Erratum to: Production of isobutanol from crude glycerol by a genetically-engineered Klebsiella pneumoniae strain

The pyruvate decarboxylase activity of IpdC is a limitation for isobutanol production by Klebsiella pneumoniae

Background

Klebsiella pneumoniae contains an endogenous isobutanol synthesis pathway. The ipdC gene annotated as an indole-3-pyruvate decarboxylase (Kp-IpdC), was identified to catalyze the formation of isobutyraldehyde from 2-ketoisovalerate.

Results

Compared with 2-ketoisovalerate decarboxylase from Lactococcus lactis (KivD), a decarboxylase commonly used in artificial isobutanol synthesis pathways, Kp-IpdC has an 2.8-fold lower K_m for 2-ketoisovalerate, leading to higher isobutanol production without induction. However, expression of ipdC by IPTG induction resulted in a low isobutanol titer. In vitro enzymatic reactions showed that Kp-IpdC exhibits promiscuous pyruvate decarboxylase activity, which adversely consume the available pyruvate precursor for isobutanol synthesis. To address this, we have engineered Kp-IpdC to reduce pyruvate decarboxylase activity. From computational modeling, we identified 10 amino acid residues surrounding the active site for mutagenesis. Ten designs consisting of eight single-point mutants and two double-point mutants were selected for exploration. Mutants L546W and T290L that showed only 5.1% and 22.1% of catalytic efficiency on pyruvate compared to Kp-IpdC, were then expressed in K. pneumoniae for in vivo testing. Isobutanol production by K. pneumoniae T290L was 25% higher than that of the control strain, and a final titer of 5.5 g/L isobutanol was obtained with a substrate conversion ratio of 0.16 mol/mol glucose.

Conclusions

This research provides a new way to improve the efficiency of the biological route of isobutanol production.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13068-022-02144-8.

Kp-IpdC is more efficient than KivD for 2-ketoisovalerate decarboxylation.

Pyruvate decarboxylase activity is a limitation of Kp-IpdC.

T290L variant exhibits a decreased pyruvate decarboxylase activity.

Isobutanol production by K. pneumoniae T290L was improved.

Identification and characterization of a short-chain acyl dehydrogenase from Klebsiella pneumoniae and its application for high-level production of L-2,3-butanediol

Klebsiella pneumoniae synthesize large amounts of L-2,3-butanediol (L-2,3-BD), but the underlying mechanism has been unknown. In this study, we provide the first identification and characterization of an L-2,3-BD dehydrogenase from K. pneumoniae, demonstrating its reductive activities toward diacetyl and acetoin, and oxidative activity toward L-2,3-BD. Optimum pH, temperature, and kinetics determined for reductive and oxidative reactions support the preferential production of 2,3-BD during cell growth. Synthesis of L-2,3-BD was remarkably enhanced by increasing gene dosage, reaching levels that, to the best of our knowledge, are the highest achieved to date.