Multienzyme Cascade Synthesis of Rare Sugars From Glycerol in Bacillus subtilis

Area of Science:

• Biotechnology
• Metabolic Engineering
• Synthetic Biology

Background:

• Rare sugars are valuable monosaccharides with diverse industrial applications.
• Current production methods like enzymatic synthesis are costly and complex.
• Escherichia coli, while used for rare sugar synthesis, poses safety concerns.
• There is a need for safe and efficient microbial strains for rare sugar production.

Purpose of the Study:

• To develop a safe and efficient whole-cell bioconversion system for rare sugar production.
• To engineer Bacillus subtilis as a production chassis for rare sugars.
• To optimize the expression of key enzymes for enhanced rare sugar biosynthesis.

Main Methods:

• Heterologous expression of three key genes (aldO, rhaD, yqaB) in Bacillus subtilis.
• Investigation and optimization of different promoters to enhance enzyme expression.
• Whole-cell conversion of glycerol to rare sugars using engineered B. subtilis.
• Fed-batch cultivation for maximizing rare sugar production.

Main Results:

• Engineered B. subtilis successfully converted glycerol into D-allulose and D-sorbose.
• Optimized enzyme expression led to a maximum production titer of 16.96 g/L.
• Fed-batch fermentation achieved a record titer of 26.68 g/L rare sugars from glycerol.
• A high conversion yield of 33.9% from glycerol was obtained.

Conclusions:

• Demonstrated an efficient and cost-effective whole-cell bioconversion method for rare sugar synthesis.
• Established a food-grade production platform using Bacillus subtilis.
• The developed system has the potential to meet the growing industrial demand for rare sugars.