Electric Pulse-lnduced lntracellular Changes in Microalgae: Chloroplasts as a Window into Cellular Response

Protein extraction from Chlorella vulgaris using Pulsed Electric Fields (PEF) requires a critical post-treatment incubation step to achieve high yields-up to 50°/o of the total protein content. This protein release is primarily driven by enzymatic autolysis, which is triggered by cell death following PEF exposure. In contrast, the extraction of neutral lipids from microalgae such as Auxenochlorella protothecoides primarily depends on the energy input during PEF _treatment. In this case, lipid recovery via solvent extraction .follows a dose-dependent response. In this study, we demonstrate that chloroplast integrity serves as a sensitive indicator of PEF-induced, dose-dependent intracellular damage. Microscopic observations revealed the release of chlorophyll from disrupted chloroplasts following treatment. Additionally, an immediate increase in chlorophyll fluorescence intensity following PEF exposure suggests that energy transfer processes within photosystems I and 11-located in the thylakoid membranes-are impaired. This damage intensifies during the incubation period, indicating that autolysis further contributes to cellular disruption. ... mehrThese findings show that PEF treatment compromises both chloroplast and thylakoid membranes, leading to chlorophyll release in a dose-and time-dependent manner. Alterations in chloroplast structure thus provide valuable insight into the extent and dynamics of PEF-induced cellular stress in microalgae. Furthermore, a correlation between chloroplast damage and so.lvent extraction 􀀔 efficiency could be identified. This knowledge enables identification of an 'extraction-ready' cell state following pre-treatment and incubation, which can be used to optimize the extraction process and enhance overall efficiency.