Purification of wheat germ agglutinin using affinity flocculation with chitosan and a subsequent centrifugation or flotation step.

Affinity purification is by tradition almost equivalent to affinity chromatography. In this report, a purification process is described in which the affinity interaction is performed in free solution. A precipitation step follows, thereby separating the affinity bound material from free. Chitosan is used as a natural polyligand rich in N-acetyl-D-glucosamine and is, because of its specificity, used in affinity precipitation of wheat germ agglutinin (WGA). The polyligand is soluble at pH below 6.5 and precipitates at higher values, thus coprecipitating associated WGA. A process was developed where the overall yield of WGA was 70% and the final product gave a single band on SDS-PAGE. The process was also run on a larger scale, where even affinity flotation was included in the study as an alternative way to harvest the precipitate. Scaling up the affinity precipitation was a very easy task.