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Hydrogen-Producing Bacteria Could Provide Clean Energy

Posted by timothy on from the for-my-motorhome-of-the-future dept.

Iddo Genuth writes "Scientists at the Agricultural Research Service (ARS) and North Carolina State University (NC State) have developed cooperatively a new 'green' technology which could lead to clean production of hydrogen from nitrogen-fixing bacteria."

6 of 57 comments (clear)

  1. A twosome. by Ostracus · · Score: 3, Informative

    Umm, two things.

    "Using a selecting agent to grow only these bacteria, the teams identified a gene that inactivates the bacteria's hydrogen uptake system so that all of the hydrogen produced is released. Because the bacterial cells cannot recycle the hydrogen, the hydrogen they produce can be captured and used as a fuel whose byproduct is water and heat"

    What effect does this have on the bacteria?

    Also it seems like two different stories. the first is about agricultural bacteria. The link to the website talks about heat-loving bacteria like near volcanoes.

    --
    Shai Schticks:"You don't make peace with friends, you make peace with enemies"
    1. Re:A twosome. by reverseengineer · · Score: 4, Informative
      It wouldn't necessarily have to have any impact on the bacteria themselves. The equation for biological nitrogen fixation is
      N2 + 8H+ + 8e- + 16 ATP 2NH3 + H2 + 16ADP + 16 Pi (where Pi is inorganic phosphate)

      Basically, nitrogen-fixing bacteria use an enzyme called nitrogenase to grab a nitrogen molecule (N2), donate electrons to the nitrogen molecule to break the triple bond, then bond protons to the nitrogen -3 ions to form stable ammonia, which the bacteria then incorporates into amino acids- the inorganic becomes organic. This requires a large amount of energy, supplied by a very large amount of ATP breaking apart. Notice that on the right side of the equation, hydrogen gas is produced. Normally, the bacterium reclaims this hydrogen through use of another enzyme. However, with the hydrogen uptake enzyme disabled, the bacteria should release this gas into the environment. I say "should" here because I will admit the possibility of something unforeseen happening.

      However, the basic equation does not call for molecular hydrogen as a reactant; it calls for protons, which can be found pretty freely in any aqueous environment. Just raise the bacteria in a slightly acidic enviroment, and they should have all the protons they could ever need. The bacteria already have an amazing symbiosis set up with the legume plants they live on, so really all humans need to put into the system is the effort to keep a bunch of bean plants alive (which is helped by the nitrogen-fixing bacteria on the roots that naturally provide fertilizer for the legumes). All humans would really need to put into the system is water, sunlight, and nitrogen gas. I think this is a really clever idea, actually.

      I wonder if it might also be possible to use engineered nitrogen-fixing bacteria for their ammonia in order to replace the Haber-Bosch process, which, while a triumph of industrial chemistry, is responsible for something like 1% of the world's energy use.

      --
      "FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
    2. Re:A twosome. by reverseengineer · · Score: 3, Informative

      Looks like I lost my arrow in the equation there. It should read:

      N2 + 8H+ + 8e- + 16 ATP -----> 2NH3 + H2 + 16ADP + 16 Pi

      One diatomic nitrogen, eight protons, eight electrons, and sixteen adenosine triphosphates form two ammonia, two diatomic hydrogen (which we'd like), sixteen adenosine diphosphate, and sixteen inorganic phosphate. The nitrogen comes from the atmosphere, the protons and electrons from the bacterium (the enzyme nitrogenase helps with providing electrons), and the ATP from the bacteria's metabolism, food for which comes courtesy the bacterium's symbiotic buddy, the legume.

      --
      "FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
    3. Re:A twosome. by reverseengineer · · Score: 4, Informative

      Looking deeper into it, I should note that the specific bacteria cited here, Thermotoga maritima, are not the sort to be found on the roots of legumes. Apparently, "The Future of Things" condensed two separate discoveries into one story. The NC State work is more about identifying hydrogen-producing bacteria, while the Agricultural Research Service work is about building on the NC State work to find suitable hydrogen-producing candidates in agriculturally significant bacteria, and then decoupling hydrogen reuptake to make hydrogen collection feasible. The thermotogales that the NC State professor cited is interested in are most definitely not agriculturally significant.

      Thermotogales are hyperthermophiles that live in places like hot springs, oceanic thermal vents, and the bottoms of oil wells. The processes involved are completely different- thermotogale bacteria are not nitrogen-fixers. They produce hydrogen as part of their basic metabolism. Humans, for example, produce water in their metabolism. We use oxygen as our terminal electron acceptor, so the oxygen we breathe and send to our cells gains some electrons, then quickly picks up some protons to form water. Thermotogales, however, live in an enviromnent with little oxygen, but lots of sulfur. They use sulfur as a terminal electron acceptor, and so produce hydrogen sulfide, H2S. If the available sulfur happens to be in a bound form, however, instead of producing hydrogen sulfide, they will produce lots and lots of hydrogen gas. Unfortunately, thermotogales are not very tolerant of oxygen and prefer to live in near-boiling water, so while there has been investigation into their industrial use, their suitability is far less than that of the common nitrogen-fixers.

      In contrast, rhizobial bacteria have a mutual arrangement in place with legumes that make them far more hardy. Most legumes grow nodules on their roots to serve as homes for nitrogen-fixing bacteria. The enzyme-catalyzed nitrogen fixation is ruined by oxygen, so the nodule provides an anoxic environment. The legume also provides a carbon source for the bacteria. In exchange, the bacteria provide bioavailable nitrogen compounds to the legume. So, while the rate of hydrogen production is less from nitrogen-fixers, the advantages of the symbiotic arrangement are such that if you wanted to make a biotech hydrogen generation facility, a greenhouse full of bean plants might be the way to go.

      --
      "FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
  2. Re:Still need sugars by reverseengineer · · Score: 4, Informative

    Actually, the bacteria they used has this aspect covered. From the MicrobeWiki (ridiculously informative, btw):

    Thermotogales are thermophilic or hyperthermophilic, growing best around 80C and in the neutral pH range (R. Huber et al., 2004). The salt tolerance of Thermotoga species varies greatly; while some display an extremely high salt tolerance, others are restricted to low-salinity habitats. This aerobic gram-negative organism is typically nonsporeforming and metabolizes several carbohydrates, both simple and complex, including glucose, sucrose, starch, cellulose, and xylan (EBI, 2003).

    (Bolding mine) So it eats cellulose and makes hydrogen. Mildly useful, I would say.

    --
    "FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
  3. Re:I assume the other byproduct is snake oil by russotto · · Score: 3, Informative

    I don't understand. What's going on at NCSU that they would provide so little detail for this release. How the hell do you covert hydrogen to methane?

    Add carbon monoxide. CO + 3H2 = CH4 + H2O This is Fischer-Tropsch. Biological organisms probably go through a rather convoluted set of steps, and start with CO2 rather than CO.