New method for the comprehensive recovery of all biochemical components from sweet potato wastewater in starch production\

A new and simple method was developed and optimized for comprehensive recovery of all soluble biochemical components from sweet potato wastewater of starch factory. The wastewater was adjusted to pH 3.8 to precipitate crude polyphenol oxidase (PPO), followed by ultrafiltration to get crude beta-amylase and nanofiltration to recover small molecular organic compounds. The crude PPO and beta-amylase can be used directly in food and other industries, or were precipitated by 50% ethanol to make two purified enzymes and sweet potato storage proteins (sporamins). Through this simple procedure, 3.2 g PPO (with 1.2 X 105 U/g and a recovery rate of 38.7%), 1.2 g beta-amylase (with 3.4 X 107 U/g and a recovery rate of 97.5%), 13.6 g storage proteins and 7.2 g small molecule organics were obtained from the wastewater of one kilogram of sweet potato. The recovered products have high economic values and wide application in industries. This work provides a practical approach for comprehensive utilization of sweet potato resource and has significant economic and environment benefits in agricultural and food industries.