Cell physiology and metabolic flux distribution of Klebsiella pneumoniae under anaerobic, micro-aerobic and sufficient aerobic conditions were compared. Comparing with the anaerobic condition, the carbon flux flowed from glycerol to biomass increased 10.1% and 389.9%, while the flux flowed to 1,3-propanediol decreased 10.3% and 92.9% under micro-aerobic and sufficient aerobic conditions, respectively. Furthermore, the carbon flux flowed to TCA cycle increased 5.9% and 31.0% under such two conditions. The energy analysis results revealed that the oxygen was favorable for the NADH(2) synthesis, but excessive oxygen was disadvantage for the NADH(2) utilization in 1,3-propanediol synthesis process. So, the aeration control is significant for the aerobic 1,3-propanediol fermentation. This work is considered helpful for the further understanding of the glycerol metabolism by Klebsiella pneumoniae under aerobic condition and to establish a rational aeration control strategy for 1,3-propanediol aerobic fermentation in a large-scale bioreactor. (C) 2009 Elsevier Ltd. All rights reserved.