Extraction by supercritical fluids of value-added compounds from microalgae grown in photobioreactors simulating different climatic conditions

Abstract

Resumen del trabajo presentado al 17th European Meeting on Supercritical Fluids y al 7th European Meeting on High Pressure Technology, celebrados en Ciudad Real (España) del 8 al 11 de abril de 2019.[Introduction]: Microalgae cultivation is strongly dependent on the daylight availability. Under natural climatic conditions, the light intensity, the photoperiod and the temperature play a key role in increasing the performance of microalgal-based processes. Globally, the market for microalgae-based products has gained a lot of attention in recent years because of the potential of these microorganisms to produce high-value bioproducts, like pigments, omega-3 fatty acids, proteins and carbohydrates which may be used in several food, pharma and cosmetic applications. Although there is such a market, the advance of microalgal biotechnology to a medium-sized market requires studies on the optimization of the industrial scale, due to the high costs for the extraction of biocompounds of interest. In this regard, there is a need to combine appropriate, selective, costeffective, and environmentally friendly extraction procedures with the legal requirements regarding the use of food-grade solvents and processes. Recently, there has been an increasing interest in the use of supercritical fluid extraction (SFE) with carbon dioxide (CO2) as a solvent. Carbon dioxide is an ideal solvent for the extraction of natural products because it is non-toxic, non-explosive, readily available and easy to remove from extracted products. In this sense, the objective of this work was to evaluate the influence of climatic conditions on the production of high-value biocompounds and their selective extraction from the biomass through a compressed fluids’ platform; the microalga Scenedesmus obliquus has been employed as case study.[Results and discussion]: The biomass of Scenedesmus obliquus was grown under different conditions in photobioreactors, simulating diverse climatic conditions in Brazil (tropical, subtropical, tropical Atlantic and equatorial) in four extreme regions (Boa Vista-RR, Rio Grande-RS, João Pessoa-PB and Rio Branco-AC). The different biomasses have been subjected to sequential extractions in order to achieve extracts enriched in target biomolecules. A compressed fluids’ platform has been employed considering different steps such as supercritical fuid extraction with pure carbon dioxide, SFE with carbon dioxide plus a polar modifier (ethanol), gas expanded liquids and pressurized liquid extraction. Final extracts’ composition has been determined by high performance liquid chromatography coupled to evaporative light-scattering detector (HPLC-ELSD) and HPLC coupled to diode array and mass spectrometry detectors (HPLC-DAD-MS/MS).[Conclusions]: Significant variation of climates by geographic location in the production of high-value bioproducts is an important tool in the planning and implementation of future microalgae-based cropping projects based on available climatic resources anywhere in the world