Deleting pck improves growth and suppresses by‐product formation during 1,3‐propanediol fermentation by Klebsiella pneumoniae

Aims To investigate the role of phosphoenolpyruvate (PEP) carboxylation in cell metabolism in Klebsiella pneumoniae. Methods and Results The effects of deleting pck, which encodes PEP carboxykinase (PCK), and/or ppc, which encodes PEP carboxylase (PPC), on growth, enzyme activity and metabolite formation of Kl. pneumoniae were investigated. A self‐regulatory mechanism of PEP carboxylation was found in ppc‐ or pck‐deficient mutants, which resulted in almost no change in succinate formation. However, almost no growth was observed in a ppc‐ and pck‐deficient mutant. Interestingly, only deleting pck affected the energy metabolism and promoted aerobic cell growth. Under micro‐aerobic conditions, although there was only a small (8·1%) increase of 1,3‐propanediol production by such pck‐deficient mutant during a 2‐l fed‐batch process, the by‐products 2,3‐butanediol and acetate significantly decreased by 73·0% and 54·8%, respectively, compared with those in the parent strain. Conclusions PEP carboxylation could be a critical anaplerotic reaction for converting C3 to C4 metabolites in the central metabolism of Kl. pneumoniae. Significance and Impact of the Study This study is the first to identify the critical role of PEP carboxylation, as well as those of PPC and PCK, which are responsible for this reaction, in Kl. pneumoniae. In addition, the pck‐deficient mutant was proven to be a valuable 1,3‐propanediol producer.