Deletion of poxB, pta, and ackA improves 1,3-propanediol production by Klebsiella pneumoniae

Abstract

To date, few studies have focused on reducing the toxic by-product acetate during 1,3-propanediol production by Klebsiella pneumoniae. In this study, the effects of deleting the poxB, pta, and ackA genes, which are involved in the two main acetate synthesis pathways, on cell growth and 1,3-propanediol production were investigated. Although acetate synthesis via pyruvate oxidase (PoxB, encoded by poxB) generally seems unnecessary and wasteful, PoxB was shown to play an important role in K. pneumoniae. Deletion of poxB severely inhibited cell growth, and the poxB mutant exhibited an anomalously high accumulation of acetate in aerobic cultures and failed to produce an endogenous supply of carbon dioxide (CO2) in anaerobic cultures. It is interesting that both the aerobic and anaerobic growth defects of the poxB mutant were corrected by further deleting pta and ackA, which blocked the other main acetate synthesis pathway. The poxB-pta-ackA mutant excreted less acetate and showed an excellent ability to produce 1,3-propandiol. The final 1,3-propanediol yield and concentration in a 2-L fed-batch fermentation reached 0.66 (mol/mol) and 76.8 g/L, respectively, which were 16 and 15 % greater, respectively, than those of the parent strain.

Genetically Engineered Strains: Application and Advances for 1,3-Propanediol Production from Glycerol

“…Constructing 1,3-PD engineering strains is a promising technology. A comparison between wild strains and various genetic engineering mutants in 1,3-PD production in recent years is shown in Table 1 (20,23,(35)(36)(37)(38)(39)(40)(41)(42). The bottlenecks of glycerol bioconversion…”

“…During cell growth, lactate is accumulated in the late exponential phase, which prevents cellular growth. Therefore, many researchers have obtained lactate-deficient mutants so far to prevent the synthesis of lactate, which is of great significance for 1,3-PD fermentation (36)(37)(38). The concrete practice is knocking out the ldhA gene encoding lactate dehydrogenase.…”

“…In addition, 2,3-BD is another main byproduct of the reduction of pyruvate in glycerol-based fermentation. As 2,3-BD is also a diol like 1,3-PD, they have similar boiling points and 1,3-PD is very hydrophilic (37). Therefore, this causes a serious obstacle to efficiently separate highly pure 1,3-PD from 2,3-BD.…”

“…Therefore, elimination of acetate synthesis is the most significant target in metabolic engineering of 1,3--PD production. Lin et al (37) studied the effects of deletion of the genes poxB encoding pyruvate oxidase, pta encoding phosphotransacetylase and ackA encoding acetate kinase on cell growth and 1,3-PD yield of K. pneumoniae. These genes are all involved in the two main acetate synthesis pathways.…”

Deletingpckimproves growth and suppresses by-product formation during 1,3-propanediol fermentation byKlebsiella pneumoniae

“…to increase 1,3‐PD production (Lin et al . ). In this study, in addition to high 1,3‐PD production, a high (6·58 g l −1 ) accumulation of succinate at the end of the fermentation process was found.…”