Posttreatment is one of the essential parts of the biochemical process, which decides the product’s quality and the whole process cost. This chapter illustrates the principles of posttreatment and its typical operation units. The process integration for posttreatment including bioreaction with separation is stressed. Additionally, the example of 2,3-butanediol fermentation is taken to show the posttreatment processes. Finally, technical and economic analysis is conducted to compare the different posttreatment methods. It has been found that integration of bioreaction with separation was the preferable method for biomass posttreatment owing to its high efficiency and low cost.