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Synechococus sp. strain Miami BG 043511 exhibits very high H(2) photoproduction from water, but the H(2) photoproduction capability is lost rapidly with the age of the batch culture. The decreases of the capability coincides with the decrease of cellular glucose (glycogen) content. However, H(2) photoproduction capability can be restored by the addition of organic substrates. Among 40 organic compounds tested, carbohydrates such as glucose, fructose, maltose, and sucrose were effective electron donors. Among organic acids tested, only pyruvate was an effective electron donor. Among alcohols tested, glycerol was a good electron donor. These results demonstrate that this unicellular cyanobacterium exhibits a wide substrate specificity for H(2) photoproduction but has a different substrate specificity compared to photosynthetic bacteria. The maximum rates of H(2) photoproduction from a 6-day-old batch culture with 25 mmol of pyruvate, glucose, maltose, sucrose, fructose, and glycerol were 1.11, 0.62, 0.50, 0.47, 0.30, and 0.39 micromoles per mg cell dry weight per hour respectively. Therefore, this cyanobacterium strain may have a potential significance in removing organic materials from the wastewater and simultaneously transforming them to H(2) gas, a pollution free energy. The activity of nitrogenase, which catalyzes hydrogen production, completely disappeared when intracellular glucose (glycogen) was used up, but it could be restored by the addition of organic substrates such as glucose and pyruvate. (c) 1994 John Wiley & Sons, Inc.

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