Isolation and Purification of Anthocyanins from Black Bean Wastewater Using Macroporous Resins

Isolation and purification of anthocyanins from black bean canning wastewater by column chromatography with macroporous resins were investigated in this study. Different adsorption materials and adsorption conditions were compared and the most effective material and adsorption conditions were selected to purify anthocyanins. Purified anthocyanins then were identified by high performance liquid chromatography electrospray tandem mass spectrometry. The most effective macroporous resin was selected by comparing the adsorption performance of five different types of macroporous resins (Diaion Hp20, Sepabeads Sp70, Sepabeads Sp207, Sepabeads Sp700, and Sepabeads Sp710). Equilibrium adsorption isotherms of five resins with wastewater were measured and analyzed using Langmuir and Freundlich isotherm models. Both Langmuir and Freundlich models could describe the adsorption process. The adsorption and desorption behaviors of anthocyanins were studied using a dynamic method on the five types of resins, and Sp700 presented the highest adsorption capacity as well as desorption capacity, indicating that Sp700 is a good candidate for purification of anthocyanins from black bean canning wastewater. The most effective adsorption conditions were tested using Sp700. Dynamic adsorption and desorption were performed in glass columns packed with Sepabead Sp700 to optimize the purification process. Temperature during adsorption and desorption (25°C and 35°C) did not significantly affect the adsorption and desorption ratio. Adsorption ratio was significantly reduced when the flow rate increased from 1.5 mL/min to 2.5 mL/min. However, desorption ratio was not affected by flow rate (from 1.5mL/min to 0.3mL/min). Ethanol concentration (from 30% to 60%) did not affect desorption ratio. Four kinds of anthocyanins were identified in black bean canning wastewater. The major anthocyanins were delphinidin 3-glucoside, petunidin 3-glucoside, and maldvidin 3-glucoside, with a small amount of petunidin 3, 5-diglucoside also in the final product