Microbial production of hydrogen: an overview

Area of Science:

• Microbiology
• Biotechnology
• Sustainable Energy

Background:

• Hydrogen (H2) is a clean energy carrier with significant potential.
• Diverse microbial groups, including anaerobes, aerobes, methylotrophs, and photosynthetic bacteria, can produce H2.
• Optimizing microbial H2 production is crucial for developing sustainable bioenergy solutions.

Purpose of the Study:

• To review and assess the potential of various microorganisms for hydrogen production.
• To evaluate the efficiency and productivity of different bacterial strains and co-cultures.
• To explore the feasibility of using immobilized microbial systems for continuous H2 generation.

Main Methods:

• Screening of anaerobic, facultative anaerobic, aerobic, methylotrophic, and photosynthetic bacteria for H2 production.
• Utilizing immobilized microbial cells (e.g., Clostridia, Escherichia coli, Bacillus licheniformis, Anabaena cylindrica) to enhance H2 yield and stability.
• Investigating co-cultures and hydrogenase uptake (Hup) mutants to improve H2 productivity.
• Assessing H2 production from various substrates like glucose, monosaccharides, acetate, succinate, malate, and cellulose.
• Exploring simultaneous production of oxychemicals and H2.

Main Results:

• Immobilized Clostridium butyricum achieved 50% efficiency (2 mol H2/mol glucose).
• Immobilized Escherichia coli demonstrated 100% efficiency from formate and 60% from glucose.
• Ruminococcus albus showed promise among methylotrophs (2.37 mol H2/mol glucose).
• Photosynthetic Rhodospirillum rubrum produced 4-7 mol H2 from different organic acids.
• Co-cultures of Cellulomonas and a R. capsulata Hup mutant yielded 6.2 mol H2/mol glucose from cellulose.
• Immobilized Anabaena cylindrica produced H2 continuously for one year.
• Hup mutants of Anabaena variabilis showed increased H2 productivity.

Conclusions:

• A wide range of microorganisms can be harnessed for hydrogen production, offering diverse substrate utilization and production efficiencies.
• Immobilization techniques and genetic modifications (Hup mutants) significantly enhance hydrogen yield and process stability.
• Microbial hydrogen production holds considerable promise for sustainable energy, with its future intertwined with fossil fuel availability and environmental concerns.