Effective lipid extraction from algae cultures using switchable solvents

Abstract

A new procedure based on switchable polarity solvents (SPS) was proposed for lipid extraction of wet algal samples or cultures, thereby circumventing the need for an energy intensive drying step and facilitating easy recovery of the lipids from the extraction liquid. Lipids were extracted by using N,N-dimethylcyclohexylamine (DMCHA) and recovered by adding CO2, thereby switching DMCHA into a hydrogen carbonate ammonium salt and resulting in the formation of a separate liquid lipid phase

Opportunities for switchable solvents for lipid extraction from wet algal biomass: An energy evaluation

“…It is obvious, however, that these methods are not suitable for industrial production of lipids from microalgae for energy production alone. CO 2 switchable solvents have proven to be able to extract lipid from both dry and wet algae by several researchers now [44,51,52,54]. From the calculation results, it turns out that switchable solvent extraction requires much less energy than the other methods, making it a better candidate when energy applications are considered.…”

“…This work is remarkable, since this was the first time that extraction of lipids from dilute cultivation media without any treatment for cell disruption was reported. The total lipid content expressed on algal dry weight basis obtained through DMCHA extraction of wet samples (50 mg/mL, 24 h extraction) of D. communis, N. gaditana and T. suecica was 29.2 ± 0.9%, 57.9 ± 1.3% and 31.9 ± 1.5% respectively, which was comparable with extraction yields using the B & D lipid extraction method, commonly applied for analytical purpose [52].…”

“…From the few works reported on extracting lipids from algae by switchable solvents [51,52,54], promising results have been obtained with regard to the amount of lipid extracted when compared with traditional analytical extraction methods, such as the B & D method. However, these laboratory results do not elucidate on large scale processes and on potential benefits of using these solvents at large scale still not much is known.…”

“…However, 4-8 wt.% residual amine in extract is still a lot, which indicates that additional recovery operation is needed [54]. Samorì et al used DMCHA for extracting and recovering lipids directly from wet algae samples (about 80% water content) and directly from cultures (biomass concentration around 2 g/L) of three microalgae strains: Nannochloropsis gaditana, Tetraselmis suecica, and Desmodesmus communis [52]. This work is remarkable, since this was the first time that extraction of lipids from dilute cultivation media without any treatment for cell disruption was reported.…”

“…Additional points of attention are the solubility of the solvent in water (which might affect algae cultivation when recycling the untreated water) and the solubility of the solvent in the lipid oil phase. For practical purposes, if a portion of the switchable solvent ends up in the aqueous phase after extraction, this may introduce a significant problem if the aqueous phase would be re-used for growing again algae since many alkyl amines are toxic even at low concentrations [52]. It would also be a problem for the environment if the water is discarded without any further treatment.…”