Microwave-Assisted DES Extraction Enhances Functional Properties, In Vitro Digestibility and Bioactivities of Auxenochlorella Protein and Its Digests.

Microalgal proteins are emerging as sustainable alternatives to conventional protein sources, but recalcitrant cell walls hinder their efficient and green extraction. The effects of microwave-assisted deep eutectic solvent (DES) extraction (MADE) on functional properties and biological activities of Auxenochlorella pyrenoidosa proteins (CPPs) were evaluated in comparison with conventional DES extraction and water bath-assisted DES extraction (WADE). Compared with conventional DES extraction, both MADE and WADE significantly improved the extraction efficiency, solubility, foaming capacity, and emulsifying activity of CPPs, as well as the biological activities of their digests (p < 0.05). Notably, MADE-treated CPPs exhibited superior performance, compared with WADE-treated CPPs across all evaluated properties at identical extraction times ranging from 30 to 120 min. MADE enhanced the extraction efficiency of CPPs by 15.20% and 10.86% relative to WADE at 60 and 90 min, respectively. SDS-PAGE analysis revealed that both MADE- and WADE-treated CPPs showed protein bands corresponding to molecular weights of approximately 190 and 54 kDa, along with a low-molecular-weight fraction below 10 kDa. Principal component analysis combined with heatmap analysis showed that MADE at 120 min yielded the optimal CPPs with the best functional properties and biological activities. These results highlight the potential of CPPs as multifunctional ingredients for functional food and nutraceutical applications. PRACTICAL APPLICATIONS: This study shows that MADE is a fast, efficient method for protein recovery from the microalga Auxenochlorella pyrenoidosa, yielding more than twice as much protein as conventional DES extraction. Because the recovered protein exhibits good foaming and emulsifying properties and its digestion products remain bioactive, these CPPs offer food manufacturers a sustainable, algae-based ingredient and a source of bioactive compounds for application in beverages, baked goods, dairy alternatives, dressings, and functional foods.