Patrick C. Hallenbeck

Bioengineering aspects of biophotolysis

Abstract The practical aspects of producing hydrogen by photosynthetic microorganisms are reviewed. Various alternative concepts for hydrogen production are discussed, both single and two-stage systems. The best developed process currently is based on nitrogen-fixing heterocystous blue-green algae which can produce hydrogen and oxygen simultaneously. Solar energy conversion to hydrogen efficiencies of 0.2% averaged over several weeks have been obtained with outdoor systems. Practical systems would require a ten-fold increase in conversion efficiencies. Also, systems which produce pure hydrogen are preferred. Photosynthetic bacteria are of near-term applications. A general design for a biophotolysis system is proposed consisting of vertically arranged, thin-walled glass tubes with an inert gas recirculated through the cultures for mixing and removal of hydrogen. Gas mass transfer considerations, energy utilization, and economics favour such a system.

Immunochemical evidence that nitrogenase is restricted to the heterocysts in Anabaena cylindrica

The question of whether the vegetative cells of Anabaena cylindrica synthesize nitrogenase under anaerobic conditions was studied by immunoferritin labelling of the Fe-Mo protein (Component I). Differentiating cultures, incubated under an argon atmosphere, were treated with DCMU 12 h following initiation of induction. DCMU inhibited photosynthetic O2 production, thus insuring strict anaerobic conditions, but had no effect on nitrogenase induction. Fe-Mo protein levels, as determined by rocket immunoelectrophoresis, increased 5-fold within 24h of DCMU treatment. Immunoferritin labelling of aldehyde fixed, ultrathin cryosections of anaerobically induced filaments showed that the Fe-Mo protein was restricted to the heterocyst. Ferritin labelling was shown to be specific by the following criteria: (a) substituting preimmune goat serum for the anti-Fe-Mo protein IgG prevented ferritin labelling; (b) ferritin-conjugated, non-homologous rabbit anti-goat IgG did not bind; (c) incubation of anti-Fe-Mo protein IgG treated sections with rabbit anti-goat IgG prior to the treatment with the ferritin label also prevented labelling. The results provide direct immunochemical evidence that nitrogenase is restricted to the heterocysts even under strictly anaerobic conditions.

Purification and properties of a peptic heme peptide from cytochrome c1.

Summary A novel purification procedure was devised to isolate a heme peptide from bovine cytochrome c 1 . The procedure was based on unique properties of some heme peptides and was capable of processing small quantities (∼ 100 n moles) of material with satisfactory yields. The dansyl reactions, two-dimensional thin layer chromatography, and electrophoresis demonstrated that the peptide was reasonably homogenous. The amino acid composition and spectral characteristics indicate a high degree of similarity with the peptic heme peptide of bovine cytochrom c .

Hydrogenase activity in the thermophile mastigocladus laminosus

Abstract Hydrogenase activity in the thermophilic cyanobacterium, Mastigocladus laminosus was studied both in vivo and in vivo hydrogen consumption required oxygen but not light, was about ten-fold higher than in mesophilic cyanobacteria, and was relatively insensitive to carbon monoxide. H 2 -supported acetylene reduction in reductant-limited cultures was a light-dependent, but O 2 -independent reaction. In vitro hydrogen evolution was unaffected by carbon monoxide, and this activity could be partially purified using a procedure developed for Anabaena cylindrica .