Molecular hydrogen from bacteria

Russian researchers revealed that Rhodobacter sphaeroides bacteria can be a source of molecular hydrogen, an ecologically friendly fuel. Scientists studied various strains of the mentioned microorganism and demonstrated that hydrogen emission rate depended on pigmentation of cells. Less pigmented strains can be a promising source of molecular hydrogen. A search for new alternative energy sources is listed among burning problems of modern life. Hydrogen as a possible alternative fuel is quite promising – hydrogen engines emit only water vapours instead of exhaust gases, in other words, they are harmless for any environment. Moreover, hydrogen is a renewable energy resource – there are several techniques for this gas’s production. Among most popular techniques of hydrogen production we should mention steam methane reforming, in other words, heating mixture of water vapours with methane for hydrogen production.

These days commercial hydrogen production results in carbon dioxide emissions, which enhances greenhouse effect in Earth’s atmosphere. There are some techniques, which allow hydrogen production without harming our environment – using various bacteria for this purpose is one of such techniques. Purple bacteria Rhodobacter sphaeroides can become popular hydrogen producers, since they have a variety of metabolic pathways, when energy can be obtained either from sunlight, or from various organic substances. When these organisms use organic matter (glucose, lactate, organic acids) for life, they produce molecular hydrogen.

Scientists from the Institute of Fundamental Problem of Biology have paid close attention to the ability of purple bacteria Rhodobacter sphaeroides to emit hydrogen as a metabolite. Hydrogen emission rate appeared to depend on two factors: number of bacteria in a bioreactor, and intensity of a light beam, required for performing photosynthesis. Bacteria tend to increase hydrogen emission, when light intensity grows, but they stop at some threshold and react only by protective pigment production. Pigment allows these organisms to become less sensitive to light, and hydrogen production rate stops growing.

Russian scientists suggested a means for eliminating this effect. They have worked with a genetically modified strain of Rhodobacter sphaeroides, which had a damaged peripheral light-harvesting antenna complex. Another way of preventing bacteria from synthesizing protective pigments was growing microorganisms on a nutrient medium, which lacked nitrogen – this also troubles pigment synthesis. Experiments demonstrated that bacteria with low pigment concentration produced hydrogen much faster, than their wild-type relatives. Hydrogen-producing bacteria are a promising technology. Various types of “bacterial batteries” exist these days – living cells produce electricity, for instance, while “eating” sugar syrup. These systems are not powerful enough – their energy feeds as little as an IPod, but sometimes researchers would build an engine, based upon genetically modified bacteria, which emit molecular hydrogen. In this case petrol stations will sell sugar instead of gasoline.

Anna Kizilova