Opportunities toward hydrogen production biotechnologies.

Hydrogen is already a major commodity and process intermediate for fertilizer production, petroleum processing, and chemical synthesis. It also offers unrealized potential for energy storage. While biological production offers an expandable and sustainable source, enthusiasm has been dampened by slow research progress. Also, the very low cost of natural gas (the major current hydrogen source) imposes severe economic challenges. This discussion describes process, metabolic, and protein engineering opportunities toward cost-effective biohydrogen production. Recent progress in hydrogenase engineering and photosynthetic bacterial research now suggests a favorable risk versus reward opportunity. Although the risks are still significant, successful technologies would provide important components in an integrated energy portfolio that enables global sustainability.