Microwave-assisted aqueous two-phase extraction of diverse polysaccharides from Lentinus edodes: Process...

Microwave-assisted aqueous two-phase extraction (MAATPE) was applied to simultaneous extraction of diverse polysaccharides from Lentinus edodes with aqueous two-phase extraction system (ATPS) of ethanol/ammonium sulfate as the biphasic extractant. Key factors in MAATPE process were optimized by response surface methodology, and the optimum conditions were concluded as follows: the ATPS composition of ethanol concentration 26.0% (w/w) and (NH₄)₂SO₄ concentration 19.58% (w/w), extraction temperature 78.7 °C, extraction time 19.55 min and solid-to-solvent ratio 1:50. The extraction yields of the polysaccharides from the top phase (PTP) and the bottom phase (PBP) were 2.12 ± 0.21% and 11.16 ± 0.28%, respectively. By means of FT-IR, HPGPC and HPLC analysis, PTP and PBP were different from each other in chemical structure, their average molecular weight (M_W) were respectively 119,533 Da and 3906 Da. Also, the mechanism of MAATPE process was explored by composition analysis and scanning electron microscopy. Both polysaccharides exhibited stronger antioxidant activities, EC₅₀ values of scavenging DPPH, hydroxyl and superoxide radicals for PBP achieved 580 ± 3, 83.1 ± 3.6 and 91.1 ± 0.5 μg/mL as against 560 ± 4, 76.3 ± 2.2 and 89.3 ± 2.4 μg/mL of PTP, respectively. Compared with conventional methods using a mono-phase solvent, MAATPE can not only greatly improve extraction efficiency, but also selectively extract diverse polysaccharides.