Enhancing H₂ production in Green Algae with Peptides and scFvs Discovered by Phage Display

Emission of greenhouse gases, such as CO₂ and methane, is one of the main drivers of climate change, and specifically of global warming. These gases are emitted due to fossil fuels combustion, agriculture, and other processes. Hydrogen has been proposed as a clean energy resource, since its burning emits only water and releases energy. Currently, most of the hydrogen is produced by polluting chemical reactions, which involve greenhouse gases.

During photosynthesis, electrons are transferred to the enzyme ferredoxin-NADP+ oxidoreductase (FNR) for carbon fixation. Alternatively, electrons can be transferred to the enzyme hydrogenase for hydrogen production by converting two photons and two electrons into gaseous hydrogen. Hydrogenase is present in most photosynthetic microorganisms, including our model organism – the green algae Chlamydomonas reinhardtii. For several reasons, FNR imposes great competition on hydrogenase over electrons.

Phage display is a groundbreaking technique for constructing libraries of phages which present highly diverse peptides or proteins on their coat proteins. One popular type of displayed protein is a single chain variable fragment (scFv) – a fusion protein composed of the variable domains of an antibody connected by a linker. In a process called "panning", target-binding peptides or proteins can be selected and enriched.

In my research, I screen peptides and scFvs phage display libraries for ones that associate with FNR and inhibit its ability to accept electrons, rerouting the electron flow toward hydrogenase and subsequently increasing hydrogen production.