[FeFe]-hydrogenases as biocatalysts in bio-hydrogen production

© 2016, Accademia Nazionale dei Lincei. [FeFe]-hydrogenases catalyse H2 production at exceptionally high turnover numbers (up to 104s−1). They are found in a variety of strict or facultative anaerobic microorganisms, such as bacteria of the genus Clostridium, Desulfovibrio, Thermotoga, and eukaryotes ranging from unicellular and coenobial green algae to anaerobic fungi, ciliates and trichomonads. Key to their activity is an organometallic centre, the H-cluster that cooperates tightly with the protein framework to reduce two protons into molecular hydrogen. The assembly of the catalytic site requires a specialised cellular mechanism based on the action of three other enzymes, called maturases: HydE, HydF and HydG. Recent advancements in the recombinant production of [FeFe]-hydrogenases have provided leaps forward in their exploitation in H2 production for clean energy storage. [FeFe]-hydrogenases have been used in several fermentative approaches where microorganisms are engineered to overexpress specific [FeFe]-hydrogenases to convert low-cost materials (e.g. wastes) into H2. [FeFe]-hydrogenases have also been proven to be excellent catalysts in different in vitro devices that can produce hydrogen directly from water, either via water electrolysis or via light-driven mechanisms, thus allowing the direct storage of solar energy into H2

Oxygen Stability in the New [FeFe]-Hydrogenase from Clostridium beijerinckii SM10 (CbA5H)

© 2016 American Chemical Society. The newly isolated Clostridium beijerinckii [FeFe]-hydrogenase CbA5H was characterized by Fourier transform infrared spectroscopy coupled to enzymatic activity assays. This showed for the first time that in this enzyme the oxygen-sensitive active state Hox can be simply and reversibly converted to the oxygen-stable inactive Hinact state. This suggests that oxygen sensitivity is not an intrinsic feature of the catalytic center of [FeFe]-hydrogenases (H-cluster), opening new challenging perspectives on the oxygen sensitivity mechanism as well as new possibilities for exploitation in industrial applications

Atypical effect of temperature tuning on the insertion of the catalytic iron?sulfur center in a recombinant [FeFe]-hydrogenase

© 2015 The Protein Society. The expression of recombinant [FeFe]-hydrogenases is an important step for the production of large amount of these enzymes for their exploitation in biotechnology and for the characterization of the protein-metal cofactor interactions. The correct assembly of the organometallic catalytic site, named H-cluster, requires a dedicated set of maturases that must be coexpressed in the microbial hosts or used for in vitro assembly of the active enzymes. In this work, the effect of the post-induction temperature on the recombinant expression of CaHydA [FeFe]-hydrogenase in E. coli is investigated. The results show a peculiar behavior: the enzyme expression is maximum at lower temperatures (20C), while the specific activity of the purified CaHydA is higher at higher temperature (30C), as a consequence of improved protein folding and active site incorporation

Special enzymes, like "Easter Eggs" with wonderful functions for biotechnology

We guess you know very well what an Easter Egg is in a video game: a special surprise that was hidden in a secret area or a bonus object. We discovered [Morra et al., 2016a, check Bibliography for info and link to this original scientific paper and to other papers cited] a similar “Easter Egg” in a protein that functions in a very useful bacterium, and this suggested us how proteins and enzymes can contribute to a bio-sustainable future. But first let us introduce you the scientific background and the context. Continua a leggere..

Electron transfer and H2 evolution in hybrid systems based on [FeFe]-hydrogenase anchored on modified TiO2

© 2016 Hydrogen Energy Publications LLC The hybrid systems composed by [FeFe]-hydrogenase anchored to the surface of three distinct types of TiO2 (anatase) have been investigated using Electron Paramagnetic Resonance (EPR) spectroscopy in dark and under illumination. The three supports were bare TiO2 nitrogen doped TiO2 (N-TiO2) and a sub-stoichiometric form of the same oxide (TiO2−x) exhibiting blue color. EPR spectroscopy has shown that the electrons photogenerated by irradiation of the supports are stabilised by the solid forming Ti3+ paramagnetic ions while, in the case of the hybrid systems electrons are scavenged by the anchored protein becoming available for H+ reduction. The ability of the three hybrid systems in hydrogen production under solar light illumination has been compared. The formation of H2 is higher for the system containing N-TiO2 (yellow) with respect to that based on the bare oxide (white) indicating that the visible light absorbed, due to the presence of N states, is actually exploited for hydrogen production. The system containing reduced blue TiO2, in spite of its deep coloration, is less active suggesting that a specific type of visible light absorption is needed to produce photoexcited electrons capable to interact with the anchored protein

Biohydrogen and biomethane production sustained by untreated matrices and alternative application of compost waste

© 2016 Elsevier Ltd Biohydrogen and biomethane production offers many advantages for environmental protection over the fossil fuels or the existing physical-chemical methods for hydrogen and methane synthesis. The aim of this study is focused on the exploitation of several samples from the composting process: (1) a mixture of waste vegetable materials (“Mix”); (2) an unmatured compost sample (ACV15); and (3) three types of green compost with different properties and soil improver quality (ACV1, ACV2 and ACV3). These samples were tested for biohydrogen and biomethane production, thus obtaining second generation biofuels and resulting in a novel possibility to manage renewable waste biomasses. The ability of these substrates as original feed during dark fermentation was assayed anaerobically in batch, in glass bottles, in order to determine the optimal operating conditions for hydrogen and/or methane production using “Mix” or ACV1, ACV2 or ACV3 green compost and a limited amount of water. Hydrogen could be produced with a fast kinetic in the range 0.02–2.45mLH2g−1VS, while methane was produced with a slower kinetic in the range 0.5–8mLCH4g−1VS. It was observed that the composition of each sample influenced significantly the gas production. It was also observed that the addition of different water amounts play a crucial role in the development of hydrogen or methane. This parameter can be used to push towards the alternative production of one or another gas. Hydrogen and methane production was detected spontaneously from these matrices, without additional sources of nutrients or any pre-treatment, suggesting that they can be used as an additional inoculum or feed into single or two-stage plants. This might allow the use of compost with low quality as soil improver for alternative and further applications