Photoconversion of Organic Substrates into Hydrogen Using Photosynthetic Bacteria.

摘要

Under nitrogen-limited conditions, photosynthetic bacteria photoconvert a wide variety of organic substrates nearly totally into H sub 2 and CO sub 2 . More than 98% of the chemical energy of defined organic compounds even from dilute solutions can be recovered as combustible energy of the H sub 2 produced. Not calculating the chemical energy input, radiant (solar) energy recoveries are approximately 5% over a wide range of incident light intensities. Batch cultures can photoproduce H sub 2 at rates of 175 ml per gram dry weight of cells per hour (equal to a volume of H sub 2 per equivalent volume of liquid medium every 4 to 6 hours) when incubated in saturating light. With periodic refeeding, rates remain constant for several weeks. In closed containers H sub 2 pressures of 735 psig can be generated. In principle, this pressure can be used to decrease storage volume of the gas, to move it through pipelines or to provide required process pressures. Alcohol stillage and food processing wastes are excellent photoconvertible substances. When non-photosynthetic bacteria synthesizing appropriate polysaccharases are included in co-culture with photosynthetic bacteria, cellulose and other polysaccharides can be converted to H sub 2 and CO sub 2 , albeit at low rates. Prospects for enhancing the photoconversion reactions of photosynthetic bacteria by environmental and genetic manipulations are discussed. (ERA citation 06:018277)