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.