The CIDES process: Fractionation of concentrated microalgal paste for co-production of biofuel, nutraceuticals, and high-grade protein feed

Abstract This study examined a process for fractionating concentrated pastes of nitrogen replete Nannochloropsis sp. biomass using scalable equipment for application in a microalgal biorefinery. In the CIDES process (Concentration, Incubation, Disruption, Extraction and Separation) highly concentrated microalgal paste (11–23 wt.%) was incubated at moderate temperature (35 °C) under low agitation (60 rpm) before undergoing mechanical cell disruption by high-pressure homogenization (one pass, 1000 bar) and hexane extraction at a low solvent-to-biomass ratio (~ 3:1 w / w ). Incubation disaggregated microalgal cells and increased their susceptibility to mechanical rupture by high pressure homogenization leading to improved lipid recovery by hexane extraction. Upon centrifugation, the extraction mixture separated to four layers: hexane layer, emulsion layer, aqueous layer and cell debris layer. After solvent recovery, the neutral lipid in the hexane layer can be converted to biodiesel. The emulsion layer consisting of intact cells, cell fragments, residual hexane and water, can be combined with a polar co-solvent (such as isopropanol) to recover high-value ω-3 fatty acids as nutraceuticals. The nutrient-rich aqueous layer can be recycled to cultivation ponds, while the protein-rich (ca 50 wt.% of dry biomass), lipid-depleted and solvent-free cell debris layer can be directly used as livestock or aquaculture feed.