Microalgal Hydrogen Production

Abstract

Microalgae, as facultative aerobic organisms, convert solar energy to produce biohydrogen under anaerobic condition. Biohydrogen is a kind of ideal clean and renewable energy source with great commercial potential. Many endeavors have been focused on improving the biohydrogen yields by various means. Here, the research history of hydrogen production by microalgae (including cyanobacteria and green algae), the characteristics of nitrogenase and hydrogenase, the mechanisms of hydrogen production, the technological progress, and the application of enzymatic, genetic, and metabolic engineering methods to improve hydrogen production by microalgae are reviewed. In addition, the regulation of anaerobic metabolisms of Chlamydomonas reinhardtii after the disruption of key enzymes functioning in the fermentative pathways is discussed. Finally, the main challenges and obstacles facing the more efficient production and commercialization of hydrogen production from microalgae in the future are proposed.

Advances in Whole‐Cell Photobiological Hydrogen Production

“…Whole‐cell biocatalyst hybrids for H 2 production (cellular semiartificial photosynthesis) have attracted increasing attention due to their potential to combines the best of natural photosynthesis and artificial photosynthesis. [ 5,6b,108 ] As cellular semiartificial photosynthesis can achieve the goal of reasonable and efficient H 2 production, it is a crucial part for the future development of sustainable energy systems.…”

“…Nutrient deprivation, such as sulfur (S), nitrogen (N), phosphate (P), magnesium (Mg) deprivation, light deprivation, and the addition of chemical PSII inhibitor, belongs to this kind of strategy. In addition to the strategy by suppression of O 2 production is the strategy by removal of O 2 , in which by purging inert gases (N 2 , Ar) or adding chemical reagents (glucose oxidase, ascorbic acid, and NaHSO 3 ), we can scavenger O 2 , thereby forming an anaerobic environment for photobiological H 2 production [6a,12,15] …”

“…Nowadays, biological H 2 production is typically realized by the use of hydrogenase‐expressed microorganisms, such as green algae, cyanobacteria, purple photosynthetic bacteria, and some heterotrophic bacteria with hydrogenase, or isolated hydrogenase directly. [ 6 ] Using microorganisms as a whole‐cell biocatalyst to synthesize H 2 is simpler and more robust and therefore has more practical application prospects. At present, large‐scale biological H 2 production is basically produced through microorganisms’ anaerobic fermentation, also known as dark fermentation.…”

“…[ 8 ] Green algae have the potential to express [FeFe]‐hydrogenases that have high activity for catalyzing H 2 production. Cyanobacteria usually possess [NiFe]‐hydrogenases as well as nitrogenase that can catalyze nitrogen (N 2 ) fixation and produce H 2 as a byproduct [6a] . Nevertheless, green algae and cyanobacteria (hereinafter collectively termed microalgae) have photosystem II (PSII) which absorbs solar energy to photolyze water and produce oxygen (O 2 ) that is harmful to hydrogenase and nitrogenase, inhibiting H 2 production with cultured microalgae.…”

Transcription of the Hydrogenase Gene during H2 Production in Scenedesmus Obliquus and Chlorella Vulgaris

“…[FeFe]-hydrogenase (Wang et al 2020). However, the scarce information available on gene and enzyme sequences is a limiting factor for their potential application.…”