Enhanced Chloroplast-Mitochondria Crosstalk Promotes Ambient Algal-H2 Production

Microalgae are natural biocatalysts of Hydrogen. Their ability to convert solar energy to valuable compounds with minimal ecological footprint potentially puts them as significant contributors to clean energy transition. Currently, this process, although promising, is not scalable because it is limited to oxygen-free conditions and is short-lived due to electron loss to other processes, mainly carbon fixation. Here we show that a strain, defected in thylakoid proton gradient regulation, ∆pgr5, bypasses both challenges simultaneously, leading to a prolonged 12-day hydrogen production under ambient mixotrophic conditions in a one-liter set-up. We report that ∆pgr5 possess a repressed ability to fixate carbon and this limitation is counterbalanced by an enhanced chloroplast-mitochondrion energetic exchange. This unique physiology supported the simplistic, yet robust and scalable hydrogen production capability of ∆pgr5.