Since in all but very special circumstances microbial
cultures do not do any useful work, Wç can usually
be disregarded. At this point, the equation may
be simpli¢ed further by introducing the important
concept that the entropy of a living cell should not
increase. This may be done by assuming that the
cellular composition remains constant and thus by
considering the live cell as a catalytic unit operating
at a steady state. The new cells (biomass) formed by
growth would then be regarded as yet another metabolic
product.