H₂-driven xylitol production in Cupriavidus necator H16

Area of Science:

• Biotechnology
• Green Chemistry
• Metabolic Engineering

Background:

• Biocatalysis presents a sustainable alternative to traditional chemical synthesis.
• Hydrogen serves as an efficient and renewable reducing agent for cofactor regeneration in biocatalytic processes.
• Cupriavidus necator H16, engineered with NAD-dependent hydrogenase, facilitates cofactor recycling.

Purpose of the Study:

• To develop a biocatalytic system for D-xylose to xylitol conversion using hydrogen for cofactor regeneration.
• To heterologously express D-xylose reductase from Scheffersomyces stipitis in C. necator.
• To evaluate the efficiency of hydrogen-driven cofactor recycling in the engineered microbial host.

Main Methods:

• Heterologous expression of D-xylose reductase in Cupriavidus necator.
• Bioconversion of D-xylose to xylitol using resting cells and hydrogen as the reducing agent.
• Analysis of cofactor recycling efficiency and product yield.

Main Results:

• Successful expression of D-xylose reductase enabled near-complete conversion of 30 g/L D-xylose to xylitol.
• Over 90% of hydrogen-derived energy and protons were utilized for the bioconversion, indicating high system efficiency.
• The engineered C. necator chassis also produced L-arabitol and D-ribitol from their respective substrates, achieving a maximum xylitol productivity of 0.7 g/L/h.

Conclusions:

• Renewable hydrogen is an effective reducing agent for powering cofactor recycling in biocatalysis.
• Hydrogen-oxidizing bacteria like C. necator are suitable hosts for hydrogen-driven biocatalytic applications.
• This study demonstrates a promising pathway for sustainable production of sugar alcohols.