On the entropy balance of microbial product formation

Abstract

An approach of Bermudez & Wagensberg (1986; J. theor. Biol. 122, 347), concerning the entropy balance of growing microorganisms, was modified by consideration of non-growth-coupled product formation as well as maintenance metabolism besides the growth-related metabolism. The obtained equation of entropy variation as the sum of entropy production and entropy transfer includes four resistance coefficients, Rmn, instead of the coupling coefficient L, given by Bermudez & Wagensberg. The determination of the R's can be achieved, supposing steady-states of heat evolution, if different conditions are ascertained within a microbial metabolite producing process, e.g. submerged fermentation process, steady-state of growth rate by absence of product formation (i), steady-state of product formation by absence of growth (ii), steady-states of growth rate and product formation rate (iii), and constancy of maintenance coefficient (iv). The introduction of the actual date of experiments into the equations allows the determination of the time course of entropy balance during the particular phases of the fermentation process.