[Efficient cascade biosynthesis of (S)-2-hydroxybutyric acid]

Area of Science:

• Biotechnology
• Metabolic Engineering
• Synthetic Biology

Background:

• 2-Hydroxybutyric acid (2-HBA) is a crucial intermediate for biodegradable materials and pharmaceuticals.
• Chemical synthesis of 2-HBA yields a racemic mixture, necessitating costly deracemization for enantiomerically pure forms.

Purpose of the Study:

• To develop an efficient microbial biosynthesis system for optically pure (S)-2-HBA.
• To engineer a coordinated multi-enzyme cascade in Escherichia coli for high-titer production from L-threonine.

Main Methods:

• Coexpression of L-threonine deaminase (TD), L-lactate dehydrogenase (LDH), and formate dehydrogenase (FDH) in E. coli BL21.
• Promoter engineering to fine-tune enzyme expression and balance metabolic flux.
• Development of a recombinant strain (P21285FDH-T7V7827) with a tunable expression system.

Main Results:

• The engineered strain P21285FDH-T7V7827 produced (S)-2-HBA with a highest titer of 143 g/L.
• Achieved a high molar yield of 97% within 16 hours.
• The titer is approximately 1.83 times higher than previously reported yields.

Conclusions:

• A coordinated multi-enzyme expression system in a single cell significantly enhances hydroxyl acid biosynthesis.
• The developed strain shows substantial promise for the industrial-scale production of (S)-2-HBA.
• This approach offers a sustainable alternative to chemical synthesis and deracemization.