Yield and maintenance analysis in the chemostat; A tool for metabolic studies of growing cells

Abstract

Analogues of maintenance and yield parameters are defined with respect to gaseous and non-gaseous metabolites that are consumed or produced by energy (and carbon)-limited cell populations growing in the chemostat. The “maximum yield factors” of such metabolites (Ymaxgasand Ymaxmetfor gaseous and non-gaseous metabolites respectively) are analogues of Ymax'enthe “maximum yield factor” with respect to the energy source, while agas and amet, the “maintenance rate analogues” are comparable with aen, the “true specific maintenance rate”. Equations are derived with the help of which these parameters may be estimated. It is shown that $$\frac{{Y_{\max }^{en} }}{{Y_{\max }^{met (gas)} }} = n and \frac{{n a^{en} }}{{a^{met (gas)} }} = r$$ ; n is the mass of a gaseous or non-gaseous metabolite consumed or produced per unit mass of energy (and carbon) source consumed for growth while r is the respective mass coefficient for maintenance. These mass coefficients may be transformed into molar coefficients and separate stoichiometric equations for growth and maintenance may be written. The method is illustrated by applying it to experimental data from Herbert (1958).