Lipid recovery from Nannochloropsis gaditana using the wet pathway: Investigation of the operating parameters of bead milling and centrifugal extraction

The aim of this work is to track and optimize lipid recovery from Nannochloropsis gaditana in wet extraction operations. No significant differences in biomass concentration were found when disrupting microalgal suspensions of up to 30 g/L dry weight, but disruption efficiency differed depending on their physiological states. It took 5.8 min in a bed milling device to disrupt 80% of the cells in a nitrogen-depleted culture (10–30 g/L), compared to 4.8 min for a nitrogen-replete culture (10–30 g/L). The fatty acids released were then recovered by two different methods: one using a centrifugal partition extractor device and the other using a continuous centrifugal extractor device. For the latter, Box-Behnken RSM analysis showed that the interaction between biomass concentration and solvent inlet rate had the greatest influence on lipid recovery. Up to 84% of the triacylglycerol was recovered using 7.9 g/L of algal suspension at 5.4 mL/min, and treated with 8.9 mL/min of 2-methyl-tetra-hydrofuran. •N deplete culture of N.gaditana becomes more resistant to bead milling disruption•2-methyl-tetra-hydrofuran was chosen as the best of three solvents with 84% extraction efficiency•Triacylglycerol wet extraction for biodiesel was optimized by Box-Benhken experimental design•Biomass concentration, solvent and biomass flow rates were found main parameters•Centrifugal extraction combined to bead milling have achieved 73% of Triacylglycerol recovery