Recovery of Yam Soluble Protein from Yam Starch Processing Wastewater.

Over the past two decades, many studies have shown that the yam storage protein dioscorin, which is abundant in the wastewater of starch processing, exhibits many biological activities both in vitro and in vivo. In the present study, the acid-precipitation method was optimized using Box-Behnken design (BBD) combined with response surface methodology (RSM) for the recovery of yam soluble protein (YSP) from wastewater. The experimental yield of YSP reached 57.7%. According to relative quantitative proteomics (LC-MS/MS), the crude YSP was mainly composed of 15 dioscorin isoforms, which was further verified by anion-exchange and size-exclusion chromatography. YSP was found to be rich in glutamic acid and aspartic acid, and the eight essential acids made up approximately 33.7% of the YSP. Moreover, the YSP demonstrated antioxidant activity, including scavenging DPPH, hydroxyl and superoxide anion radicals, and the possible structure-activity relationships were discussed. These results indicated that YSP produced by acid precipitation may be used as a protein source with antioxidant properties.

Optimization of the ultrafiltration-assisted extraction of Chinese yam polysaccharide using response surface methodology and its biological activity.

Ultrafiltration is a separation process for purifying and concentrating macromolecular solutions. Using Baiyu yam (Dioscorea opposita Thunb) as the raw material, single-factor experiments, Box-Behnken design (BBD) and response surface methodology (RSM) were employed to investigate the effects of the ultrafiltration pH, temperature and pressure on the extraction rate of Chinese yam polysaccharide (CYP). The constructed regression model is highly significant, and the optimal ultrafiltration-assisted extraction conditions were determined to be the following: pH 6.5, 20 °C and 0.03 MPa. Under these optimal conditions, a CYP extraction rate of 88.7% was achieved. After purification with anion exchange (DE-52) and size-exclusion (Sephadex G-100) columns, the monosaccharide composition of CYP was determined to be 50.8% glucose, 24.2% mannose and 11.8% galactose. Fourier transform infrared (FT-IR) spectroscopy characterization of CYP confirmed the characteristic absorption peaks of the polysaccharides. The microstructure of CYP exhibited characteristics typical of amorphous powders. CYP also exhibited antioxidant activities, including the scavenging of DPPH radicals, hydroxyl radicals and superoxide anion radicals. Moreover, CYP exhibited a relatively strong inhibitory effect on BGC-823 cell growth.