1,721,200 research outputs found
Understanding regulation in complex environments: a route to enhance photosynthetic light-reactions in microalgae photobioreactors
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Response to different illumination in Nannochloropsis gaditana, a algal candidate for biofuels production.
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Potential of microalgae biomass for the sustainable production of bio-commodities
Full text linkHuman activities are causing major negative environmental impacts, and the development of sustainable processes for production of commodities is a major urgency. Plant biomass represents a valuable alternative to produce energy and materials, but exploiting present crops for commodities production would however require massive resources (i.e. land, water and nutrients), raising serious sustainability concerns. In addition to efforts to improve plant, land and resource use efficiency, it is thus fundamental to look for alternative sources of biomass to complement crops. Microalgae are unicellular photosynthetic organisms that show a huge, yet untapped, potential in this context.
Microalgae metabolism is powered by photosynthesis and thus uses sunlight, a renewable energy source, and the exploitation of microalgae-based products has the potential to provide a beneficial environmental impact. These microorganisms have the ability to synthesize a wide spectrum of bioactive compounds, with many different potential applications (e.g. nutraceutics/pharmaceutics and biofuels). Several, still unresolved, challenges are however present such as the lack of cost-effective cultivation platforms and biomass-harvesting technologies. Moreover, the natural metabolic plasticity of microalgae is not optimized for a production at scale, and low biomass productivity and product yields affect competitiveness. Tuning microalgae metabolism to maximize productivity thus represents an unavoidable challenge to reach the theoretical potential of such organisms
Identification of key residues for pH dependent activation of violaxanthin de-epoxidase from Arabidopsis thaliana.
Full text linkPlants are often exposed to saturating light conditions, which can lead to oxidative stress. The carotenoid zeaxanthin, synthesized from violaxanthin by Violaxanthin De-Epoxidase (VDE) plays a major role in the protection from excess illumination. VDE activation is triggered by a pH reduction in the thylakoids lumen occurring under saturating light. In this work the mechanism of the VDE activation was investigated on a molecular level using multi conformer continuum electrostatic calculations, site directed mutagenesis and molecular dynamics. The pK(a) values of residues of the inactive VDE were determined to identify target residues that could be implicated in the activation. Five such target residues were investigated closer by site directed mutagenesis, whereas variants in four residues (D98, D117, H168 and D206) caused a reduction in enzymatic activity indicating a role in the activation of VDE while D86 mutants did not show any alteration. The analysis of the VDE sequence showed that the four putative activation residues are all conserved in plants but not in diatoms, explaining why VDE in these algae is already activated at higher pH. Molecular dynamics showed that the VDE structure was coherent at pH 7 with a low amount of water penetrating the hydrophobic barrel. Simulations carried out with the candidate residues locked into their protonated state showed instead an increased amount of water penetrating the barrel and the rupture of the H121-Y214 hydrogen bond at the end of the barrel, which is essential for VDE activation. These results suggest that VDE activation relies on a robust and redundant network, in which the four residues identified in this study play a major role
HEAT DISSIPATION IN THE MOSS PHYSCOMITRELLA PATENS: LESSONS on MECHANISM and EVOLUTION OF PROTECTION MECHANISMS UPON LAND COLONIZATION
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