Lipid extractions from docosahexaenoic acid (DHA)-rich and oleaginous Chlorella sp. biomasses by organic-nanoclays

[Display omitted] •Comparison of lipid extractions for Chlorella sp. with low- and high-lipid content.•Lipid extractions of wet microalgae biomasses by four organic-nanoclays.•∼100% conversion of the extracted lipid’s fatty acids to biodiesel.•One of most effective lipid extraction in wet microalgal biomass. Microalgae biorefinement has attracted in intensive academic and industrial interest worldwide for its potential to replace petrol biofuels as economically and environmentally advantageous alternatives. However, harvesting and lipid extraction remain as critical and difficult issues to be resolved. In the present study, four amino-groups functionalized organic-nano clays were prepared. Specifically, Mg or Al or Ca backboned and covalently linked with 3-aminopropyltriethoxysilane or 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane by sol–gel reaction under ambient conditions, resulted in Mg–APTES clay, Al–APTES clay, Ca–APTES clay, and Mg–N3 clay, respectively. Each organic-nanoclay was utilized for lipid extraction from wet microalgae biomass. As a result, the lipid-extraction efficiency of paste docosahexaenoic acid (DHA)-rich Chlorella sp. with low lipid content was high, while one of paste oleaginous Chlorella sp. with high lipid content was relatively low. Despite the low lipid-extraction efficiencies in all of the wet microalgae biomass, the conversion of the extracted lipids’ fatty acids to biodiesel was nearly 100%.