Chapter 7 - Emerging technologies for the clean recovery of antioxidants from microalgae

Abstract

Microalgae are evaluated as a prosperous and sustainable source of natural bioactive compounds with therapeutic properties. They include fatty acids, chlorophylls, carotenoids, phycobiliproteins, polyphenols, and vitamins, which have a commercial relevance for the potential applications as natural additives or active ingredients in food, feed, cosmetic, and pharmaceutical products. Conventional extraction of these high-value compounds from microalgae is traditionally conducted via organic or aqueous solvents following the dry or wet route. However, these methods are time-consuming and require large amounts of solvent, relatively high temperature that may cause loss of valuable compounds, and may lead to low extraction yields and selectivity (purity). In light of these drawbacks, the challenge is the development of more sustainable, environment-friendly extracting technologies enabling high recovery yields and selectivity with reduced operative costs. This chapter provides an overview of the microalgae-derived compounds with potential therapeutic properties and details the most advanced extraction techniques for the future microalgae biorefinery. To this end, the chapter first covers the simple steps of the biorefinery process of microalgae that integrate different technologies for the sustainable recovery of a gamut of valuable compounds with suitable quality and sufficient quantities. Later, the chapter extensively details the conventional and emerging extraction technologies based on the use of electrotechnologies (pulsed electric fields, moderate fields, and high voltage electric discharges), liquid pressurization, supercritical fluids, microwaves, ultrasounds, as well as high-pressure homogenization, highlighting advantages and drawbacks concerning their potential for the future microalgae biorefinery. The general discussion includes the detailed analysis of the extraction efficiency of these technologies, when used alone or in a hurdle or cascade approach, in terms of recovery yield of target biomolecules with antioxidant properties and purity (selectivity) of the extracts.