Single-step disruption and protein recovery from Chlorella vulgaris using ultrasonication and ionic liquid buffer aqueous solutions as extractive solvents

Microalgae are natural renewable sources providing attractive high-value products such as proteins. Due to the high costs incurred during drying processes, wet extraction from fresh microalgae biomass can be a promising approach. In this work, a single process step integrating cell disruption and protein recovery from wet Chlorella vulgaris by using ultrasonication and aqueous solutions of ionic liquids (ILs) as extractive solvents was proposed. The ILs assessed belong to the group of Good's buffer ionic liquids (GBILs), and were prepared by a combination of Good's buffer-based anions, namely 2-hydroxy-3-morpholinopropanesulfonate and 2-[bis(2-hydroxyethyl)amino]ethanesulfonate, and tetrabutylammonium, tetrabutylphosphonium and cholinium cations. These GBILs possess high biocompatibility and buffering capacity at neutral pH region. The protein recovery capabilities of the aqueous solutions of GBILs were compared with conventional buffers, using the same cell disruption approach. After the proper selection of the buffer solution with higher capability to extract microalgal proteins, alternative disruption techniques such as freeze-thaw, non-ionic detergent-based lysis using Triton X-100 and the combined methods were studied. The most efficient strategy, namely ultrasonication-assisted extraction, was further investigated for the effects of the process variables such as the buffer concentration, the addition of NaCl, the biomass concentration, and the ultrasonic time and power.