Abstract
Effect of oxygen tension on L-lysine, L-threonine and L-isoleucine accumulation was investigated. Sufficient supply of oxygen to satisfy the cell's oxygen demand was essential for the maximum production in each fermentation. The dissolved oxygen level must be controlled at greater than 0.01 atm in every fermentation, and the optimum redox potentials of culture media were above -170 rnV in L-lysine and L-threonine and above -180 mV in L-isoleucine fermentations. The maximum concentrations of the products were 45.5mg/ml for L-lysine, 10.3mg/ml for L-threonine and 15.1mg/ml for L-isoleucine. The degree of the inhibition due to oxygen limitation was slight in the fermentative production of L-lysine, L-threonine and L-isoleucine, whose biosynthesis is initiated with L-aspartic acid, in contrast to the accumulation of L-proline, L-glutamine and L-arginine, which is biosynthesized by way of L-glutamic acid.
