Feasibility study on the extraction of lutein from the green alga Chlamydomonas asymmetrica.
A research project by Weihenstephan-Triesdorf University of Applied Sciences and the University of Applied Sciences Amberg-Weiden
The demand for natural and sustainably produced food additives is constantly increasing due to rising demand and changing consumer awareness. The xanthophyll lutein is one of the food additives that are also marketed as ingredients in dietary supplements due to their health-promoting effects. In the food industry, lutein is mainly used as a colorant and antioxidant (E 161 b, GRAS status). Currently, most of the lutein produced comes from the upright marigold Tagetes erecta. Microalgae represent another natural source as a potential alternative. The literature even describes three to six times higher lutein production in algae than in Tagetes erecta, taking into account the rapid biomass growth of algae.
Algae cultivation in bubble column photobioreactors
As part of the project, the extraction of lutein-containing extracts from the microalgae Chlamydomonas asymmetrica was comprehensively investigated. The two project partners worked on complementary areas of focus. OTH Amberg-Weiden focused on cultivating the algae in bubble column photobioreactors to produce a suitable biomass base. Stable and reproducible cultivation methods were developed, which were carried out on various scales (7.5 L and 15 L) and evaluated using an adapted growth model. Space-time yields of up to 0.6 g L⁻¹ d⁻¹ were achieved. The highest specific lutein contents occurred in early culture phases, reaching up to 5.3 mg g⁻¹. Various mechanical and thermal solid-liquid separation processes were tested for biomass processing, with centrifugal processes achieving separation efficiencies of up to 99.6%. Filtration processes proved unsuitable due to the high EPS (extracellular polymeric substances) content of the algae. Studies on cell disruption using pulsed electric fields (PEF) showed no significant influence on lutein yield.
HSWT Freising focused on the extraction and purification of lutein from the algae biomass provided by OTH. To this end, extractions with ethanol were carried out and optimized by varying the extraction parameters (solvent, time, temperature, biomass content). The optimal conditions were found to be ethanol at 1.5% biomass content, 40 minutes, and room temperature. Extractions with supercritical CO₂ proved to be practicable only in the presence of ethanol as a co-solvent, but primarily resulted in lipid-rich and lutein-poor extracts. Adsorption and column chromatography separations allowed lutein fractions to be obtained in near-pure form and their spectroscopic identity to be confirmed. In addition, the antioxidant properties of the extracts were demonstrated, with lipid fractions in particular showing pro-oxidative effects.
The project has thus successfully investigated the entire process chain from cultivation and processing to extraction and purification of lutein from C. asymmetrica , thereby laying important foundations for subsequent process scaling and industrial use.
Weihenstephan-Triesdorf University of Applied Sciences, Faculty of Bioengineering
Project management: Prof. Sabine Grüner-Lempart, Ph.D., Jörg Schäffer, Ph.D.
East Bavarian University of Applied Sciences Amberg-Weiden, Faculty of Mechanical Engineering/Environmental Technology
Project management: Prof. Dr.-Ing. Christoph Lindenberger, Natalie Leitenberger
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Final report "Feasibility study on the extraction of lutein from the green alga Chlamydomonas asymmetrica"