Sustained hydrogen production from cyanobacteria in the presence of oxygen

Oct 18, 2012
Sustained hydrogen production from cyanobacteria in the presence of oxygen
PNNL scientists Eric Hill and Leo Kucek compare culturing conditions in samples generated from a novel photobioreactor designed at PNNL.

(Phys.org)—As society's demand for renewable energy continues to grow, hydrogen (H2) is appealing because it's carbon-neutral, portable, clean, and simple. However, producing it inexpensively and in sufficient amounts without using fossil fuels remains a challenge.

Scientists at Pacific Northwest National Laboratory recently made a significant step toward meeting that challenge by achieving uninterrupted, sustained H2 production from a photosynthetic microorganism for more than 100 hours in the presence of oxygen gas (O2). Apparent O2 inhibition of H2 production in traditional cultivation systems has resulted in the long-held belief that sustained H2 during photosynthesis was not possible.

The PNNL team grew cultures of Cyanothece sp. ATCC 51142, a -fixing , in a specially designed photobioreactor in which the light environment and composition of dissolved nutrients and could be rigorously controlled and monitored.

Using this approach, PNNL scientists were able to provide the microbes with favorable conditions needed to produce H2 continuously without significant photodamage or decay in required .

The results not only demonstrate that uninterrupted H2 production in unicellular can be achieved over a number of days but indicates the feasibility of "direct biophotolysis" with sunlight and water serving as the primary substrates for H2 production. That is, when cells "split" water in photosynthesis, some of the molecular products can be directly used to make H2. Furthermore, this occurs even though O2 is being produced, which typically inhibits the enzymes producing H2.

Detection of concomitant production of both H2 and O2 by N-deprived Cyanothece 51142 cultures in the light.

According to Dr. Alex Beliaev, a PNNL and senior author of the paper, which was published in mBio, "Our study provides an important insight into the photophysiology of light-driven hydrogen production by photoautotrophic microorganisms. It also has significance for biotechnology-the sustainability of our process is a solid foundation for developing an effective, renewable, and economically efficient bio-hydrogen production process."

Using a novel photobioreactor designed and built at PNNL, the scientists grew the bacterial cultures under conditions where an enzyme (nitrogenase) that can produce H2 was induced. occurred when conditions were shifted so that the normal substrate for nitrogenase (N2 gas) was not present. The ability to monitor and control gas and light input into the system afforded high-resolution physiological details, opening a window on the relationship between O2 evolution and H2 production in the light for unicellular cyanobacteria.

The scientists are planning 'omics studies and measurements to identify what the cells are doing at the molecular and genetic level to prevent the inhibition by O2

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More information: MR Melnicki, GE Pinchuk, EA Hill, LA Kucek, JK Fredrickson, AE Konopka, and AS Beliaev. 2012. "Sustained H2 Production Driven by Photosynthetic Water Splitting in a Unicellular Cyanobacterium." mBio 3(4):e00197-12. DOI: 10.1128/?mBio.00197-12

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loneislander
1 / 5 (2) Oct 18, 2012
"...hydrogen (H2) is appealing because it's carbon-neutral, portable, clea..."

I'm not going to point out the flaw in that but it should be very obvious to those who post these articles.
Chromodynamix
not rated yet Oct 19, 2012
Hydrocarbon is a single element dontchaknow :p
Mike_Massen
1 / 5 (1) Oct 19, 2012
Even if free H2 is too expensive to use...

Its not 'portable' and its not 'simple' an engine running H2 wont last long unless its specially designed for it.

These guys in the article and their hydrogen adherents really need to do an end to end fully costed thermodynamic analysis.
Shakescene21
not rated yet Oct 19, 2012
@Loneislander-
If you read the article carefully, you will understand that this technology produces H2 in a carbon-neutral manner. Cyanobacteria utilize sunlight as the energy source to split water and generate H2 which can be collected and used as fuel.
antialias_physorg
5 / 5 (1) Oct 19, 2012
Its not 'portable' and its not 'simple' an engine running H2 wont last long unless its specially designed for it.

Those hydrogen trucks must be an illusion, then. (Or that 240km hydrogen pipeline in germany along the Ruhr which has been in operation since before WWII)

And our wonderful material graphene seems to inhibit embrittlement of metal with just a few layers.

These guys in the article and their hydrogen adherents really need to do an end to end fully costed thermodynamic analysis.

Do an end-to-end cost of thermodynamic analysis for other fuels INCLUDING cost of cleanup. You'll be surprised which comes out ahead.
Mike_Massen
1 / 5 (1) Oct 20, 2012
@antialias_physorg
Brave words but, no substance !

1. Do you believe these trucks run 100% on H2 & never run on
other fuels, subsidy ?
1.1 How far can they travel on a 'fill' & cost per Km ?
2. Do you believe the H2 pipeline is only fuel, how much
tonnage does it carry for chemical feedstocks ?
3. Has graphene already been used in transport, at what scale ?
4. When will graphene be tested in full production environment ?
5. Have you assessed costs of an H2 explosive cleanup ?

Has anyone on this list ever compared end to end thermodynamic calculation of H2 vs existing diesel fuels supply chain & factored in all the probabilistic risk assessments ?

Other than uneconomical government subsidies & political directives one has to wonder why all energy companies dont automatically progress to the most efficient thermodynamic solutions for the long term ?

? hmmm ?

Hey that's probably why H2 is NOT a primary focus as any sort of useful or safe transport fuel... !

Cheers

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