Fractionation of Squid Pens with Ionic Liquids – An upgraded β-Chitin and Shellfish Protein Production

In this work, the foundation of a biobased ionic liquid utilization of squid waste has been scrutinized. An ionic liquid screening showed that the biocompatible ionic liquid choline acetate, [Ch][OAc], can extract more than 80 wt% of the protein and precipitate it upon solvent swing between ethanol and water. Process parameter optimization was carried out with factorial design of experiments to yield 75% of recovered protein with an estimated 90% purity and a highly acetylated, crystalline β-chitin with up to 95% purity. Physico-chemical analyses of these two streams confirmed the efficiency of ionic liquid separation and the amino acid profiling of the protein isolate revealed the presence of three major essential amino acids, histidine, leucine and valine that could be a valuable alternative protein source for feed in aquaculture. Molecular dynamic simulations show that the affinity of [OAc]- to protein surfaces is greater than that of alternative anions, facilitating protein solubilization. However, its combination with [Ch]+ is optimal because the interactions of this cation with the protein surface are relatively weak, allowing the protein to be recovered from the IL. A material mass balance of the process has shown the solvent usage is high, which ultimately impacts on high energetic requirements. Techno-economic confirmed that solvent usage makes up to nearly 65% of the minimum selling price of the protein, which reaches up to 9 $/kg, but decreases with co-production of β-chitin down to 0.6 $·kg-1 for each 1 $·kg-1 of chitin. Solvent usage also impacts negatively on CO2 emissions with up to 4.27 kg CO2·kg-1 of product. These emissions are split into 61% for the protein and 39% for the β-chitin production.