Photoautotrophic hydrogen production by eukaryotic microalgae under aerobic conditions

Abstract

Eukaryotic algae and cyanobacteria produce hydrogen under anaerobic and limited aerobic conditions. Here we show that novel microalgal strains (Chlorella vulgaris YSL01 and YSL16) upregulate the expression of the hydrogenase gene (HYDA) and simultaneously produce hydrogen through photosynthesis, using CO 2 as the sole source of carbon under aerobic conditions with continuous illumination. We employ dissolved oxygen regimes that represent natural aquatic conditions for microalgae. The experimental expression of HYDA and the specific activity of hydrogenase demonstrate that C. vulgaris YSL01 and YSL16 enzymatically produce hydrogen, even under atmospheric conditions, which was previously considered infeasible. Photoautotrophic H 2 production has important implications for assessing ecological and algae-based photolysis.

[FeFe]- and [NiFe]-hydrogenase diversity, mechanism, and maturation

“…Phylogenetic analyses indicate that the H-cluster domain of algal [FeFe]-hydrogenase is not likely to be ancestral, rather it is likely that the ancestral enzyme had a single ferredoxin binding domain at the N-terminus which was lost when these genes were laterally transferred to algae [32]. The simple algal enzyme containing only the Hcluster is thought to function during the fermentation of carbohydrate reserves [45,46] although photosynthetic H 2 production was recently demonstrated under fully aerobic conditions in the alga Chlorella vulgaris [47].…”

Photosynthetic Microorganisms

“…Photosynthetic microorganisms have the genetic, metabolic, and enzymatic characteristics to produce hydrogen under anaerobic and limited aerobic conditions (Hwang et al 2014). The unicellular green algal species C. reinhardtii is one of the well-known hydrogen-producing algae Melis and Happe 2001;Girbal et al 2005).…”

Microoxic Niches within the Thylakoid Stroma of Air-Grown Chlamydomonas reinhardtii Protect [FeFe]-Hydrogenase and Support Hydrogen Production under Fully Aerobic Environment

“…In further support of this, recent reports have suggested that [FeFe]-hydrogenase is capable of aerobic activity in strains of Chlorella. It was shown that Chlorella vulgaris could maintain hydrogen production under atmospheres of 21% (Hwang et al, 2014) or 15% (Chader et al, 2009) oxygen. The active pool of hydrogenase was estimated at ;30 units per mg of dry weight (Hwang et al, 2014).…”

“…It was shown that Chlorella vulgaris could maintain hydrogen production under atmospheres of 21% (Hwang et al, 2014) or 15% (Chader et al, 2009) oxygen. The active pool of hydrogenase was estimated at ;30 units per mg of dry weight (Hwang et al, 2014). Last, in a recent paper by Godaux et al , the authors claim that in a transition from dark anoxia to light, high rate of hydrogen production decreased to lower rate, before the onset of oxygen accumulation.…”