Downstream processing refers to the sequence of operations required to recover and purify a biological product, such as a therapeutic protein or vaccine, following its synthesis in an upstream process like fermentation or cell culture. The primary objective is to isolate the target molecule from the complex mixture of cell debris, culture media, and other contaminants it was produced in. This multi-step process typically involves initial recovery and clarification (e.g., centrifugation, filtration), followed by purification and concentration using techniques like chromatography, and concluding with formulation to ensure the final product has the required purity, stability, and activity for its intended application. As a critical component of bioprocess engineering, downstream processing focuses on designing scalable, efficient, and cost-effective purification schemes that meet stringent quality and safety standards.