Physiologic mechanisms of sequential products synthesis in 1,3‐propanediol fed‐batch fermentation by Klebsiella pneumoniae

Abstract

The glycerol fed-batch fermentation by Klebsiella pneumoniae CGMCC 1.6366 exhibited the sequential synthesis of products, including acetate, 1,3-propanediol (1,3-PD), 2,3-butanediol, ethanol, succinate, and lactate. The dominant flux distribution was shifted from acetate formation to 1,3-PD formation in early- exponential growth phase and then to lactate synthesis in late-exponential growth phase. The underlying physiological mechanism of the above observations has been investigated via the related enzymes, nucleotide, and intermediary metabolites analysis. The carbon flow shift is dictated by the intrinsic physiological state and enzymatic activity regulation. Especially, the internal redox state could serve as a rate-controlling factor for 1,3-PD production. The q(1,3-PD) formation was the combined outcomes of regulations of glycerol dehydratase activity and internal redox balancing. The q(ethanol)/q(acetate) ratios demonstrated the flexible adaptation mechanism of K. pneumoniae preferring ATP generation in early-exponential growth phase. A low PEP to pyruvate ratio corresponded LDH activity increase, leading to lactate accumulation in stationary phase.

Dynamics of Cathode-Associated Microbial Communities and Metabolite Profiles in a Glycerol-Fed Bioelectrochemical System

“…In contrast, little is known about the organisms that proliferate in cathodic environments. Current supply is believed to favor reductive processes by enhancing the ability of cells to regenerate NADH (2,13,14). Possible mechanisms include (i) the shuttling of electrons to microorganisms via hydrogen produced at the cathode, (ii) electron shuttling to organisms via another soluble mediator, and/or (iii) direct electron transfer (DET) from the cathode to microorganisms via membrane-bound redox active components (2,8,11).…”

Ammonium and phosphate limitation in 1,3-propanediol production by Klebsiella pneumoniae

“…1,3-PD synthesis plays a key role in the consumption of NADH generated in the oxidation pathway to regulate the intracellular reducing equivalent balance of K. pneumoniae (Zeng et al 1993). The metabolic flux is shifted to 1,3-PD formation under the more reduced status to maintain the internal redox state (Zheng et al 2008b). Taken together, these findings suggest that the amount of synthesized 1,3-PD is variable, and is dependent on the nature of the limitation.…”

“…Activities of glycerol dehydratase (GDHt), 1,3-propanediol oxidoreductase (PDOR), and glycerol dehydrogenase (GDH), were measured as previously described (Zheng et al 2008b). One unit of enzyme is defined as the amount of enzyme required to produce 1 lmol product per min.…”

Integrated production for biodiesel and 1,3-propanediol with lipase-catalyzed transesterification and fermentation

“…Microbial fermentation for 1,3-PDO production from glycerol has already been extensively studied in species belonging to the family Klebsiella, Citrobacter, Clostridium, Enterobacter, and Lactobacillus (Zheng et al 2008a). Klebsiella pneumoniae is the most wildly studied strain owing to its great performance as a 1,3-PDO producer.…”