Upstream (bioprocess) - Downstream

Downstream

The downstream part of a bioprocess refers to the part where the cell mass from the upstream are processed to meet purity and quality requirements. Downstream processing is usually divided into three main sections: Cell disruption, a purification section and a polishing section. The volatile products can be separated by distillation of the harvested culture without pre-treatment. Distillation is done at reduced pressure at continuous stills. At reduced pressure distillation of product directly from fermentor may be possible. The steps of downstream processing are:

1. separation of biomass: separating the biomass (microbial cells) generally carried out by centrifugation or ultra-centrifugation. If the product is biomass, then it is recovered for processing and spent medium is discarded. If the product is extra cellular the biomass will be discarded.Ultra filtration is an alternative to the centrifugation.
2. cell disruption: If the desired product is intra cellular the cell biomass can be disrupted so that the product should be released. The solid-liquid is separated by centrifugation or filtration and cell debris are discarded.
3. concentration of broth: The spent medium is concentrated if the product is extracellular.
4. initial purification of metabolites: According to the physico-chemical nature of the product molecule several methods for recovery of product from the clarified fermented broth were used ( precipitation,
5. de-watering: If low amount of product is found in very large volume of spent medium, the volume is reduced by removing water to concentrate the product. It is done by vacuum drying or reverse osmosis.
6. polishing of metabolites: this is the final step of making the product to 98 to 100% pure.the purified product is mixed with several inert ingredients called excipients. the formulated product is packed and sent to the market for the consumers.