OPTIMIZING PHOTOHETEROTROPHIC H-2 PRODUCTION BY RHODOBACTER-CAPSULATUS UPON INTERPOSON MUTAGENESIS IN THE HUPL GENE

In Rhodobacter capsulatus, the hupL gene encoding the large subunit of the uptake-hydrogenase (Hup) enzyme complex was mutated by insertion of an interposon. The mutant neither synthesized an active hydrogenase nor grew photoautotrophically. Under conditions of nitrogen (N) limit ation, photoheterotrophic cultures of the wild type and the mutant evo lved H-2 by activity of the nitrogenase enzyme complex. When grown wit h glutamate as an N source and either D,L-malate or L-lactate as carbo n sources, the efficiency of H-2 production by the HupL mutant was hig her than 90%, whereas wild-type cultures exhibited efficiencies of 54% (with D,L-malate) and 64% (with L-lactate), respectively. With NH4+ a s the N source, efficiencies of H-2 production were 70% (mutant) and 5 2% (wild type).