Nature and significance of oscillatory behavior during solvent production by Clostridium acetobutylicum in continuous culture

The concurrent production of acids and solvents and the production of acetone during continuous culture in a product-limited chemostat indicated that the culture contained a mixture of acid- and solvent-producing cells. Periodic oscillations in the yield of end products and the specific growth rate of the culture were ob served during undisturbed continuous culture at a constant dilution rate. The increased specific growth rate was associated with an increased acid yield and an increase in the rate of cell division and the proportion of short rods. The decreased specific growth rate was as sociated with an increase in the solvent yield and a decrease in the rate of cell division, resulting in the production of elongated rods. It is proposed that the oscillatory behavior observed during continuous culture is an inherent characteristic related to the shift from primary to secondary metabolism. A major consequence of the oscillation of the specific rates of growth and division in cultures containing acid- and solvent-producing cells is that it precludes the attainment of a true steady state during continuous culture.