Method for producing product

A method for producing a product that is produced by cells accommodated in a culture vessel, the method comprising:

• performing a separation treatment of separating a cell suspension extracted from the culture vessel using a pump, into a cell concentrate having cells concentrated therein and a liquid having a cell concentration that is lower than that of the cell suspension;
• returning the cell concentrate to the culture vessel;
• and
• supplying a fresh medium into the culture vessel,
• wherein the cell concentration in the culture vessel is maintained at a value of from 3×107 cells/ml to 3×108 cell/ml,
• the pump is a magnetic levitation type pump in which a rotating blade suspended in the cell suspension is rotated by a magnetic force, and
• in a case in which a diameter of the rotating blade is designated as D meters:
• a distance between a tip of the rotating blade and an inner wall surrounding a periphery of the rotating blade is designated as L meters;
• a rotation speed per second of the rotating blade is designated as R:
• a ratio of a circumference to a diameter of a circle is designated as π;
• a viscosity of the cell suspension is designated as X pascal-seconds;
• a liquid feeding pressure of the pump is designated as P pascals;
• and a shear stress acting on the cell suspension by rotation of the rotating blade is designated as Y, which is calculated by Y=X×D×π×R/L,
• the pump is operated such that following relationships are satisfied:
• 2,000≤10,000Y+P≤80,000 and
• 3≤log10(P/Y)≤5.6,
• so that the cells are selectively reduced by applying an external force caused by the liquid flow generated by the pump to the cells, to thereby obtain a distribution of cells in the culture vessel such that:
• in a case in which an average diameter of single cells in the culture vessel is designated as A, the number proportion of cells having a single cell diameter of 1.4×A or greater is 5% or less;
• and
• the number proportion of cells having a single cell diameter in the range of A±A/7 is 50% or more.