Abstract: A yeast storage and transfer vessel having semi-permeable materials and a method for transfer of liquid yeast to a fermentor using said vessel and a peristaltic pump. In some embodiments, one or more opening(s) may include a port and valves and/or filters allowing the egress of carbon dioxide and other fermentation gases out of the yeast vessel. The bag storage vessel materials may also include semi-permeable materials. The herein disclosed apparatus and method permit the sterile transfer and mixing of yeast and/or fermentation product into a variety of fermentors, in addition to sterile pumping action in the reverse direction.