The design of culture media based on the elemental composition of biological material

During growth, living organisms absorb chemical elements from their environment in ratios as they occur in their tissues. In lower organisms (micro organisms, plants), as well as in animal cell and tissue culture, the elements are absorbed as small molecules or as free ions, potentially affecting the relative ionic composition of their medium. To avoid these changes in the medium composition, the elements in culture media should be available in the same ratios as in which they occur in biological material. This paper shows how, by using linear programming algorithms, culture media can be designed which approximate the average elemental composition of biological material, By mixing inorganic salts a culture medium can be prepared containing most of the major elements almost exactly in the ratios in which they occur in living material. Although certain deviations have to be allowed for the three most abundant elements (O, C, H), these can be justified by assuming that these elements will normally not act as limiting factors, as in an open system they can be supplemented by water and carbon dioxide from the air. With addition of an organic compound, e.g., glucose, the average elementary composition of biological material can even be matched exactly.