In an article in the preceding issue we discussed the design and construction of fermenters in which antibiotics are cultured. For industrial purposes these fermenters can range in size up to 500 m[cube]. They have to be sterilized, filled with sterile culture medium and the culture itself and supplied with oxygen continuously. In some cases they must be given additional feeds during the fermentation run. This article looks at some of the problems of supplying the culture medium and maintaining it at the optimum operating conditions.