A mixing device including a container defining a container cavity, the container including a bottom wall supporting a hollow shaft, the shaft supporting an impeller thereon such that the impeller is free to rotate about the shaft, the impeller including a central passageway therethrough for receiving the shaft, the container further including an elongated evacuation tube having a first end positioned within the passageway of the shaft and an opposed second end extending to a port of the container. Methods of using the mixing device to provide improved cell culture.