PERFORMANCE OF A MULTISTAGE FERMENTER WITH CELL RECYCLE FOR CONTINUOUS ETHANOL-PRODUCTION

The unsteady and steady-state performance of a multistage fermenter wi th cell recycle is investigated numerically for continuous production of ethanol. The tanks-in-series model is employed to describe the how behaviour of culture in multiple tanks. In establishing mass balances, the cell volume fraction and the equilibrium partition coefficient fo r intracellular and extracellular ethanol concentrations are taken int o account. Kinetic expressions are taken from the literature. Compared to a single tank fermenter with recycle, multi-staging and cell recyc le are shown to bring high cell and product concentrations and low sub strate concentration in the final tank during unsteady-state operation . Solutions to the steady state model are presented graphically, showi ng concentrations as a function of dilution rate for different numbers of tanks. Results are given for the maximum ethanol productivity as a function of the optimal dilution rate, with parameters of tank number , bleed ratio and recycle ratio. Also, the effects of the fractional t ank volume and the saturation constant on the productivity and the sub strate conversion are examined.