Comparison between Acetic Acid and Glucose as a Substrate in Threonine Fermentation

Abstract

Acetic acid and glucose were compared in their characteristics as a substrate for L-threo-nine fermentation. Maximum accumulation of threonine was 39.5mg/ml at the yield of 15.3 when acetic acid was employed as a substrate, as compared to 10.3mg/ml (10.0%) in glucose supplied culture. In acetate fed culture, maximum production could be obtained under oxygen limited condition at the value of ^rab/KrM (rate of cell respiration/maximum rate of cell respiration) 0.35_??_0.45. At the ^rab/KrM greater than 0.5, the rate of acetate assimilation increased and homoserine accumulated as a by-product resulting in poor productivity. In glucose supplied culture, however, maximum production occurred under sufficient oxygen supply at the ^rab/KrM 1.0. And oxygen limitation led to lactic acid excretion at the expense of the product. Glucose assimilation was enhanced under oxygen limited condition showing Pasteur effect in marked contrast to complete dependence of acetate assimilation upon oxygen.