Pulsed electric field-assisted extraction of pigments from chlorella vulgaris

Abstract

Chlorella vulgaris is a microalga that represents a rich source of valuable compounds like the carotenoid lutein. Exploiting this microalga as a feedstock presents several advantages compared to traditional crops. However, there are still several obstacles to fully take advantage of microalgae metabolites such as the ability to successfully extract these compounds from the cell biomass at low operation cost. The implementation of pulsed electric fields (PEF) to improve the recovery of microalgae bioproducts with low energy requirements could help to make them a feasible feedstock. This chapter aims to describe the optimization of PEF technology in terms of electric field strength, treatment time, and temperature in order to get the best results in terms of lutein extraction yield with the lower energy input. Applying either pulses of milliseconds (5 kV/cm-40 ms) or microseconds (20 kV/cm-75 μs) improved the extraction of carotenoids from C. vulgaris cells by 80%. However, to obtain similar yields, treatments applied with microsecond pulses were more energetically favorable (30 kJ/kg) than treatments applied with millisecond pulses (150 kJ/kg). Besides electric field strength and treatment time, temperature is another critical parameter affecting the efficacy of the PEF treatment. Increasing the PEF processing temperature led to an improvement on lutein extraction. However, although significant increments in lutein extraction were observed when treatment temperature increased from 10°C to 30°C, temperatures above 30 C hardly improved the lutein extraction yield. Therefore, since the cultivation temperature of this microalgae between 25°C and 30°C and the higher efficiency of microsecond pulse protocols obtained, a treatment of 25 kV/cm-100 μs (62 KJ/kg) at 25-30 ° C results in the most suitable PEF treatment conditions increasing the extraction yield around 3.5-4.2-fold in comparison with the control.