The photobiocatalytic system: Inorganic semiconductors coupled to bacterial cells

Abstract

Considering the evolutionary pathways of solar energy conversion, we suggested that some mineral components of the earth's crust might have been capable of electron phototransfer coupled to the metabolic chains of primary heterotrophic cells. We observed a peculiar type of this process when light‐exposed particles of titanium dioxide or some other minerals initiated an electron transfer from organic electron donors to Clostridium butyricum bacterial cells, with hydrogen being evolved as a result of intra‐ and extracellular activity of hydrogenase. The coupling of mineral photocatalysts to bacterial cells may be regarded as a way to create a new type of photobiocatalytic system.

Application to Photocatalytic H2 Production of a Whole‐Cell Reaction by Recombinant Escherichia coli Cells Expressing [FeFe]‐Hydrogenase and Maturases Genes

“…An alternative approach for photocatalytic H 2 production by an inorganic-bio hybrid photocatalyst is the use of whole cells as ab iocatalyst in place of purified hydrogenases.T he advantage of this approach is not only that whole cell catalyst is easier to obtain, but also that its stability is much higher than the purified enzymes.S ome laboratories have achieved H 2 production by using TiO 2 and Clostridium butylicum cells in combination with the electron mediator methylviologen (MV 2+ ), [6] or by using Bi 2 O 3 or dye-sensitized TiO 2 and ap hotosynthetic bacterium Rhodopseudomonas capulata in combination with MV 2+ . [7] Thes emiconductor/MV 2+ /bacterial cell system has the advantage that the cells that serve as biocatalysts can be easily prepared by harvesting cells from culture without the need for manipulations such as cell disruption and protein purification.…”

Application to Photocatalytic H2 Production of a Whole‐Cell Reaction by Recombinant Escherichia coli Cells Expressing [FeFe]‐Hydrogenase and Maturases Genes

“…We investigated the direct application of this recombinant strain for photocatalytic H 2 production ( Figure 1). [8] E. coli is the most commonly used microorganism for genetic engineering because of its well-characterized genomic and metabolic functions and its rapid cell growth on awide range of carbon sources.These characteristics of E. coli cells are an advantage for the preparation of the whole-cell biocatalyst compared to other microorganisms previously reported, such as C. butylicum [6] or R. capulata. Notably, among the three classes of hydrogenases,t he [FeFe]-hydrogenases show the highest turnover numbers and tend to exhibit superior rates of H 2 formation.…”

“…One type of known H 2 -forming biocatalysts,t he hydrogenases,c atalyzes both oxidation of H 2 into protons and reduction of protons to H 2 when combined with an electron acceptor/donor.T he hydrogenase enzymes are classified into three groups according to the composition of metals in their catalytic centers:[ Fe]-hydrogenase,[ NiFe]hydrogenase,a nd [FeFe]-hydrogenase. An alternative approach for photocatalytic H 2 production by an inorganic-bio hybrid photocatalyst is the use of whole cells as ab iocatalyst in place of purified hydrogenases.T he advantage of this approach is not only that whole cell catalyst is easier to obtain, but also that its stability is much higher than the purified enzymes.S ome laboratories have achieved H 2 production by using TiO 2 and Clostridium butylicum cells in combination with the electron mediator methylviologen (MV 2+ ), [6] or by using Bi 2 O 3 or dye-sensitized TiO 2 and ap hotosynthetic bacterium Rhodopseudomonas capulata in combination with MV 2+ . [3] More recently,visible light-driven H 2 production has been achieved with dye-sensitized TiO 2 and [NiFeSe]-hydrogenase, [4] and with mercaptopropionic acid-capped CdTen anocrystals or CdS nanorods in combi-nation with recombinant clostridial [FeFe]-hydrogenase.…”

Excited chlorophyll and related problems

“…Recently, we observed the possibility of cou- piing of TiO 2 particles with Clostridia cells (via reversibly photoreduced methyl viologen) which can diffuse through cell walls to the hydrogenase localized inside Clostridia cells leading to hydrogen photoproduction with quantum yield of up to 10% (Krasnovsky and Nikandrov 1987) (see Fig. 5).…”