Abstract: A bioreactor support system configured to hold a bioreactor bag, said bioreactor support system (1) comprising: —a base module (3) comprising an impeller drive unit (5); and —at least two vessel units (11a, 11b, 11c) of different sizes, which are configured to support and substantially enclose a side wall of a bioreactor bag (111a, 111b, 111c) when a bioreactor bag is provided in the bioreactor support system (1), wherein said base module (3) and said at least two vessel units (11a, 11b, 11c) comprise mating connection devices (13a, 13b, 13c, 15a, 15b, 15c) such that the at least two vessel units (11a, 11b, 11c) can be connected to one and the same base module (3) and such that the impeller drive unit (5) of the base module (3) can be used to drive an impeller (113a, 113b, 113c) in a bioreactor bag (111a, 111b, 111c) when a bioreactor bag is provided in the bioreactor support system (1).