Microbial Conversion of Glycerol to 1,3-Propanediol by an Engineered Strain of Escherichia coli

Abstract

In an effort to improve industrial production of 1,3-propanediol (1,3-PD), we engineered a novel polycistronic operon under the control of the temperature-sensitive lambda phage P L P R promoter regulated by the cIts857 repressor and expressed it in Escherichia coli K-12 ER2925. The genes for the production of 1,3-PD in Clostridium butyricum, dhaB1 and dhaB2, which encode the vitamin B 12 -independent glycerol dehydratase DhaB1 and its activating factor, DhaB2, respectively, were tandemly arrayed with the E. coli yqhD gene, which encodes the 1,3-propanediol oxidoreductase isoenzyme YqhD, an NADP-dependent dehydrogenase that can directly convert glycerol to 1,3-PD. The microbial conversion of 1,3-PD from glycerol by this recombinant E. coli strain was studied in a two-stage fermentation process. During the first stage, a novel high-cell-density fermentation step, there was significant cell growth and the majority of the metabolites produced were organic acids, mainly acetate. During the second stage, glycerol from the fresh medium was rapidly converted to 1,3-PD following a temperature shift from 30°C to 42°C. The by-products were mainly pyruvate and acetate. During this two-stage process, the overall 1,3-PD yield and productivity reached 104.4 g/liter and 2.61 g/liter/h, respectively, and the conversion rate of glycerol to 1,3-PD reached 90.2% (g/g). To our knowledge, this is the highest reported yield and productivity efficiency of 1,3-PD with glycerol as the sole source of carbon. Furthermore, the overall fermentation time was only 40 h, shorter than that of any other reports.

YqhD: a broad-substrate range aldehyde reductase with various applications in production of biorenewable fuels and chemicals

“…Others have used YqhD in combination with the Clostridium butyricum DHA pathway in E. coli: co-expression of yqhD with dhaB1 and dhaB2 resulted in a strain that produced 104.4 g/L 1,3-PD from glycerol with a productivity of 2.61 g/L/hr (Tang et al 2009). …”

Anaerobic and micro-aerobic 1,3-propanediol production by engineered Escherichia coli with dha genes from Klebsiella pneumoniae GLC29

“…In an effort to maximize 1,3-PDO yield and concomitantly minimize production time and byproduct, Tang et al (2009) established a two-stage two-substrate fermentation for producing 1,3-PDO by an engineered E. coli K-12 ER2925 strain, and dhaB1 and dhaB2 from C. butyricum SYU 20108 were cloned and expressed in the host strain. On the first stage from 0 to 10 h, dissolved oxygen was maintained above 40% air saturation, glucose was added continuously to maintain up to 25 g/L until a final biomass of 26 g/L DCW was reached.…”

Biorefinery for Glycerol Rich Biodiesel Industry Waste

“…Here, the maximum 1,3-PD concentrations achieved were 43.2 and 54.2 g/L, respectively [25]. Genetically modified Escherichia coli strain carrying dhaB1 and dhaB2 (encoding for vitamin B12 independent glycerol dehydratase and its activator, respectively) from C. butyricum along with E. coli yqhD gene (encoding for 1,3-PDO oxidoreductase isoenzyme, YqhD) gave a 1,3-PDO yield of 104.4 g/L and a productivity of 2.61 g/L/h from glycerol as C source [26].…”