Abstract: Bioprocessing apparatus and method using centrifugal acceleration of cells to maintain a culture within a reaction zone. The reactor has an inflow at a relatively distance inlet and an outflow at an inwardly spaced point toward the rotational axis. The reaction chamber has an inwardly diverging zone with a velocity gradient which captures cells of varying sizes. A recycle system is preferably used to recycle medium containing nutrients for the culture microbes. Byproducts of the cells are removed by the circulated medium and can be extracted using a desired extraction process.