Ultrasound-assisted extraction enhances functional properties and in vitro digestibility of Pleurotus eryngii mycelium protein: The role of structural unfolding.

Abstract

To valorize Pleurotus eryngii mycelium protein (PeMP) as a sustainable protein source, this study investigated the efficacy of ultrasound-assisted extraction (0-450 W) in simultaneously enhancing the extraction yield and modulating the physicochemical properties of PeMP. Results showed that ultrasound treatment at 150 W achieved a maximal extraction yield of 76.23%, significantly outperforming the alkali-soluble acid precipitation method. Structural characterization, including SDS-PAGE and LC-MS/MS, revealed that ultrasonic cavitation induced controlled protein unfolding without disrupting the primary peptide chain. This process reduced the content of rigid α-helices and significantly increased surface hydrophobicity. These conformational changes markedly improved the interfacial behavior of PeMP: appropriately ultrasound-modified (150 and 300 W) fractions exhibited superior solubility, emulsifying activity, and foaming stability compared to commercial soy protein isolate (SPI), while maintaining comparable water- and oil-holding capacities. Although the essential amino acid ratio was slightly lower than that of SPI, it fully met the FAO/WHO requirements for adult nutrition. Furthermore, the structural loosening exposed enzyme cleavage sites, leading to a significant enhancement in vitro digestibility. Overall, this study demonstrates that ultrasound-assisted extraction acts as a robust dual-function strategy for producing high-quality mycelium protein with tailored functionalities, offering a viable plant-based alternative for the food industry.