Optimisation of the lipid extraction of fresh black soldier fly larvae (Hermetia illucens) with 2-methyltetrahydrofuran by response surface methodology

Abstract

While black soldier fly larvae (BSFL, Hermetia illucens) have the potential to become a renewable, industrial feedstock; lipid extractions are typically performed with hexane. Green solvents, however, are gaining more popularity to replace these harmful solvents such as hexane. In this study, the green solvent 2-methyltetrahydrofuran (2-MeTHF) was compared with hexane for extracting lipids from fresh BSFL at moderate temperature. Response surface methodology was used to investigate these wet extractions with a Soxhlet extraction as benchmark. Two sets of optimal process settings were predicted and validated for (1) maximising solvent efficiency and (2) maximising lipid recovery. The resulting extracts were characterised by their fatty acid profile and lipid class composition. The results of the benchmark extraction (Soxhlet) showed that 2-MeTHF could extract significantly more lipids from dried BSFL than hexane (43.23 vs. 40.34 g lipids/100 g DM). No significant difference was found between the maximum solvent efficiencies of hexane and 2-MeTHF. By performing the wet extraction with 2-MeTHF at 45 °C with 15 w/w % fresh BSFL, 40 w/w % 2-MeTHF, and 45 w/w % water; the highest lipid recovery was obtained (94.9 ± 1.8 % of total BSFL lipids). These results indicated that the wet extraction was able to extract a similar amount of lipids compared to the Soxhlet extraction. Although the fatty acid profiles did not differ between extraction conditions, 2-MeTHF extracted a higher quantity of free fatty acids and valuable phospholipids compared to hexane. Consequently, the wet lipid extraction with 2-MeTHF can be considered a suitable, more ecologic alternative for the conventional extraction of dried BSFL with hexane.

Valorization of spent coffee grounds by 2-methyloxolane as bio-based solvent extraction. Viable pathway towards bioeconomy for lipids and biomaterials

“…Nevertheless, the 4.45% of fatty acids present in the lipid fraction could have originated during the intended use of coffee powder or perhaps while drying the material before oil extraction. These results are in line with earlier findings where lipid extraction with 2-MeOx in dry and aqueous mode lead to hydrolysis of TAG into FFA, DAG, MAG (Ravi et al, 2019;Gharby et al, 2020;Smets et al, 2021). This phenomenon can be attributed to the water affinity displayed by 2-MeOx.…”

On the nitrogen content and a robust nitrogen-to-protein conversion factor of black soldier fly larvae (Hermetia illucens)

“…Besides being rich in lipids (30 -40 %), these larvae also contain high amounts of proteins (20 -50 %) and chitin (4 -7 %), all expressed on dry matter (5)(6)(7)(8). In addition, BSF proteins contain all essential and limiting amino acids for poultry and pigs (i.e., in order of limitation: Lys, Arg, Thr, Met, Cys, Trp, Ile, Leu, Val, His, Phe, and Tyr), and salmon (i.e., in order of limitation: His, Ile, Leu, Lys, Met, Phe, Thr, Val, Arg), among others, in sufficiently high quantities (9,10).…”

“…Regardless whether BSF larvae are incorporated directly into human food (3), used as animal feed (10), or processed into feedstock for industrial applications (5); accurate quantification of their chemical composition (i.e., lipids, protein, and chitin) is of utmost importance. At this moment, a broad discussion exists in the literature on the subject of insect protein analysis.…”

Novel Insights on the Sustainable Wet Mode Fractionation of Black Soldier Fly Larvae (Hermetia illucens) into Lipids, Proteins and Chitin

“…Freezing of larvae without any thermal pretreatment results in lipolysis wherein TAG are hydrolysed into FFA, DAG and MAG. A recent study on the wet extraction of lipids from fresh BSFL with 2-methyl tetrahydrofuran as solvent was proposed [29]. The study, too, found similar traits where TAG hydrolysis could not be avoided, even with solvent extraction in a wet phase.…”

“…In our previous study, we discussed the potentiality of 2-methyl tetrahydrofuran replacing hexane for the delipidification of BSFL. Alternative biobased solvents such as 2-methyl tetrahydrofuran, ethanol and ethyl acetate seem to be potential alternatives for conventional solvents [28][29][30][31]. Yet, several practical challenges exist for the industrial-scale implementation of such solvents, namely cost of solvent, energy requirement, infrastructure availability, scientific data of solvent and its interaction with biomass.…”