A kinetic study of hydrogen production by a Calvin-Benson-Bassham cycle mutant, PRK (phosphoribulose kinase), of the photosynthetic bacterium Rhodobacter capsulatus

In the purple non-sulfur photosynthetic bacteria, the Calvin-Benson-Bassham (CBB) cycle plays a role in maintaining intracellular redox balance under photoheterotrophic growth conditions, potentially consuming reductant and chemical input (ATP) that could be used for H-2 production by nitrogenase. Previous studies have shown Rhodobacter capsulatus JP91 to be a remarkable H-2 producer and in the present study a PRK, phosphoribulose kinase, knockout mutant of this strain was created in an attempt to further improve H-2 yield. Analysis of growth with different carbon sources showed that this mutant could only grow in acetate medium without, however, producing any H-2. A spontaneous mutant was recovered which had gained the ability to grow on glucose and produce H-2 with a yield that was 20-40% greater than the wild type, JP91 strain. Analysis shows that growth and hydrogen production are strongly linked with electrons from glucose mostly directed to H-2 production and biomass formation. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.