High-pressure disruption for efficient protein extraction from Chlorella pyrenoidosa: comparative insights with conventional methods

Chlorella pyrenoidosa is a protein-rich microalga (> 40% dry weight), and its protein extraction is challenging due to its multilayered cell wall. In this study, the protein extraction efficiency and structural disruption of high-pressure disruption (HPD), alkaline, ultrasonication, and enzymatic methods were compared. At 40 kpsi, HPD achieved 88% protein yield—outperforming alkaline (70%), ultrasonication (64%), and enzymatic (34%) methods, without evident low-molecular-weight fragmentation (based on SDS-PAGE), and maintaining a biological value of 70.1. Instantaneous pressurization fragmented cells into 0.1–10 μm particles, releasing both intracellular proteins and cell wall components. Monosaccharide analysis indicated the concurrent release of structural sugars, with HPD extracts containing 191 g·kg −1 total monosaccharides (4× aqueous extracts), including cell wall-specific muramic acid (14.7 g·kg −1 ) and N -acetylglucosamine (18.4 g·kg −1 ), alongside intracellular glucose and galactose. These findings are consistent with extensive physical disruption of the multilayered cell wall and enhanced intracellular protein release. In contrast, alkaline treatment degraded the outer sheath ( N -acetylglucosamine: 17.4 g·kg −1 ) but resulted in protein aggregation, while ultrasonication created surface pores and released protein content. Enzymatic methods (e.g., Viscozyme® L) selectively hydrolyzed surface polysaccharides without penetrating deeper layers. Scanning electron microscopy and particle size analysis confirmed extensive structural disintegration after HPD treatment. Overall, these results demonstrate the effectiveness of HPD under the tested conditions for promoting protein extraction from C. pyrenoidosa . The potential integration of mechanical disruption and enzymatic hydrolysis warrants further investigation to evaluate possible complementary effects and process efficiency.