Aurino, Elena (2026) DESIGN OF SUSTAINABLE PROCESSES FOR MICROALGAL METABOLITE RECOVERY. [Tesi di dottorato]

	Documento PDF Elena_Aurino_38_COMPLETO.pdf Visibile a [TBR] Amministratori dell'archivio Download (2MB) | Richiedi una copia
	Documento PDF Elena_Aurino_38_PARZIALE.pdf Visibile a [TBR] Amministratori dell'archivio Download (627kB) | Richiedi una copia

Abstract

Microalgae are versatile and sustainable feedstocks for biorefineries, offering the potential to produce a wide portfolio of high-value metabolites without competing for arable land or freshwater resources. Their ability to adapt to extreme conditions and to synthesize bioactive compounds - such as proteins, pigments, fatty acids, and antioxidants - makes them attractive for applications in food, pharmaceuticals, cosmetics, and biofuels. However, the structural complexity and variability of microalgal cell walls pose significant challenges for efficient extraction, requiring tailored disruption strategies that preserve thermolabile compounds while ensuring scalability and economic viability. The present PhD thesis addresses the recalled challenges through two complementary paths focused on hydrophilic and hydrophobic metabolite recovery. The first path regards the investigation of bead-beating as a mechanical disruption technique for extracting phycobiliproteins (PBPs) and other water-soluble metabolites from the extremophile Galdieria sulphuraria. A preliminary comparative strain screening revealed that G. sulphuraria is superior to Arthrospira platensis in terms of PBP yield and thermostability. Key operating conditions - including pH, biomass storage conditions, and solid–liquid separation - were optimized to maximize metabolite yield and biointegrity. Kinetic studies revealed hyperbolic release profiles for PBPs, proteins, and carbohydrates, with maximum recovery achieved within eight minutes. Models were: i) proposed to correlate both the maximum recovery and initial release rate with the biomass-to-bead ratio; and ii) experimentally validated, providing a robust framework for process design and scale-up. The second path explores a mild microwave-assisted biphasic extraction (MABE) process for the co-recovery of docosahexaenoic acid (DHA), fucoxanthin, and proteins from Tisochrysis lutea - a strain lacking a rigid cell wall - was investigated. A green solvent, 2-methyltetrahydrofuran (2-MeTHF), was combined with water to create a biphasic system that aligned with green chemistry principles. Preliminary screening experiments provided 35 °C as the upper safe temperature for DHA preservation and highlighted the protective role of water during conventional heating. Under microwave conditions, the control of energy input per cycle enabled mild operating temperatures, while a multicycle strategy enhanced mass transfer without compromising metabolite stability. Extraction was subsequently optimized using Response Surface Methodology (RSM), considering microwave power, number of cycles, solvent ratio, and biomass state. The proposed models under the assessed parameters were validated experimentally, confirming the feasibility of simultaneous recovery of proteins, fatty acids, DHA, and fucoxanthin with minimal degradation. Overall, the PhD thesis proposes an integrated methodological framework for designing sustainable and scalable microalgal biorefineries that couple efficient cell disruption with stringent thermal control and the use of eco-compatible solvents. The experimental evidence and proposed predictive models provide valuable tools for the development and industrial implementation of innovative extraction processes, contributing to the transition towards a circular bioeconomy based on microalgal biomass exploitation/valorisation.

Downloads

Actions (login required)

Modifica documento