Development of Protocols for the Extraction, Separation and Characterization of Lipids - Determination of photosynthetic Lipid Composition under different Light Environments in the Microalga Nannochloropsis oceanica

摘要

The main aim of this research was to develop protocols and techniques for simultaneous extraction, separation and characterization of photosynthetic lipids synthesized in Nannochloropsis oceanica. The lipid composition can be changed by changing the environmental conditions of the alga, inducing an alteration of components of the photosynthetic machinery. To understand the mechanisms involved in Nannochloropsis in response to changing environmental conditions, the characterization of the photosynthetic lipid composition is a crucial and challenging task. Therefore, the secondary objective of this master project was thus to apply the developed methods for extraction, separation and characterization to investigate the effects of high irradiance on the composition of photosynthetic lipids in Nannochloropsis oceanica. Both chromatographic and mass spectrometric techniques were used for this purpose. A particular focus has also been directed toward the investigation of non-photochemical quenching, namely the utilization of the xanthophyll cycle and state transitions during high light. Although state transitions have been widely observed in higher plants, eukaryotic algae and cyanobacteria, the presence of this process have so far not been confirmed for Nannochloropsis. The key mechanism of state transitions is based on a flexible binding of antennae complexes to PSII, allowing dissociation of LHCs from PSII in response to over-excitation, in order to prevent photo damage. Spectroscopic techniques have revealed a weak binding between the antennae complexes and PSII, indicating that in addition to having an active xanthophyll cycle, Nannochloropsis also may employ state transitions.