Hydrogen photoproduction

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Even entrapment of entire cells within reversed micelles without loss of their functionality has been achieved. For example, mitochondria and bacteria (Actinobacter cal-coaceticus, Escherichia coli, Corynebacterium equi) have been successfully solubilized in a microemulsion consisting of isopropyl pahnitate, polyoxyethylene sorbitan trioleate [162], Enhanced hydrogen photoproduction by the bacterium Rhodopseudomonas sphaeroides or by the coupled system Halobacterium halobium and chloroplasts organelles entrapped inside the aqueous core of reversed micelles with respect to the same cells suspended in normal aqueous medium has been reported [183,184],... 

Ashokkumar M (1998) An overview on semiconductor particulate systems for photoproduction of hydrogen. Int J Hydrogen Energy 23 427-438... 

Mau AWH, Huang CB, Kakuta N, Bard AJ, Campion A, Eox MA, White JM, Webber SE (1984) Hydrogen photoproduction by Nafion/cadmium sulfide/platinum films in water/sulfide ion solutions. J Am Chem Soc 106 6537-6542... 

At present, several stable photocatalytic systems for production of hydrogen from water and organic compounds are made of semiconducting oxides and suitable proton reducing catalyzer. An efficient electron transfer between inorganic semiconductor and bacterial hydrogenase was shown to result in hydrogen photoproduction. 

PHOTOPRODUCTION OF HYDROGEN BY INORGANIC SEMICONDUCTOR Ti02 - HYDROGENASE MODEL SYSTEM... 

A. A. Krasnovsky, G. P. Brin, V. V. Nikandrov (1976) Oxygen photoreduction and hydrogen photoproduction on inorganic photocatalysts. Dokl. Acad Nauk. SSSR (Russ.), 229 990-993... 

N. A. Worin, T. Lissolo, A. Colbeau, P. M. Vignais (1996) Increased hydrogen photoproduction by Rhodobacter capsulatus strains deficient in uptake hydrogenase, J. Mar. Biotechnol., 4 28-33... 

E. Hustede, A. Steinbuchel, H. G Schlegel (1993) Relationship between the photoproduction of hydrogen and the accumulation of PHB in non-sulphur purple bacteria, Appl. microbiol. Biotechnol., 39 87-93... 

Before the consideration of the potential of technological methods in improvement of biological hydrogen photoproduction some definitions should be done. 

Several strategies for maximization of hydrogen photoproduction with different final targets are applicable. 

The rate of H2 production by one unit of photobioreactor s volume is not useful for estimation of strain capabilities or for measurements of efficiency of light energy conversion. However, it is useful unit of measurements for optimization of hydrogen production by particular photobioreactor. From practical point of view it does not matter how much cells are in the photobioreactor or how much hydrogen is produced by one unit of illuminated surface. The rate of hydrogen production by the whole photobioreactor is of first importance. For a comparison of different photobioreactors it is better to express rate of hydrogen photoproduction per unit of its volume. So, it is practical unit for estimation of actual hydrogen photoproduction. 

Batch cultures are the cultures without an input of fresh medium and an output of cultural broth. Batch cultures are very simple in realization and widely used for estimation of the potential of different strains in hydrogen photoproduction or for study of environmental factors influence on the process [for reference, see Roha et al., 2001 Akkerman et al., 2002],... 

High rates of hydrogen photoproduction were recorded with application of this regime of cultivation (Tab. 1). 

Table 1. Maximum hydrogen photoproduction by batch cultures or resting cells of purple bacteria...

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