Effects of Photosynthesis Inhibitors on H₂ Production in Microalgae and Cyanobacteria

Area of Science:

• Biotechnology
• Renewable Energy
• Microbiology

Background:

• Photobiological hydrogen (H2) production using microalgae and cyanobacteria offers a sustainable alternative to fossil fuels.
• H2 production is limited by oxygen (O2) sensitivity of hydrogenase enzymes and O2 generated during photosynthesis.

Purpose of the Study:

• This review examines how photosynthesis inhibitors affect H2 production in microalgae and cyanobacteria.
• Focuses on molecular targets and physiological impacts of these inhibitors on H2 metabolism.

Main Methods:

• Review of studies on photosynthesis inhibitors (DCMU, atrazine, DBMIB, CCCP, KCN).
• Analysis of effects on electron transport, O2 evolution, proton gradients, and redox balance.
• Evaluation of impact on H2-evolving enzyme activity.

Main Results:

• Inhibitors alter electron transport, O2 release, proton gradients, and cellular redox balance.
• Complete inhibition of photosynthetic electron flow generally reduces sustained H2 production.
• Inhibitor effects are context-dependent, influenced by O2 suppression and respiratory O2 consumption.

Conclusions:

• Photosynthesis inhibitors are valuable mechanistic probes but not ideal for direct H2 production enhancement.
• Physiological or cultivation strategies are more reliable for establishing anaerobiosis for H2 production.
• Optimized conditions are crucial when using inhibitors as auxiliary modulators.