EFFECT OF OXYGENATION AND SULFATE CONCENTRATIONS ON PYRUVATE AND LACTATE FORMATION IN KLEBSIELLA-OXYTOCA ZS GROWING IN CHEMOSTAT CULTURES

Klebsiella oxytoca ZS fermented glucose to ethanol and lactic, formic, and acetic acids, but, in contrast to many strains, accumulates pyruv ic and acetic acids as the principal end products in aerobic growth co nditions. This strain was grown in sulfate-limited chemostat at a fixe d low dilution rate (D = 0.033 h(-1)) with glucose present in excess. When oxygen was supplied at a high level, pyruvate and acetate were pr oduced, and the ratio NADH/NAD(+) was low (0.04) while the internal py ruvate concentration increased to 100 mu mol (g dry wt)(-1). A shortag e of oxygen supply was accompanied by lactate production, an increase of the ratio NADH/NAD(+) (0.53), and an undetectable level in internal pyruvate concentration. The observed changes in LDH activity found in vitro in extracts of the cells are not strictly related to those foun d in vivo. In fact, the specific activity of LDH was essentially stabl e at 30% of dissolved oxygen tension (d.o.t.) and decreased slightly a t 60% of d.o.t., whereas specific lactic acid production decreased rap idly. The in vitro LDH activity was strongly affected by the NADH/NAD( +) ratio.