Rapid Accumulation of Astaxanthin in Haematococcus pluvialis Induced by Mild Hydrostatic Pressure

Hydrostatic pressure is a key environmental factor affecting the morphology and metabolism of aquatic organisms. This study investigated the technical feasibility of a pressure-based stress method for inducing astaxanthin (AXT) biosynthesis in Haematococcus pluvialis at 5–30 bar for 24 h. The AXT content of algal cells pressurized at an optimal pressure of 10 bar for 2 h was 23.6% and 18.2% higher than that of the initial cells and untreated controls, respectively. The contents of major AXT intermediates, such as β-carotene, zeaxanthin, and canthaxanthin, were also increased by this pressurization. However, prolonged and excessive pressurization (especially at 20–30 bar) caused considerable morphological changes, such as secretion of extracellular biomaterials and separation of the cell wall and cytoplasm, resulting in a high cell damage rate of approximately 41.3%. Thus, pressurization, if properly applied, can be a simple and effective stress strategy for inducing target ketocarotenoid compounds.