Microalgae: a green source of renewable H2 - research paper from MIT

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Microalgae: a green source of renewable H2 - a research paper from MIT, Dec 2000

Maria L. Ghirardi, Liping Zhang, James W. Lee, Timothy Flynn, Michael Seibert, Elias Greenbaum and Anastasios Melis

Abstract & Introduction

This article summarizes recent advances in the field of algal hydrogen production. Two fundamental approaches are being developed. One involves the temporal separation of the usually incompatible reactions of O2 and H2 production in green algae, and the second involves the use of classical genetics to increase the O2 tolerance of the reversible hydrogenase enzyme.
The economic and environmental impact of a renewable source of H2 are also discussed.

Hydrogen (H2) metabolism is primarily the domain of bacteria and microalgae. It occurs in many, taxonomically diverse, species, takes place by a variety of biochemical mechanisms and processes, and has many physiological adaptations1–4. Microbial H2 formation is catalysed by either nitrogenases or hydrogenases, enzymes that can only function under anaerobic conditions. Nitrogenases are used by certain cyanobacteria (blue–green algae) and photosynthetic bacteria, whereas green algae use hydrogenase(s) to photoevolve H2. Nitrogenase-catalysed H2 evolution has been examined as a means of producing H2 gas commercially5–8. However, this has limitations including the low catalytic turnover rate of the enzyme9,10 and the high energy requirement (two or more ATP molecules per electron transported11).

The H2 metabolism of green algae was discovered in the early 1940s by Hans Gaffron12. He observed that green algae (under anaerobic conditions) can either use H2 as an electron donor in the CO2-fixation process or evolve H2 in both dark and the light. These original observations were later extended to many other green algae including Chlamydomonas reinhardtii13–15, Chlorella fusca16 and Scenedesmus obliquus12,17. H2 production in eukaryotic green algae requires a period of several minutes to a few hours of anaerobic incubation in the dark14,18–20. This apparently induces the biosynthesis and/or activation of the reversible hydrogenase, and probably of other H2-metabolizing enzymes, and enables the cells to photoproduce H2.

Read more from the original paper (PDF)

Nature gave us oil from algae; perhaps we should try Nature's way again

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About Oilgae - Oilgae - Oil & Biodiesel from Algae has a focus on biodiesel production from algae while also discussing alternative energy in general. Algae present an exciting possibility as a feedstock for biodiesel, and when you realise that oil was originally formed from algae - among other related plants - you think "Hey! Why not oil again from algae!"