24 results found
Perin G, Gambaro F, Morosinotto T, 2022, Knowledge of regulation of photosynthesis in outdoor microalgae cultures is essential for the optimization of biomass productivity, Frontiers in Plant Science, Vol: 13, ISSN: 1664-462X
Microalgae represent a sustainable source of biomass that can be exploited for pharmaceutical, nutraceutical, cosmetic applications, as well as for food, feed, chemicals, and energy. To make microalgae applications economically competitive and maximize their positive environmental impact, it is however necessary to optimize productivity when cultivated at a large scale. Independently from the final product, this objective requires the optimization of biomass productivity and thus of microalgae ability to exploit light for CO2 fixation. Light is a highly variable environmental parameter, continuously changing depending on seasons, time of the day, and weather conditions. In microalgae large scale cultures, cell self-shading causes inhomogeneity in light distribution and, because of mixing, cells move between different parts of the culture, experiencing abrupt changes in light exposure. Microalgae evolved multiple regulatory mechanisms to deal with dynamic light conditions that, however, are not adapted to respond to the complex mixture of natural and artificial fluctuations found in large-scale cultures, which can thus drive to oversaturation of the photosynthetic machinery, leading to consequent oxidative stress. In this work, the present knowledge on the regulation of photosynthesis and its implications for the maximization of microalgae biomass productivity are discussed. Fast mechanisms of regulations, such as Non-Photochemical-Quenching and cyclic electron flow, are seminal to respond to sudden fluctuations of light intensity. However, they are less effective especially in the 1–100 s time range, where light fluctuations were shown to have the strongest negative impact on biomass productivity. On the longer term, microalgae modulate the composition and activity of the photosynthetic apparatus to environmental conditions, an acclimation response activated also in cultures outdoors. While regulation of photosynthesis has been investigated mainly in controlle
Azadi-Chegeni F, Thallmair S, Ward ME, et al., 2022, Protein dynamics and lipid affinity of monomeric, zeaxanthin-binding LHCII in thylakoid membranes, BIOPHYSICAL JOURNAL, Vol: 121, Pages: 396-409, ISSN: 0006-3495
Perin G, Fletcher T, Sagi-Kiss V, et al., 2021, Calm on the surface, dynamic on the inside. Molecular homeostasis of Anabaena sp. PCC 7120 nitrogen metabolism, PLANT CELL AND ENVIRONMENT, Vol: 44, Pages: 1885-1907, ISSN: 0140-7791
Azadi-Chegeni F, Ward ME, Perin G, et al., 2021, Conformational Dynamics of Light-Harvesting Complex II in a Native Membrane Environment., Biophys J, Vol: 120, Pages: 270-283
Photosynthetic light-harvesting complexes (LHCs) of higher plants, moss, and green algae can undergo dynamic conformational transitions, which have been correlated to their ability to adapt to fluctuations in the light environment. Herein, we demonstrate the application of solid-state NMR spectroscopy on native, heterogeneous thylakoid membranes of Chlamydomonas reinhardtii (Cr) and on Cr light-harvesting complex II (LHCII) in thylakoid lipid bilayers to detect LHCII conformational dynamics in its native membrane environment. We show that membrane-reconstituted LHCII contains selective sites that undergo fast, large-amplitude motions, including the phytol tails of two chlorophylls. Protein plasticity is also observed in the N-terminal stromal loop and in protein fragments facing the lumen, involving sites that stabilize the xanthophyll-cycle carotenoid violaxanthin and the two luteins. The results report on the intrinsic flexibility of LHCII pigment-protein complexes in a membrane environment, revealing putative sites for conformational switching. In thylakoid membranes, fast dynamics of protein and pigment sites is significantly reduced, which suggests that in their native organelle membranes, LHCII complexes are locked in specific conformational states.
Perin G, Fletcher T, Sagi-Kiss V, et al., 2020, Calm on the surface, dynamic on the inside. Molecular homeostasis in response to regulatory and metabolic perturbation of<i>Anabaena</i>sp. PCC 7120 nitrogen metabolism
<jats:title>Abstract</jats:title><jats:p>Nitrogen is a key macro-nutrient required for the metabolism and growth of biological systems. Although multiple nitrogen sources can serve this purpose, they are all converted into ammonium/ammonia as a first step of assimilation. It is thus reasonable to expect that molecular parts involved in the transport of ammonium/ammonia across biological membranes (i.e. catalysed by AMT transporters) connect with the regulation of both nitrogen and central carbon metabolism. In order to test this hypothesis, we applied both (1) genetic (i.e. Δ<jats:italic>amt</jats:italic>mutation) and (2) environmental treatments to a target biological system, the cyanobacterium Anabaena sp. PCC 7120. Cyanobacteria have a key role in the global nitrogen cycle and thus represent a useful model system. The aim was to both (1) perturb sensing and low-affinity uptake of ammonium/ammonia and (2) induce multiple inner N states, followed by targeted quantification of key proteins, metabolites and enzyme activities, with experiments intentionally designed over a longer time-scale than the available studies in literature. We observed that the absence of AMT transporters triggered a substantial response at a whole-system level, affecting enzyme activities and the quantity of both proteins and metabolites, spanning both N and C metabolism. Moreover, the absence of AMT transporters left a molecular fingerprint indicating N-deficiency even under N replete conditions (i.e. greater GS activity, lower 2-OG content and faster nitrogenase activation upon N deprivation). Contrasting with all of the above dynamic adaptations was the striking near-complete lack of any externally measurable phenotype (i.e. growth, photosynthesis, pigments, metabolites). We thus conclude that this species evolved a highly robust and adaptable molecular network to maintain homeostasis, resulting in substantial internal but minimal external perturbations.
Perin G, Morosinotto T, 2020, Optimization of Microalgae Photosynthetic Metabolism to Close the Gap with Potential Productivity, Grand Challenges in Algae Biotechnology, Editors: Hallmann, Rampelotto, Publisher: Springer Nature, Pages: 223-248, ISBN: 9783030252335
Microalgae metabolism is powered only by sustainable energy and carbon sources, representing a valuable alternative to develop clean industrial processes. Moreover, this group of unicellular photosynthetic microorganisms shows high versatility, including species from different ecological niches which evolved a variety of pathways to synthesize a wide spectrum of bioactive compounds. However, sophisticated industrial cultivation systems are needed to control the stability of the production process during intensive cultivation. This artificial environment is far different from the ecological niches that shaped these organisms, limiting photon-to-biomass conversion efficiency (PBCE) to values far below those achieved at the lab scale. Moreover, large-scale cultivation has high energetic and operational costs due to initial investment and maintenance, that current PBCE values cannot compensate for, preventing commercial feasibility. Tuning microalgae photosynthetic metabolism represents an unavoidable challenge to improve PBCE and meet the theoretical potential of these organisms.
Bellan A, Bucci F, Perin G, et al., 2020, Photosynthesis regulation in response to fluctuating light in the secondary endosymbiont alga Nannochloropsis gaditana, Plant and Cell Physiology, Vol: 61, Pages: 41-52, ISSN: 0032-0781
In nature, photosynthetic organisms are exposed to highly dynamic environmental conditions where the excitation energy and electron flow in the photosynthetic apparatus need to be continuously modulated. Fluctuations in incident light are particularly challenging since they drive oversaturation of photosynthesis, with consequent oxidative stress and photoinhibition. Plants and algae have evolved several mechanisms to modulate their photosynthetic machinery to cope with light dynamics, such as thermal dissipation of excited chlorophyll states (Non-Photochemical Quenching, NPQ) and regulation of electron transport.The regulatory mechanisms involved in the response to light dynamics have adapted during evolution and exploring biodiversity is a valuable strategy for expanding our understanding of their biological roles. In this work, we investigated the response to fluctuating light in Nannochloropsis gaditana, a eukaryotic microalga of the phylum Heterokonta originating from a secondary endosymbiotic event. N. gaditana is negatively affected by light fluctuations, leading to large reductions in growth and photosynthetic electron transport. Exposure to light fluctuations specifically damages photosystem I, likely because of ineffective regulation of electron transport in this species. The role of Non-Photochemical Quenching, also assessed using a mutant strain specifically depleted of this response, was instead found to be minor, especially in responding to the fastest light fluctuations.
Perin G, Yunus IS, Valton M, et al., 2019, Sunlight-driven recycling to increase nutrient use-efficiency in agriculture, Algal Research, Vol: 41, ISSN: 2211-9264
Humans unsustainably scavenge massive amounts of nutrients from the environment to feed our agricultural systems, thereby perturbing pre-existing natural re-cycling processes. Only a minor fraction of the nutrients are eventually taken up by crops and converted into food, while the majority runs-off into the environment, causing the release of greenhouse gases (e.g. emission of nitrous and nitrogen oxides from the soil) and threatening water security/biodiversity in several ecosystems. The estimated continued growth in global population in the 21st century is expected to place even greater pressure on nutrient use, with likely consequences for the sustainability of human society. Technologies that are able to balance the requirement for intensification of food production with a mitigation of its impact on the environment will be essential to deploy in the near future. The aim is to substantially increase nutrient use-efficiency in order to lower the pressure on finite resources and lighten the environmental impact of intensive agriculture. In this review, we will discuss one such technology, sunlight-driven prokaryotic and eukaryotic microalgae, as a vehicle for both capture and provision of nutrients leached from and provided to agricultural systems, respectively. This technology has the potential to make a difference, but it remains immature and we need to rapidly enhance our knowledge of its opportunities and challenges in order to exploit it for a sustainable circular nutrient economy.
Perin G, Jones PR, 2019, Economic feasibility and long-term sustainability criteria on the path to enable a transition from fossil fuels to biofuels., Current Opinion in Biotechnology, Vol: 57, Pages: 175-182, ISSN: 0958-1669
Currently the production of liquid biofuels relies on plant biomass, which in turn depends on the photosynthetic conversion of light and CO2 into chemical energy. As a consequence, the process is renewable on a far shorter time-scale than its fossil counterpart, thus rendering a potential to reduce the environmental impact of the transportation sector. However, the global economy is not intensively pursuing this route, as current generation biofuel production does not meet two key criteria: (1) economic feasibility and (2) long-term sustainability. Herein, we argue that microalgal systems are valuable alternatives to consider, although it is currently technologically immature and therefore not possible to reach criterion 1, nor evaluate criterion 2. In this review we discuss the major limiting factors for this technology and highlight how further research efforts could be deployed to concretize an industrial reality.
Perin G, Bellan A, Bernardi A, et al., 2019, The potential of quantitative models to improve microalgae photosynthetic efficiency, Physiologia Plantarum, Vol: 166, Pages: 380-391, ISSN: 1399-3054
The massive increase in carbon dioxide concentration in the atmosphere driven by human activities is causing huge negative consequences and new sustainable sources of energy, food and materials are highly needed. Algae are unicellular photosynthetic microorganisms that can provide a highly strategic contribution to this challenge as alternative source of biomass to complement crops cultivation. Algae industrial cultures are commonly limited by light availability, and biomass accumulation is strongly dependent on their photon-to-biomass conversion efficiency. Investigation of algae photosynthetic metabolism is thus strategic for the generation of more efficient strains with higher productivity.
Perin G, Morosinotto T, 2019, Potential of microalgae biomass for the sustainable production of bio-commodities, Progress in Botany, Editors: Lüttge, Publisher: Springer, Berlin, Heidelberg, Pages: 1-34
Human 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.
Formentin E, Sudiro C, Perin G, et al., 2018, Transcriptome and cell physiological analyses in different rice cultivars provide new insights into adaptive and salinity stress responses, Frontiers in Plant Science, Vol: 9, ISSN: 1664-462X
Salinity tolerance has been extensively investigated in recent years due to its agricultural importance. Several features, such as the regulation of ionic transporters and metabolic adjustments, have been identified as salt tolerance hallmarks. Nevertheless, due to the complexity of the trait, the results achieved to date have met with limited success in improving the salt tolerance of rice plants when tested in the field, thus suggesting that a better understanding of the tolerance mechanisms is still required. In this work, differences between two varieties of rice with contrasting salt sensitivities were revealed by the imaging of photosynthetic parameters, ion content analysis and a transcriptomic approach. The transcriptomic analysis conducted on tolerant plants supported the setting up of an adaptive program consisting of sodium distribution preferentially limited to the roots and older leaves, and in the activation of regulatory mechanisms of photosynthesis in the new leaves. As a result, plants resumed grow even under prolonged saline stress. In contrast, in the sensitive variety, RNA-seq analysis revealed a misleading response, ending in senescence and cell death. The physiological response at the cellular level was investigated by measuring the intracellular profile of H2O2 in the roots, using a fluorescent probe. In the roots of tolerant plants, a quick response was observed with an increase in H2O2 production within 5 min after salt treatment. The expression analysis of some of the genes involved in perception, signal transduction and salt stress response confirmed their early induction in the roots of tolerant plants compared to sensitive ones. By inhibiting the synthesis of apoplastic H2O2, a reduction in the expression of these genes was detected. Our results indicate that quick H2O2 signaling in the roots is part of a coordinated response that leads to adaptation instead of senescence in salt-treated rice plants.
Perin G, Bernardi A, Bellan A, et al., 2017, A Mathematical model to guide Genetic Engineering of Photosynthetic Metabolism, Metabolic Engineering, ISSN: 1096-7176
The optimization of algae biomass productivity in industrial cultivation systems requires genetic improvement of wild type strains isolated from nature. One of the main factors affecting algae productivity is their efficiency in converting light into chemical energy and this has been a major target of recent genetic efforts. However, photosynthetic productivity in algae cultures depends on many environmental parameters, making the identification of advantageous genotypes complex and the achievement of concrete improvements slow.In this work, we developed a mathematical model to describe the key factors influencing algae photosynthetic productivity in a photobioreactor, using experimental measurements for the WT strain of Nannochloropsis gaditana. The model was then exploited to predict the effect of potential genetic modifications on algae performances in an industrial context, showing the ability to predict the productivity of mutants with specific photosynthetic phenotypes. These results show that a quantitative model can be exploited to identify the genetic modifications with the highest impact on productivity taking into full account the complex influence of environmental conditions, efficiently guiding engineering efforts.
Perin G, Simionato D, Bellan A, et al., 2017, Cultivation in industrially relevant conditions has a strong influence on biological properties and performances of Nannochloropsis gaditana genetically modified strains, Algal Research, Vol: 28, Pages: 88-99, ISSN: 2211-9264
Microalgae are promising feedstocks for the production of biofuels thanks to their high biomass yield and the lack of competition with food crops for arable land. Algal industrial exploitation, however, still needs to address several technological challenges to reach energetic and economic sustainability. Genetic improvement of microalgae strains is seminal to fully exploit the potential of these organisms.In this work, we investigated how key environmental parameters affected productivity of a promising genetically modified algal strain cultivated in industrially relevant conditions. We observed that intensive growth conditions strongly influenced algae biology as evidenced by molecular and functional analyses. We also showed that specific operational conditions significantly affected performances, enhancing or reducing the advantages of the strains genetic modification, such as the chlorophyll content per cell and the abundance of photosynthetic apparatus components.This work demonstrates the presence of a strong influence of cultivation environment on the phenotype of improved strains, suggesting that operational parameters have a seminal influence on algae performances and must be taken into full account during strains development efforts.
Dolch LJ, Rak C, Perin G, et al., 2017, A Palmitic Acid Elongase Controls Eicosapentaenoic Acid and Plastid MGDG Levels in Nannochloropsis, Plant Physiology, Vol: 173, Pages: 742-759, ISSN: 0032-0889
Nannochloropsis species are oleaginous eukaryotes containing a plastid limited by four membranes, deriving from a secondaryendosymbiosis. In Nannochloropsis, thylakoid lipids, including monogalactosyldiacylglycerol (MGDG), are enriched ineicosapentaenoic acid (EPA). The need for EPA in MGDG is not understood. Fatty acids are de novo synthesized in thestroma, then converted into very-long-chain polyunsaturated fatty acids (FAs) at the endoplasmic reticulum (ER). Theproduction of MGDG relies therefore on an EPA supply from the ER to the plastid, following an unknown process. Weidentified seven elongases and five desaturases possibly involved in EPA production in Nannochloropsis gaditana. Among thesix heterokont-specific saturated FA elongases possibly acting upstream in this pathway, we characterized the highly expressedisoform D0-ELO1. Heterologous expression in yeast (Saccharomyces cerevisiae) showed that NgD0-ELO1 could elongate palmiticacid. Nannochloropsis D0-elo1 mutants exhibited a reduced EPA level and a specific decrease in MGDG. In NgD0-elo1 lines, theimpairment of photosynthesis is consistent with a role of EPA-rich MGDG in nonphotochemical quenching control, possiblyproviding an appropriate MGDG platform for the xanthophyll cycle. Concomitantly with MGDG decrease, the level oftriacylglycerol (TAG) containing medium chain FAs increased. In Nannochloropsis, part of EPA used for MGDG production istherefore biosynthesized by a channeled process initiated at the elongation step of palmitic acid by D0-ELO1, thus acting as acommitting enzyme for galactolipid production. Based on the MGDG/TAG balance controlled by D0-ELO1, this study alsoprovides novel prospects for the engineering of oleaginous microalgae for biotechnological applications.
Azadi Chegeni F, Perin G, Sai Sankar Gupta KB, et al., 2016, Protein and lipid dynamics in photosynthetic thylakoid membranes investigated by in-situ solid-state NMR, Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol: 1857, Pages: 1849-1859, ISSN: 0005-2728
Perin G, Cimetta E, Monetti F, et al., 2016, Novel micro-photobioreactor design and monitoring method for assessing microalgae response to light intensity, Algal Research, Vol: 19, Pages: 69-76, ISSN: 2211-9264
Alboresi A, Perin G, Vitulo N, et al., 2016, Light Remodels Lipid Biosynthesis in Nannochloropsis gaditana by Modulating Carbon Partitioning Between Organelles, Plant Physiology, Pages: pp.00599.2016-pp.00599.2016, ISSN: 0032-0889
Perin G, Bellan A, Segalla A, et al., 2015, Generation of random mutants to improve light-use efficiency of Nannochloropsis gaditana cultures for biofuel production, Biotechnology for Biofuels, Vol: 8, ISSN: 1754-6834
BackgroundThe productivity of an algal culture depends on how efficiently it converts sunlight into biomass and lipids. Wild-type algae in their natural environment evolved to compete for light energy and maximize individual cell growth; however, in a photobioreactor, global productivity should be maximized. Improving light use efficiency is one of the primary aims of algae biotechnological research, and genetic engineering can play a major role in attaining this goal.ResultsIn this work, we generated a collection of Nannochloropsis gaditana mutant strains and screened them for alterations in the photosynthetic apparatus. The selected mutant strains exhibited diverse phenotypes, some of which are potentially beneficial under the specific artificial conditions of a photobioreactor. Particular attention was given to strains showing reduced cellular pigment contents, and further characterization revealed that some of the selected strains exhibited improved photosynthetic activity; in at least one case, this trait corresponded to improved biomass productivity in lab-scale cultures.ConclusionsThis work demonstrates that genetic modification of N. gaditana has the potential to generate strains with improved biomass productivity when cultivated under the artificial conditions of a photobioreactor.
Perin G, Segalla A, Basso S, et al., 2014, Biotechnological Optimization of Light Use Efficiency in Nannochloropsis Cultures for Biodiesel Production, Chemical Engineering Transactions, ISSN: 1974-9791
Bernardi A, Perin G, Sforza E, et al., 2014, An identifiable state model to describe light intensity influence on microalgae growth, Industrial && Engineering Chemistry Research, Vol: 53, Pages: 6738-6749, ISSN: 0888-5885
Despite the high potential as feedstock for the production of fuels and chemicals, the industrial cultivation of microalgae still exhibits many issues. Yield in microalgae cultivation systems is limited by the solar energy that can be harvested. The availability of reliable models representing key phenomena affecting algae growth may help designing and optimizing effective production systems at an industrial level. In this work the complex influence of different light regimes on seawater alga Nannochloropsis salina growth is represented by first principles models. Experimental data such as in vivo fluorescence measurements are employed to develop the model. The proposed model allows description of all growth curves and fluorescence data in a reliable way. The model structure is assessed and modified in order to guarantee the model identifiability and the estimation of its parametric set in a robust and reliable way.
Bernardi A, Perin G, Galvanin F, et al., 2013, Modeling the Effect of Light Intensity in Microalgae Growth, Publisher: 2013 AIChE Annual Meeting
Bernardi A, Perin G, Galvanin F, et al., 2013, Modeling the effect of light intensity in microalgae growth, Pages: 349-350
Perin G, Bellan A, Lyska D, et al., Modulation of xanthophyll cycle impacts biomass productivity in the marine microalga <i>Nannochloropsis</i>
<jats:title>Abstract</jats:title><jats:p>Life on earth depends on photosynthetic primary producers that exploit sunlight to fix CO<jats:sub>2</jats:sub> into biomass. Approximately half of global primary production is associated with microalgae living in aquatic environments. Microalgae also represent a promising source of biomass to complement crop cultivation, and they could contribute to the development of a more sustainable bioeconomy. Photosynthetic organisms evolved multiple mechanisms involved in the regulation of photosynthesis to respond to highly variable environmental conditions. While essential to avoid photodamage, regulation of photosynthesis results in dissipation of absorbed light energy, generating a complex trade-off between protection from stress and light-use efficiency. This work investigates the impact of the xanthophyll cycle, the light-induced reversible conversion of violaxanthin into zeaxanthin, on the protection from excess light and on biomass productivity in the marine microalgae of the genus <jats:italic>Nannochloropsis</jats:italic>. Zeaxanthin is shown to have an essential role in protection from excess light, contributing to the induction of Non-Photochemical Quenching and scavenging of reactive oxygen species. On the other hand, the overexpression of Zeaxanthin Epoxidase, enables a faster re-conversion of zeaxanthin to violaxanthin that is shown to be advantageous for biomass productivity in dense cultures in photobioreactors. These results demonstrate that zeaxanthin accumulation is critical to respond to strong illumination, but it may lead to unnecessary energy losses in light-limiting conditions, and accelerating its re-conversion to violaxanthin provides an advantage for biomass productivity in microalgae.</jats:p><jats:sec><jats:title>Significance Statement</jats:title><jats:p>This work investigates the impact of the xanthophyll cycle in marine microalgae
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