Selective flocculation and precipitation for the improvement of virus-likeparticle recovery from yeast homogenate

The purification of an intracellular product from a complex mixture of cont aminants after cell disruption is a common problem in processes downstream of fermentation systems. This is particularly challenging for the recovery of particulate (80 nm in diameter) multimeric protein products, named virus -like particles (VLPs), from cell debris and other intracellular components . Selective flocculation for debris removal followed by selective precipita tion of the target protein can be used as a preclarification step to aid pu rification. In this paper, selective borax flocculation of cell debris in y east homogenate, followed by selective poly(ethylene glycol) precipitation of VLPs are defined with a view to demonstrating their potential in aiding the initial clarification stages of the purification sequence. The translat ion from laboratory scale to pilot scale operation is addressed, demonstrat ing the challenge of scale-up of solid-liquid separation stages for biologi cal particle processing.