HYDROGEN-PRODUCTION FROM ORGANIC SUBSTRATES IN AN AEROBIC NITROGEN-FIXING MARINE UNICELLULAR CYANOBACTERIUM SYNECHOCOCCUS SP STRAIN MIAMI BG-043511

Synechococcus sp. strain Miami BG 043511 exhibits very high H-2 photop roduction from water, but the H-2 photoproduction capability is lost r apidly with the age of the batch culture. The decrease of the capabili ty coincides with the decrease of cellular glucose (glycogen) content. However, H-2 photoproduction capability can be restored by the additi on of organic substrates. Among 40 organic compounds tested, carbohydr ates such as glucose, fructose, maltose, and sucrose were effective el ectron donors. Among organic acids tested, only pyruvate was an effect ive electron donor. Among alcohols tested, glycerol was a good electro n donor, whereas ethanol was a poor but positive electron donor. These results demonstrate that this unicellular cyanobacterium exhibits a w ide 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 m mol of pyruvate, glucose, maltose, sucrose, fructose, and glycerol wer e 1.11, 0.62, 0.50, 0.47, 0.30, and 0.39 mu moles per mg cell dry weig ht per hour respectively. Therefore, this cyanobacterial strain may ha ve a potential significance in removing organic materials from the was tewater and simultaneously transforming them to H-2 gas, a pollution-f ree energy. The activity of nitrogenase, which catalyzes hydrogen prod uction, completely disappeared when intracellular glucose (glycogen) w as used up, but it could be restored by the addition of organic substr ates such as glucose and pyruvate. (C) 1994 John Wiley and Sons, Inc.