Light-induced H₂ generation in a photosystem I-O₂-tolerant [FeFe] hydrogenase nanoconstruct

Area of Science:

• Bioengineering
• Renewable Energy
• Photosynthesis

Background:

• Fusion of hydrogenases and photosynthetic reaction centers (RCs) is a key strategy for sustainable biofuel production.
• Type I RCs can transfer electrons to hydrogenases for proton reduction to dihydrogen (H2).
• Existing hydrogenase systems face limitations like oxygen (O2) sensitivity and low production rates.

Purpose of the Study:

• To develop an oxygen-tolerant hydrogenase-Photosystem I (PS I) nanoconstruct for enhanced hydrogen production.
• To investigate the efficacy of fusing PsaE, a PS I subunit, to an oxygen-tolerant [FeFe] hydrogenase.

Main Methods:

• Fusion of PsaE from Photosystem I (PS I) to an O2-tolerant [FeFe] hydrogenase (CbHydA1) using a flexible [GGS]4 linker.
• In vitro synthetic activation of the CbHydA1-PsaE chimera.
• Quantitative binding of the chimera to a PS I variant lacking PsaE.

Main Results:

• The CbHydA1-PsaE chimera demonstrated bidirectional activity upon synthetic activation.
• The nanoconstruct generated H2 at 84.9 ± 3.1 µmol H2 mgchl−1 h−1 under anaerobic conditions.
• The nanoconstruct retained H2 generation ability in the presence of O2, albeit at a reduced rate (2.2 ± 0.5 µmol H2 mgchl−1 h−1).

Conclusions:

• PsaE serves as a viable scaffold for developing PS I-based nanoconstructs.
• The use of an O2-tolerant [FeFe] hydrogenase enables H2 generation in the presence of oxygen.
• This research opens possibilities for in vivo H2 generating systems that are oxygen-tolerant.