Subcritical water extraction and beta-glucosidase-catalyzed hydrolysis of quercetin glycosides in onion waste

摘要: Onion waste is a renewable raw material, rich in different molecular species of the antioxidant quercetin. To utilize this resource, an environmentally sustainable procedure has been developed, using pressurized hot water to extract quercetin species, followed by biocatalytic conversion glycosides and carbohydrates. Two recombinantly expressed thermostable β-glucosidases, Thermotoga neapolitana β-glucosidase A B, were utilized as catalysts. These enzymes maintain activity at temperatures around 90 °C, are therefore ideal use combination with extraction. Our results, based on experimental design, showed that they converted active less than 10 min reaction time pH 5.0. Experimental design optimal extraction conditions included three 5 cycles 120 °C 50 bars, giving total 15 min. Several types isorhamnetin well kaempferol detected onion LC-MS/MS analysis. After converting glycosidic compounds their respective aglycones, content was mg g−1 dry weight (RSD 8%). In summary, our research demonstrates subcritical β-glucosidase-catalyzed hydrolysis rapid method determine samples, it only uses solvent