Hydrogen production by phososynthetic bacteria

A two-stage, two-organism process for biohydrogen from glucose

“…This was suggested by a relatively low rate of H2 production observed for the positive control. This may be attributed to the use of fluorescent light, whereas tungsten/halogen lamps are preferable due to the emission of wavelengths in the range of 800 and 850 nm, corresponding to the absorption maxima of bacteriochlorophylls [4]. The use of an improved light source (tungsten; 250 µ/m2/s) could permit higher rates of substrate removal than those reported here, but the high nitrogen content would still prevent photoproduction of H2.…”

“…This method was used to prepare food processing wastewater and sewage sludge for use as fermentation feed [17]. Alternatively, classical deionisation techniques could potentially remove NH 4 + with some selectivity, but either approach would add significant process costs.…”

“…Practical fermentation yields tend to be around 2 mol H2 per mol hexose while yields approaching 4 mol/mol have been achieved using thermophilic fermentation [5]. Reported photoheterotrophic yields exceed 80% [4]. (Overall scheme) In reactor 1, E. coli HD701 (hydrogen overproducing strain) ferments glucose to produce H2.…”

“…(2) Photoheterotrophy : 2CH3COOH + 4H2O −h→ 8H 2 + 4CO2. [4] (3) Eqs. (2) and (3) describe an ideal situation in which all carbon substrate is processed along the appropriate pathways and none is diverted to the formation of biomass or alternative metabolites.…”

“…Experimental yields for H2 production from organic acids by Rhodobacter spp. can approach 100% [4,19]. H2 is produced as a by-product of the nitrogenase system, which functions in the fixation of N2 as ammonia, to provide a growth advantage under nitrogen limitation.…”