Enhanced 1,3-propanediol production in Klebsiella pneumoniae by a combined strategy of strengthening the TCA cycle and weakening the glucose effect.

AIMS: This study aimed to strengthen the reducing equivalent generation in Klebsiella pneumoniae for improving 1,3-propanediol (PDO) production.

METHODS AND RESULTS: Disruption of the arcA gene activated the transcription levels of the TCA cycle genes and thus increased the NADH/NAD+ ratio by 54·2%, leading to the improved PDO titre and yield per cell from 16·1 g l-1 and 4·0 g gDCW-1 to 18·8 g l-1 and 6·4 g gDCW-1 respectively. Further ldhA gene deletion eliminated lactate accumulation and promoted the PDO titre to 19·9 g l-1 . Finally, the glucose effect was weakened by deleting the crr gene to enhance the co-utilization of glucose and glycerol, resulting in the increased PDO production to 23·8 g l-1 with the glycerol conversion rate of 59·5%. The PDO titre in bioreactor was promoted from 61·2 to 78·1 g l-1 .

CONCLUSIONS: Deletions of the arcA and the crr genes showed positive effects on the TCA cycle activity and the co-utilization of glucose and glycerol, leading to the strengthened reducing equivalent generation and the improved PDO titre by 47·8% in shaker. The PDO titre in the bioreactor was enhanced to 78·1 g l-1 .

SIGNIFICANCE AND IMPACT OF THE STUDY: This study provided novel information on generating reducing equivalent for the PDO biosynthesis by strengthening the TCA cycle and weakening the glucose effect in K. pneumoniae.