The upstream part of a bioprocess refers to the initial stage in which microbes/cells are grown, e.g. bacterial or mammalian cell lines in bioreactors. Upstream processing involves all the steps related with inoculum development: Media Preparation, Cell Culture and Cell Separation & Harvest. When the cells have reached the desired density, they are harvested and moved to the downstream section of the bioprocess.
Upstream processing is usually divided into the following stages: