Decrease of 3-hydroxypropionaldehyde accumulation in 1,3-propanediol production by over-expressing dhaT gene in...

Area of Science:

• Biotechnology
• Metabolic Engineering
• Industrial Microbiology

Background:

• 1,3-propanediol is a crucial monomer for producing polyesters like polytrimethylene terephthalate.
• 3-hydroxypropionaldehyde (3-HPA) is an inhibitory intermediate in glycerol fermentation to 1,3-propanediol, often causing process failure.
• Reducing 3-HPA accumulation is essential for efficient and continuous 1,3-propanediol bioproduction.

Purpose of the Study:

• To engineer Klebsiella pneumoniae to reduce the accumulation of toxic 3-HPA during 1,3-propanediol fermentation.
• To enhance the bioconversion of glycerol to 1,3-propanediol by mitigating intermediate toxicity.

Main Methods:

• Cloned and overexpressed the dhaT gene, encoding 1,3-propanediol oxidoreductase (PDOR), in Klebsiella pneumoniae TUAC01.
• Constructed a recombinant plasmid (pDK-dhaT) and transformed it into the host strain.
• Conducted scale-up fermentation experiments (5 L) using engineered and control strains with varying glycerol concentrations.

Main Results:

• Overexpression of PDOR significantly reduced peak 3-HPA levels in the fermentation broth compared to the control strain.
• At 30 g/L glycerol, 3-HPA peaked at 1.49 mmol/L in the engineered strain versus 7.55 mmol/L in the control.
• At 50 g/L glycerol, 3-HPA peaked at 2.02 mmol/L in the engineered strain versus 12.57 mmol/L in the control.

Conclusions:

• Overexpression of the dhaT gene effectively alleviates 3-HPA toxicity in Klebsiella pneumoniae.
• This metabolic engineering strategy enhances the robustness of the fermentation process for 1,3-propanediol production.
• The engineered strain shows improved performance in mitigating toxic intermediate accumulation, paving the way for more efficient bioprocesses.