Publicação
Microalgae Biomass Biorefinery: Development and Implementation of Processing Strategies in an Industrial Unit in Portugal
| Resumo: | The development of sustainable biorefinery strategies for high-value biomolecules from microalgae is essential to promote more efficient and circular resource-use processes. This PhD focused on the extraction, stabilization, and purification of C-phycocyanin (C-PC) from Limnospira platensis, using biphasic systems based on natural deep eutectic solvents (NADES). The work was structured in two parts: the first dedicated to phase behavior studies and process engineering, and the second to the extraction and purification of C-PC from real microalgal biomass, with emphasis on scalability and industrial relevance. In the first part, model aqueous solutions of C-PC were used to screen and optimize NaDES-based biphasic systems. From more than 70 combinations tested, the most effective one achieved high partitioning (Kp = 29.4 ± 0.3) and extraction efficiency (99%), while ensuring phase stability and measurable interfacial tension. Recovery studies demonstrated that back-extraction with a common organic solvent as antisolvent preserved protein integrity. Two recovery routes were tested: (i) membrane pre-concentration, yielding 0.29 ± 0.00 g·L⁻¹ (65.9% recovery), and (ii) centrifugation, which achieved the highest recovery (0.39 ± 0.01 g·L⁻¹) with antioxidant activity of 38.2 ± 2.4%. At the industrial level, membrane pre-concentration may enable continuous operation integrated with centrifugation. Regarding solvent recycling, the most effective solution achieved up to 80% recovery by rotary evaporation, while NaDES required additional treatment for full reuse. The second part addressed the direct extraction of C-PC from L. platensis biomass. Screening of different solvents, including hydrophilic and hydrophobic NADES, revealed that one of tested systems, under optimized conditions, yielded 137.0 ± 8.3 mgC-PC·gdry biomass⁻¹ and significantly improved the color stability of C-PC, with a half-life of 126 days under dark storage at pH 6. Based on these results, new NADES-based biphasic systems were tested and integrated into fast centrifugal partition chromatography (FCPC). From these, one of the most promising systems showed higher selectivity (KC-PC = 1.53 vs. Kchlorophyll = 0.50), producing highly purified fractions (15.9 mgC-PC·L⁻¹, with purity five times higher relative to total proteins and chlorophylls). In contrast, a second system enabled higher C-PC concentrations (up to 615.9 mgC-PC·L⁻¹; purity five and 0.87 times higher relative to total proteins and chlorophylls, respectively), but with lower selectivity. In summary, this thesis demonstrates that NADES allow more selective extraction and more efficient stabilization of C-PC. Furthermore, NADES-based biphasic systems enable effective compound separation, providing products of different purity grades depending on the final application, as well as scalable and sustainable strategies for microalgal biorefineries. |
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| Autores principais: | Pereira, Bruno Alexandre das Neves |
| Assunto: | C-phycocyanin natural deep eutectic solvent biphasic systems microalgae biorefinery Limnospira platensis sustainable processing photostability |
| Ano: | 2025 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso embargado |
| Instituição associada: | Universidade Nova de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório Institucional da UNL |
| Resumo: | The development of sustainable biorefinery strategies for high-value biomolecules from microalgae is essential to promote more efficient and circular resource-use processes. This PhD focused on the extraction, stabilization, and purification of C-phycocyanin (C-PC) from Limnospira platensis, using biphasic systems based on natural deep eutectic solvents (NADES). The work was structured in two parts: the first dedicated to phase behavior studies and process engineering, and the second to the extraction and purification of C-PC from real microalgal biomass, with emphasis on scalability and industrial relevance. In the first part, model aqueous solutions of C-PC were used to screen and optimize NaDES-based biphasic systems. From more than 70 combinations tested, the most effective one achieved high partitioning (Kp = 29.4 ± 0.3) and extraction efficiency (99%), while ensuring phase stability and measurable interfacial tension. Recovery studies demonstrated that back-extraction with a common organic solvent as antisolvent preserved protein integrity. Two recovery routes were tested: (i) membrane pre-concentration, yielding 0.29 ± 0.00 g·L⁻¹ (65.9% recovery), and (ii) centrifugation, which achieved the highest recovery (0.39 ± 0.01 g·L⁻¹) with antioxidant activity of 38.2 ± 2.4%. At the industrial level, membrane pre-concentration may enable continuous operation integrated with centrifugation. Regarding solvent recycling, the most effective solution achieved up to 80% recovery by rotary evaporation, while NaDES required additional treatment for full reuse. The second part addressed the direct extraction of C-PC from L. platensis biomass. Screening of different solvents, including hydrophilic and hydrophobic NADES, revealed that one of tested systems, under optimized conditions, yielded 137.0 ± 8.3 mgC-PC·gdry biomass⁻¹ and significantly improved the color stability of C-PC, with a half-life of 126 days under dark storage at pH 6. Based on these results, new NADES-based biphasic systems were tested and integrated into fast centrifugal partition chromatography (FCPC). From these, one of the most promising systems showed higher selectivity (KC-PC = 1.53 vs. Kchlorophyll = 0.50), producing highly purified fractions (15.9 mgC-PC·L⁻¹, with purity five times higher relative to total proteins and chlorophylls). In contrast, a second system enabled higher C-PC concentrations (up to 615.9 mgC-PC·L⁻¹; purity five and 0.87 times higher relative to total proteins and chlorophylls, respectively), but with lower selectivity. In summary, this thesis demonstrates that NADES allow more selective extraction and more efficient stabilization of C-PC. Furthermore, NADES-based biphasic systems enable effective compound separation, providing products of different purity grades depending on the final application, as well as scalable and sustainable strategies for microalgal biorefineries. |
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