Movement of a slot door of a freeze dryer is driven by a rack and pinion actuator. The actuator is easily sanitized and includes internal elements that are accessible to sanitizing sprays. The pinions are driven by pinion shafts that pass through a seal separating an aseptic area from a non-aseptic area where the drive train is positioned. Only rotary motion is transferred across the aseptic barrier, reducing the need for a bellows or sliding covers, which are difficult to sanitize.