexane and ethanol on UV-C and thermally pre-treated algal slurries led to more than doubling of the total extractable lipids and total transesterifiable lipids, compared to biomass that was not pretreated and when hexane only was used as the solvent. Lipids (25% w/dry weight), triacylglycerol (13%) and fatty acid methyl esters (17%) were recovered from UV-C pre-treated algal slurry (1000mJ/cm2 UV-C). The residual defatted biomass was analysed for further applications and contained carbohydrates (≈15% w/dry weight) that may be suitable for bioethanol production through fermentation.