Optimization of Protein Extraction from Duckweed Using Different Extraction Processes

Abstract Despite its recent commercialization of duckweed, the extraction of high-quality protein presents challenges primarily in the efficiency of the extraction processes. In this study, conventional, ultrasound-assisted extraction (UAE), and ultrafiltration (UF) extraction techniques, were evaluated showing significant enhancements in protein yield, amino acid profile, and chlorophyll extraction. The highest protein release of 80.83% was achieved with a 40% amplitude applied for 10 min. UAE increased the protein yield substantially compared to conventional methods, achieving the highest yield of 41.30% with a moderate protein content of 50.91% in Lemna gibba protein concentrate. However, it comes at the cost of reduced protein purity and altered protein profiles due to co-extraction of other plant components. SDS-PAGE analysis revealed that ultrasound methods improved the extraction of chlorophyll-binding proteins (LHCB1) but decreased the efficiency of extracting RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) subunits compared to non-ultrasound methods. Lysine and tryptophan were identified as limiting essential amino acids (EAA), except when ultrasound methods were applied, which raised the levels partially above the recommended amino acid score (AAS) threshold of 1 for adults. The study established a nitrogen-to-protein conversion factor for duckweed at ~ 5.8, aligning with RuBisCO-based calculations and providing a more accurate tool for future nutritional assessments of duckweed proteins.

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