Engineering central pathways for industrial-level (3R)-acetoin biosynthesis in Corynebacterium glutamicum

Area of Science:

• Biotechnology
• Metabolic Engineering
• Synthetic Biology

Background:

• Acetoin is a high-value bio-based chemical and pharmaceutical intermediate.
• Optically pure acetoin enantiomers are desirable but difficult to produce efficiently.
• Previous engineering of Corynebacterium glutamicum for (3R)-acetoin production yielded unsatisfactory results.

Purpose of the Study:

• To further enhance the production of optically pure (3R)-acetoin using advanced metabolic engineering strategies.
• To overcome limitations in yield and productivity for industrial-scale bioprocesses.

Main Methods:

• Redirecting cellular carbon flux towards acetoin synthesis in C. glutamicum.
• Implementing strategies such as blocking anaplerotic pathways and attenuating TCA cycle genes.
• Integrating additional copies of the alsSD operon and inactivating specific enzymes like citrate synthase and phosphoenolpyruvate carboxylase.

Main Results:

• The optimal engineered strain (CGS11) achieved a titer of 102.45 g/L (3R)-acetoin.
• A high product yield of 0.419 g/g glucose and productivity of 1.86 g/L/h were obtained.
• Optical purity of the produced (3R)-acetoin exceeded 95%.

Conclusions:

• This study presents the highest reported titer of enantiomerically enriched (3R)-acetoin.
• The developed green fermentation process is efficient, economical, and environmentally friendly.
• This work paves the way for industrial-scale, sustainable production of (3R)-acetoin.