Optimization of ultrasonic alkaline extraction process, structural characterization and functional properties of Euglena protein

Abstract: This paper investigates the extraction rate, structural characterization, and in vitro antioxidant activity of Euglena gracilis polysaccharide (EGP). The extraction rate of EGP was optimized using an ultrasonic alkaline extraction process combined with Plackett-Burman and response surface methodology. Gel permeation chromatography, ion chromatography, Fourier transform infrared spectroscopy, scanning electron microscopy, and free radical scavenging experiments were used to analyze the molecular weight, monosaccharide composition, functional group composition, microstructure, and antioxidant activity of EGP. The optimal process parameters for ultrasonic alkaline extraction of EGP were: a solid-liquid ratio of 1:40 (g:mL), a water bath temperature of 41℃, a water bath time of 0.9 h, a NaOH solution concentration of 1 mol/L, an ultrasonic power of 120 W, and an ultrasonic time of 3 min. Under these conditions, the extraction rate of EGP was (62.84±0.49)%. The results show that EGP is composed of * glucose linked by β-glycosidic bonds, with a molecular weight of 2.13×10⁴ Da. Antioxidant experiments showed that EGP exhibited good antioxidant activity against hydroxyl radicals, DPPH radicals, ABTS cation radicals, and superoxide anion radicals. The structural study of EGP provides a scientific theoretical basis for the continued development and utilization of Euglena.