The production of L-lysine by a homoserine and leucine requiring strain of Corynebacterium glutamicum ATCC 21513 was studied. O-2 limitation caused a decrease in both substrate consumption rate and the conversion efficiency of substrate to L-lysine, concomitant with formation of L-lactate and isobutyric acid. The maximum conversion rate into L-lysine was obtained at 30-35% dissolved oxygen saturation and at a redox potential up to -140 mV Increased CO2 levels increased biomass yield and considerably decreased formation of organic acids. Under optimal oxygen conditions, without CO2 addition a decrease of 33% in isobutyric acid and 26% in lactate production and an increase of 20% in L-lysine production were obtained compared with cultures grown under 15-20% of O-2 saturation.