Methods available for the preparation of microbial cells in kilogram quantities are reviewed. In general it is most convenient to grow the cells in suspension in a stirred culture vessel under controlled conditions designed to maximise the yield of the desired chemical product, and to separate them as a paste by centrifuging the mature culture. Methods for the extraction of products from such cells are discussed.
The further purification of chemical products so extracted, especially enzymes, is reviewed, with emphasis on the earlier stages in which the main aim is to obtain a quick reduction in bulk so that the final purification may be achieved on a small laboratory scale.
Examples are given, mainly from recent experience at Porton.