H2 Photoproduction

H2 Photoproduction.—The development of sacrificial H2-evolving photosystems, in which Hi production is at the expense of consuming some added 

Kraljic, M. Mintas, L. Klasinc, F. Ranogajec, and H. Guesten, Noup. J. CTiim., 1983,7,239. 

Direct excitation of in aqueous or methanolic solution with u.v. light 

Zengerle, Helv. Qiim. Acta, 1983, 66, 2652. 

Richoux, Photo neration of Hydro n , ed. A. Harriman and M. A. West, Academic lYess, London, 1982, p. 39. 

Conventional jitoto ysterns for the visible light induced 

Metalloporphyrin based photosystems have been reviewed and it 

The most popular electron relay in these photosystems continues to be methyl viologen although it is well established that this material is unstable with respect to hydrogenation 

In addition to the photosensitised evolution of H2 the above systems are readily adapted for other useful chemical processes. 

---

The ability of H2 photoproduction as a result of photoinduced electron transfer from Ti02 particles to hydrogenase was demonstrated in 1976 by Krasnovsky at al. [1], H2 was produced under irradiation of Ti02 suspension containing hydrogenase from T. roseopersicina,... 

Figure 1. H2 photoproduction by Ti02 - hydrogenase model system.

The activation of H2 photoproduction by CaCl2 was observed not only with Tris buffer as an electron donor but with sucrose, dithiothreitol, or methanol as well. BaCl2, like CaCl2, enhanced the rate of H2 photoproduction by a factor of about 30. Chlorides of monovalent metals increased the reaction rate in the system Tris-Ti02-hydrogenase insignificantly [2],... 

M. Kern, W. Klipp, J. H. Klemme (1994) Increased nitrogenase-dependent H2 photoproduction by hup mutants of Rhodospirillum rubrum, Appl. Environmental Microbo., 60 1768-1774... 

In this paper we describe an easy, reproducible, and fast procedure for obtaining PSI-enriched particles by a non-detergent method from the thermophilic cyanobacterium Phormidium lamirtosum. These particles showed a PSI activity (ascorbate/DCPIP MV) of up to 200 (imole 02 taken up per mg chlorophyll per h, and negligible PSII activity (H20 DMBQ or ferricyanide). We also present evidence on the feasibility of H2 photoproduction and phosphoribulokinase photoactivation mediated by such PSI particles coupled to hydrogenase or to a Fd/TRX system. 

Table 1. A summary of the currendy known genes in the unicellular green alga, including Chlamydomonas reinhardtii, which are involved in the process of H2 production or in the cellular metabolism related to H2 photoproduction (adapted from Ref. 162.)...

Mus, F., Cournac, L., Cardettini, V., Caruana, A. and Peltier, G. 2005. Inhibitor studies on non-photochemical plastoquinone reduction and H2 photoproduction in Chlamydomo-nas reinhardtii. Biochim. Biophys. Acta 1708, 322-332. 

Tsygankov, A.A., Borodin, V.B., Rao, K.K.., Hall, D.O. (1999). H2 photoproduction by batch culture of Anabaena variabilis ATCC 29413 and its mutant PK84 in a photobioreactor. Biotechnol. Bioeng. (in press - Production number BB-2884). 

Factors affecting H2 photoproduction by purple bacteria are described in this minireview. Based on comparison of maximum H2 photoproduction rates by suspension and immobilized cultures, it is concluded that immobilized culture is more attractive for application. Possibility for scaling up of photobioreactors with immobilized purple bacteria is discussed. 

SPECIFIC RATE OF H2 PHOTOPRODUCTION BY SUSPENSIONS OF PURPLE BACTERIA AND INFLUENCE OF ENVIRONMENTAL FACTORS... 

Together with basic investigations, intensive attempts were undertaken to apply the potential of purple bacteria for commercial H2 photoproduction (for review see Sasikala et al., 1993). The most important parameter for industrial H2 production by the system is the rate of H2 evolution per unit of illuminated surface. It depends on the specific H2 evolving activity of purple bacteria (fundamental property), on the concentration of an active biomass (technological parameter) and on the surface-to-volume ratio (construction parameter). 

From an evaluation of the highest specific rates of H2 photoproduction by different purple bacteria using various organic substrates published by different authors, one notes little success in acceleration of this important parameter during the last two decades (Table 1). 

THE SPECIFIC RATES OF H2 PHOTOPRODUCTION BY DIFFERENT PURPLE BACTERIA DATA LISTED CHRONOLOGICALLY... 

The specific rate of H2 photoproduction by purple bacteria depends on the total activity of nitrogenase in the cells and on the environmental factors ... 

This minireview does not cover all aspects of H2 photoproduction by purple bacteria. However, based on data reviewed here, we can formulate some requirements for bacteria as possible elements of a system for photobiological H2 production as well as for photobioreactors incorporating purple bacteria. 

Decreased quantity of pigments. Suspensions and immobilized cells of purple bacteria for H2 photoproduction with decreased quantity of pigments (but with very effective photosynthetic apparatus) allow for use of higher concentrations of biomass and, consequently, higher rates of H2 photoproduction per unit of volume. 

---