After 5 h pretreatment, lipid yields of Exp. 1–3 were similar to that of untreated algal biomass (dashed line), whereas Exp. 4 shows a 22% increase compared to untreated algal biomass. 24 h
pretreatment by different concentrations of FNA enhanced lipid yields dramatically compared to those achieved using untreated algal biomass. The lipid yields of Exp. 4 after 24 h pretreatment generated an 89% increase over untreated algal biomass, to as high as 17.0 ± 1.5% (wt% of dried algal biomass). This result is even 4% higher than the yield from algal biomass by standard microwave pretreatment which has been reported as one of the most efficient pretreatment methods for the tested green algae, vegetables and animal feeds (Lee et al., 2010; Mahesar et al., 2008; Virot et al., 2008). With longer pretreatment, lipid yields up to 48 h pretreatment
kept increasing. The degree of increase was heightened by increasing FNA concentration. For Exp. 3 and 4, yielded lipid content reached 19.0 ± 0.1% and 21.9 ± 0.2% (wt% of dried algal biomass)
respectively, a 2.1-fold and 2.4-fold increase over the untreated algae, which confirms the potential of using FNA as a pretreatment technique to aid lipid extraction from algal biomass