Sequential enzymatic and ultrasonic extraction of lentinula edodes mushroom proteins leading to enhanced yield and significant immunoactivity

Abstract

Lentinula edodes is a widely consumed edible fungus and a rich source of proteins with both nutritional and medicinal value. This study was to identify the most effective process for extraction of proteins from L. edodes mushroom by comparison of water extraction (WE), enzyme-assisted extraction (EAE), ultrasound-assisted extraction (UAE), and various combinations of EAE with UAE, EAE followed by UAE (EUE), UAE followed by EAE (UEE), and simultaneous EAE and UAE (SEUE). The two-step sequential scheme of EAE followed by UAE, designated as EUE, resulted in the highest protein yield compared to the UEE and SEUE extraction methods. The soluble protein yield by EUE (9.4%) was nearly three times that by UEE (3.6%) and around two times higher than by EAE (4.9%), respectively. Compared with other extraction methods, the protein fraction by EUE had the highest protein content (56.0%) and β-sheet content (55.8%) and exhibited the strongest in vitro immunostimulatory activity. Through statistically designed experiments and response surface methodology, EUE conditions were optimized as enzyme 0.28% (w/v), ultrasound amplitude 62%, and (NH4)2SO4 saturation 69%, achieving 9.7% protein yield and 58.4% protein content. The distribution of protein molecular weights was below 10 kDa and between 25–75 kDa. The protein fraction contained nutritional amino acids and showed significant immunostimulatory activities in vitro. EUE has shown promising potential for efficient extraction of proteins from mushrooms in the food industry.