Theoretically possible yields of microbial secondary products

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Abstract
Balance equations for some representatives of the main biogenetic groups of secondary metabolites were formulated which provide the known and probable reactions within the biosynthetic routes. The calculated yields Ymaxp/s with respect to the usual substrate glucose range between 0.37 and 0.9 and, obviously, they agree well with the theoretical yields of biochemically related parts of cell dry mass. The sugar derivatives correspond to carbohydrates, the β‐lactams and shikimate derivatives to proteins, and finally, the polyketides and mevalonate derivatives to lipids. From this stoichiometric point of view the secondary metabolism thus seems to possess the same biosynthetic efficiency as adequate parts of primary metabolism under the conditions of retarded growth. The introduction of the Ymaxp/s values into an equation for substrate consumption regarding the growth, maintenance and product formation (van der Beek and Roels 1984) delivered yields which demonstrated that more than 70% of the glucose flowed into byproducts or waste metabolites, respectively.