Systems and methods for cell culturing

A method for culturing cells, the method comprising:

• culturing cells in a cell culture chamber on a cell culture instrument by flowing a cell culture medium through the cell culture chamber, thereby effectuating gas exchange between one or more cells in the cell culture chamber and the cell culture medium and producing used cell culture medium;
• removing used cell culture medium from the cell culture chamber and measuring one or more parameters thereof;
• assessing whether the one or more parameters of the used cell culture medium meet a predetermined threshold;
• and
• recycling and/or discarding one or more portions of the used cell culture medium based, at least in part, on the assessing step by directing, via a valve, flow of one or more portions of used cell culture medium back into the cell culture chamber or to a waste reservoir, respectively,
• wherein the recycling step comprises flowing a portion of the used cell culture medium, that has already been flowed through the cell culture chamber and meets the predetermined threshold of the measured parameters, back into the cell culture chamber during the cell culturing process and wherein a rate of recycle is based, at least in part, on required gas exchange and nutrient supply for the cell culturing, and
• wherein the discarding step comprises flowing a portion of the used cell culture medium, that has already been flowed through the cell culture chamber and does not meet the predetermined threshold of measured parameters, to the waste reservoir.