Abstract: Provided herein are methods and systems for production (e.g., batch production) of a polypeptide product via cell culture. In some embodiments, the methods and systems use a first bioreactor (e.g., for cell culturing), an alternating tangential flow (ATF) microfilter (e.g., for removing a polypeptide product and culture medium from the cell culture while retaining cells), a second bioreactor (e.g., for concentrating the product), and an ATF ultrafilter (e.g., for retaining product in the second bioreactor and allowing culture medium to exit).