IMPROVEMENT OF PRODUCTIVITY IN ACETIC-ACID FERMENTATION WITH CLOSTRIDIUM-THERMOACETICUM

Production of acetic acid by a mutant strain of Clostridium thermoacet icum was compared in three types of membrane cell-recycle bioreactors. A modified fed-batch bioreactor (where the product is partially remov ed at the end of fermentation, but the cells are retained), and a two- stage CSTR (with product being removed continuously and the cells bein g recycled from the second to the first stage) resulted in better perf ormance than a one-stage CSTR or batch fermenter. The difference in pe rformance was greater at higher acetate concentration. With 45 g/L of glucose in the feed, productivity was 0.75-1.12 g/L . h and acetic aci d concentrations were 34-38 g/L. This is more than double the batch sy stem. The nutrient supply rate also appeared to have a strong influenc e on productivity of the microorganism.