Study On The Separation Of Lactoferrin From Whey By Expanded Bed Adsorption With Mixed-mode Adsorbent

Expanded bed adsorption is a novel bioseparation technology, which integrates the solid-liquid separation, concentration and primary purification into a unit operation. It enables direct capture of target proteins from solid particles contained feedstock. This novel unit separation operation improves separation efficiency and reduces separation cost, which makes it fit for large-scale purification process. Adsorbent specially designed is a key of the successful application of expanded bed adsorption. The mixed-mode expanded bed adsorbent, which contains both static interaction ligand and hydrophobic interaction ligand, shows high adsorption capacity, salt tolerance and other particular properties. The study selected the novel mixed-mode expanded bed adsorbent Streamline Direct CST-1 developed by GE Healthcare, separated lactoferrin and other whey proteins directly from bovinewhey.At first, the expansion characteristic and liquid mixing performances in expanded bed were studied for the novel adsorbent. The appropriate fluid velocity was determined as the expansion factor of 2, which could meet the demands of high productivity and bed stability.The second, the effects of pH and ionic strength on the adsorption of lactoferrin were investigated with the static adsorption experiments. The results indicated that CST-1 has a high adsorption capacity of lactoferrin (more than 110mg/g adsorbent), and the adsorption showed some salt-independent properties. For the elution of proteins, the adjustment of pH was more effective than that of ionic strength. The effect of pH on the adsorption of whey proteins was also investigated with the static adsorption experiments. The result indicated that CST-1 has a lower adsorption capacity of whey proteins compared with that of lactoferrin (60mg/g adsorbent), which means that a comparatively consume of whey would be needed for the efficient usage of Streamline Direct CST-1.The third, the breakthrough curve of whey proteins was investigated to determine appropriate load volume. And the effects of pH and ionic strength on the elution process were investigated. The relative content of each protein in elution wasmeasured by gel electrophoresis image analysis system. The elution process was optimized. Then the Streamline Direct CST-1 was used to direct separation of whey proteins by expanded bed adsorption with pH-step elution mode. Different whey proteins could be separated at varying pH elution, and lactoferrin was collected in the elution of 20mM NaOH. The recovery of lactoferrin was 87.8%, and the purification factor reached 10.5. The separation process demonstrated the integration advantage of expanded bed adsorption and the excellent properties of the novel mixed-mode expanded bed adsorbent.