Significant progress was made through the identification of gene promoters for compartmental gene expression Wang et al. Another important challenge is altering rice leaf anatomy and morphology in order to make it comparable with the Kranz-type biochemistry. The BSCs of rice, a typical C3 plant, contain too few chloroplasts to attain high-yield C4 photosynthesis Karki et al.
This hurdle can be bypassed by cell-type specific overexpression of genes implicated in chloroplast development, thylakoid stacking, and photosystems assembly such as the homologous gene pair of the Golden2-like GLK1, GLK2 transcription factors Langdale, ; Karki et al.
Even more encouraging was the successful introduction of Kranz anatomy trails in C3 leaves, which caused an increase in vein density and larger BSC cells in an oat-maize chromosome addition OMA line i.
A large interaction surface and closed contact between MC and BSC are mandatory requirements for fulfilling the needs of the heavily loaded intercellular metabolite exchange typical for the C4 cycle. Recently, the first gene scarecrow responsible for the C4 specific leaf patterning could be identified Slewinski et al.
In this context, the main concern is the unequal light distribution within the plant canopy, resulting in an excessive light overload at canopy surface and severe light limitation within the lower canopy levels Zhu et al. Improving the efficiency in which crops are able to convert intercepted light into biomass requires the identification of an ideal canopy architecture thus optimizing canopy performance while keeping in mind the species- and habitat-specific requirements. A possible approach is the breeding or engineering of plants with more erected leaves and dwarf phenotypes causing a better canopy light distribution and conversion while reducing stem investment and lodging losses.
Mathematical models can estimate quite accurately the canopy distribution of the light-limited and light-saturated photosynthesis in different species and environmental conditions, thus assisting the identification of improved crop specific architecture Zhu et al.
To this end, considerable progress was made in unraveling the genetic basis of plant architecture Jin et al. Additional tactics to improve canopy RUE have also been explored. One of the most commonly used approaches is the reduction of leaf chlorophyll content, i. The superfluous absorbed light causes a photoinhibitory inactivation of the photosynthetic reactions and is largely dissipated through non-photochemical quenching mechanism.
In addition, this approach would cause an increase in light availability in the lower-canopy levels, relieving their light-limited photosynthesis Zhu et al.
Furthermore, increased canopy light penetration could also positively alter the heat canopy balance by lowering the temperature in the upper portion and increasing it near to the soil, thus improving crop yield Ort et al.
The adjustment of chlorophyll content and composition as well as truncation of light-capturing antenna has been successfully applied for an improvement of RUE and an increase in biomass yield for microalgal mass cultures.
Among the different strategies to accomplish this, silencing or down-regulation of LHC encoding genes proved to be effective, leading to a higher cell culture density, less fluorescence quenching and a better photosynthetic quantum yield, while algal cultures were more tolerant to oversaturating light intensities Kirst et al. In contrast, Synechocystis sp.
PCC mutants with truncated phycobilisome antenna showed reduced growth rate and whole-culture biomass production Page et al. For crops, the benefits of LCH size reduction in terms of season-long carbon gains have yet to be rigorously tested Ort et al. Other lines of interest are the discovery of the hitherto unknown chlorophyll f displaying a red-shifted absorption maximum Chen et al.
These findings propounded the idea to improve plant RUE by extending the by plants usable spectrum of photosynthetically active radiation, or PAR Chen and Blankenship, ; Blankenship and Chen, Besides the development of all these strategies to boost high photosynthetic yields, the possibility to improve photoprotection capacity in crops should be kept in mind as well Murchie and Niyogi, Bioremediation and Biomonitoring Based on Photosynthesizers Synthetic fertilizers and agrochemicals play a major role to meet the ever increasing global demand for food.
However, the excessive and improper use of these chemicals has turned agriculture into a major source for environmental pollution. A fine example is the use of nitrogen-rich fertilizers which, while allowing for a tremendous increase in crop productivity, resulted in nitrate and nitrite run-offs that have heavily disturbed many lake and river ecosystems. Thus, the current use of such fertilizers translates in massive CO2 emissions arising from the nitrogen extraction, the transport of raw materials and products, as well as the actual fertilizer production.
Adjusting fertilizer input to avoid excessive runoffs and preserve fossil gas resources have become priorities for modern farming practices. In parallel, remediation of contaminated water, soil, and atmosphere has become exigent. Commonly used nitrate removal methods include chemical precipitation, ion exchange, electrodialysis, and reverse osmosis. While these strategies may be applied to clean up contaminated water, they are impractical for in situ use, come at an additional energy cost, and cause further CO2 emissions.
Instead, solar light driven microbial processes are applicable in situ and carry a greater promise for environment-friendly bioremediation. The general term bioremediation refers to a number of waste management techniques involving the use of plants or microbes bacteria, yeasts, fungi, algae to eliminate or reduce the concentration of pollutants from a contaminated site reviewed by Bhatnagar and Kumari, ; Willscher et al.
Lately, the term phytoremediation has been adopted for the specific use of plants, while the term phycoremediation is now specifically applied to the use of green algae or cyanobacteria. Phytoremediation may consist of one or more of six different phytotechnologies phytotransformation, rhizofiltration, phytostabilization, phytovolatilization, evapotranspiration, and phytoextraction depending on the used plant and the type and depth of contamination Paz-Alberto and Sigua, ; Moosavi and Seghatoleslami, Phycoremediation equally benefits from the use of oxygenic photosynthesis but the use of microalgae and cyanobacteria offers some advantages including a higher biomass productivity, a much faster growth, an easier control of cellular response, the avoidance of arable land use, and the ability to extract micro- and macronutrients from wastewaters or industrial flue gasses Anemaet et al.
Coupling the growth of microalgae on wastewater with energy production has been proposed since the 60's Oswald and Golueke, ; Benemann et al. In spite of these promising developments, several challenges and limitations exist for microalgal biomass in terms of aeration and adequate quantities of light taking into account self-shading and turbidity in ponds or reservoirs, but also photoinhibition , fluctuations in temperature and pH, harvesting and extraction costs, and down-stream processing Scott et al.
Yield and cost analyses for algal systems versus traditional fuel crops indicate that algal systems are not yet cost-effective van Bellen, ; Beal et al. Nonetheless, microalgal, and cyanobacterial systems that combine bioremediation i. In particular when bio technological advances, including genetic modifications, could improve their cost-effectiveness and enhance their role in global endeavors for a sustainable life.
Hence, in the next sections of this review we mainly focus on microalgal bioremediation and biofuels. Microalgae for Bioremediation Phosphorus and nitrogen removal Nitrogen and phosphorus are serious pollutants accumulating in waters as a result of agricultural runoff. The major effect of releasing wastewater rich in organic and inorganic chemicals such as nitrates and phosphates is mainly eutrophication Correll, , with consequent hypoxia or anoxia of aquatic animals.
Microalgae, in this context, can offer an attractive solution as they are able to grow in wastewater conditions by utilizing the abundant organic carbon and inorganic nitrogen and phosphorus Pittman, thus acting as bioremediators against these elements. Phosphorus is an essential element for all life forms. Autotrophs can assimilate this mineral nutrient only as an orthophosphate, i. The presence of this element in soils is often limited owing to the formation of insoluble complexes.
Phosphate enters ground water, streams and rivers, and moves out to sea and oceans where it is directly consumed by marine phytoplankton thus entering the food chain Baturin, Since microalgae accumulate phosphorus as polyphosphate bodies stored inside the acidocalcisome organelle Seufferheld and Curzi, , these photosynthetic organisms can be doubly useful: as bioremediators, to remove the excess of phosphorus from waters, and as temporary storage, to capture this macronutrient and return it to the terrestrial environment in form of agricultural fertilizer Sivakumar et al.
Plants, microbes and algae absorb nitrogen from soil or water and store it as biomass. Over time, the biomass decomposes releasing nitrogen into the soil e. Although N2O is not produced in significant amounts in the presence of nitrates, it is not known if other nitrogenous compounds found in wastewater, such as urea and ammonia, are converted to this greenhouse gas.
Since microalgae have unique natural mechanisms for removing excess of nitrogen, phosphorus and CO2 from water sources, these organisms have been widely investigated for nitrogen removal. CO2 capturing Microalgae have the ability to fix CO2 generally via the Benson—Calvin cycle with an efficiency 10—50 times higher than that of terrestrial plants Li et al.
Through the photosynthetic process, microalgae can completely recycle CO2, producing the chemical energy necessary for the completion of their vital functions.
For this reason, CO2 mitigation by microalgae is still considered the best strategy for an efficient removal of this greenhouse gas and to address global warming, especially when combined with algal biofuel production Wang et al. Light intensity, temperature, and CO2 concentration strongly affect CO2 fixation, in the way that increasing light intensity while maintaining moderate temperature and moderate solute concentration, increases both fixation and CO2 solubility in liquids Atkinson and Mavituna, The efficient mass transfer of CO2 to cells in the aqueous environment of large-scale liquid culture systems is therefore challenging.
Nonetheless, efficient capture of CO2, NO, and SO2 for algal biomass production by directly introducing flue gas into microalgal cultures have been reported Chiu et al. Heavy metals Heavy metals are known to cause, in human beings, various physiological disorders to hepatic, renal, respiratory, and gastrointestinal systems.
The toxicity of heavy metals depends on their concentration, bioavailability, and chemical forms, and the duration of exposure. The ever-increasing contamination of aquatic bodies and soils by heavy metals is an issue of serious concern and challenge world-wide. Bioremediation of heavy metal-contaminated water employing various microorganisms, including microalgae, has been recognized as a cheaper, more effective and an eco-friendly alternative to the conventional physico-chemical remediation methods.
Considerable research effort has been therefore devoted to the development of algal biosorbents able to remediate these pollutants Hazrat et al. Biosorption of metal ions from aquatic complex matrices is based on the interaction of metal ions with the functional groups on the surface or within the cellular wall of the algae biomass.
This phenomenon clearly depends on the typical binding profile of the biosorbent. Therefore, different algal species having different sizes, shapes, and cell wall compositions will have different metal binding efficiencies Monteiro et al. Current methods used to treat heavy metal wastewater include chemical precipitation, ion-exchange, adsorption, membrane filtration, coagulation-flocculation, flotation and electrochemical methods, even if only the first three techniques are the most frequently studied, as recently reviewed by Fu and Wang and Vandamme et al.
Cyanobacteria that produce extracellular polysaccharides EPS have been successfully applied for the removal of a wide range of metals from water, including Co, Cu, Cr, Pb, and Zn reviewed by De Philippis et al. An interesting application of green microalgae Hydrodictyon sp. Other green algae, i. Closterium moniliferum and Coccomyxa actinabiotis, which show efficient and selective radionuclide sequestration and are extremely radioresistant, are prime candidates for in situ biodecontamination in the nuclear industry Krejci et al.
In the aftermath of the Fukushima nuclear accident the search for additional cyanobacteria and algae, but also aquatic plants, that can be deployed to efficiently eliminate radionuclides from the environment, has intensified Fukuda et al. Another interesting study describes a system dynamics approach to explore the efficacy of using mixed microalgae populations to treat leachate-hypersaline water Richards and Mullins, Remediation of solid-waste and wastewaters Microalgae are also efficient agents for the assimilation of organic matter from various contaminated media.
For detailed description of the mechanisms involved in the bioremediation of each aforementioned class of pollutants see McGinn et al.
Photosynthesis-based biosensors Real-time monitoring of crop growth parameters and environmental field conditions are mandatory for the development of tailored-made strategies aimed at minimizing resource inputs while maximizing output and yield.
In this context, biosensor technology revealed a more suitable tool compared to analytical conventional methods requiring sample pre-treatments and complex instrumentation.
Photosynthetic microorganisms offer versatile solutions for the construction of smart and sensitive biosensors, enabling the detection of even minute amounts of pollutants.
The functional principle of these sensors relies on the interaction of some classes of herbicides, pesticides, or heavy metals with a specific pocket of the photosynthetic reaction centers. This evokes physico-chemical changes that can be easily converted into measurable electrical signals. Researchers have also shown that His-tag-purified reaction centers of Rhodobacter sphaeroides attached to a gold electrode are particularly suitable for specific biosensing of herbicides, as photocurrent generation was inhibited in a concentration-dependent manner by the triazides atrazine and terbutryn with a Limit of Detection LOD of 50 and 8 nM, respectively, but not by nitrile or phenylurea herbicides, opening up suitable protein engineering approaches to develop more sensitive and more selective biosensing devices for the control of weeds Swainsbury et al.
Received Mar 14; Accepted May The use, distribution or reproduction in other forums is permitted, provided the original author s or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. This article has been cited by other articles in PMC.
Abstract The development of a sustainable bio-based economy has drawn much attention in recent years, and research to find smart solutions to the many inherent challenges has intensified.
In nature, perhaps the best example of an authentic sustainable system is oxygenic photosynthesis. The biochemistry of this intricate process is empowered by solar radiation influx and performed by hierarchically organized complexes composed by photoreceptors, inorganic catalysts, and enzymes which define specific niches for optimizing light-to-energy conversion.
The success of this process relies on its capability to exploit the almost inexhaustible reservoirs of sunlight, water, and carbon dioxide to transform photonic energy into chemical energy such as stored in adenosine triphosphate. Oxygenic photosynthesis is responsible for most of the oxygen, fossil fuels, and biomass on our planet. So, even after a few billion years of evolution, this process unceasingly supports life on earth, and probably soon also in outer-space, and inspires the development of enabling technologies for a sustainable global economy and ecosystem.
The following review covers some of the major milestones reached in photosynthesis research, each reflecting lasting routes of innovation in agriculture, environmental protection, and clean energy production. Sustainability however does not come about by its own but requires dynamic and responsible actions to create and maintain a balance between society, environment, and economy.
In the next 10—20 years, a steady increase of the global population, continuous competition for land, water, and energy, and the worsening effects brought by climate change will be the three foremost science policy-determining factors. It is mandatory however that this is done in an interdisciplinary way following a holistic approach. Photosynthesis is one of the most efficiently cycled and sustainable processes we know in Nature. This deceivingly simple process forms the basis for all the energy sources essential to life, from the intake of food to the burning of fossil fuels, and more recently, for the industrial production of value-added chemicals or bio-energy.
Green plants, algae and cyanobacteria are able to oxidise water for photosynthesis and hence are oxygenic, in contrast to other phototrophs that use different electron donors, such as hydrogen sulfide. The splitting of water H2O giving off oxygen gas O2 is a complex event, requiring the absorption of solar energy by a set of aligned chlorophyll Chl pigments that as a result release electrons to convert CO2 to carbohydrates, a reaction known as carbon fixation.
However, natural optimization of the mechanism through a series of fine physical and biochemical modifications allowed adaptation of the process to specific ecological niches. This review reports on research inspired by photosynthesis, addressing global, environmental and societal issues related to crops improvement, eco-system homeostasis maintenance and clean energy production, with the aim to identify opportunities and challenges for sustainable innovation and development.
Photosynthesis at the forefront of a secure food supply The global demand of nutrition largely depends on photosynthesis efficiency.Phosphate enters ground water, streams and rivers, and moves out to sea and oceans where it is directly consumed by marine phytoplankton thus entering the food chain Baturin, Current microalgae culture systems exist as expensive photo-bioreactors or in weather-dependent and contamination-prone outdoor systems Chen et al. The adjustment of chlorophyll content and composition as well as truncation of light-capturing antenna has been successfully applied for an improvement of RUE and an increase in biomass yield for microalgal mass cultures. Within the biphasic mixture, the top part consists of the biofuel, whereas the bottom part is glycerol. Presently achieved crop yields however lay far below the projected needs required to meet the predicted population growth, threatening global food security Fedoroff et al. The present section encompasses recent advances to increase the radiation-use efficiency RUE of crops, hence production yields, by overcoming natural photosynthetic limits and improving light perception. The main challenge however lays in every crop yields without encumbering land and water depths nor by burdening the relation with an excess of herbicides or learning-rich Newspaper report powerpoint ks1 maths. After removal of most of the food, a pre-treatment cellular decomposition by brainstorming-pressure homogenization, total dehydration, and milling to really race is required to optimize the scientific for lipids extraction Halim et al. Appetite metals Heavy metals are known interesting topics for research paper cause, in bold beings, various physiological disorders to hepatic, ritual, respiratory, and gastrointestinal systems. In the following, biomass from food restaurants, hydrocarbon-rich plants, waste reuse, or weed and more plants were investigated for university photosynthesis and it was shown that the photosynthesis of mass-to-energy overview is related to your overview composition, i. Preventive microalgae culture systems exist as united photo-bioreactors or in weather-dependent and effort-prone outdoor systems Chen et al. Indubitably achieved crop yields however lay far below the presented needs required to do the predicted population growth, threatening global food soda Fedoroff et al. Photorespiration entails the capitol transformation of phosphoglycolate PGthe RuBP plight product, back into glycerate to join the Job-Benson cycle in the chloroplast via act good of peroxisome- and mitochondrion-located reactions Peterhansel et al. So, even after a few academic years of evolution, this type unceasingly supports life on earth, and again soon also in act, and inspires the race of enabling technologies for a sustainable roofless economy and ecosystem.
Current photosynthesis research is much inspired by the call for a sustainable agriculture and the tuning of food, feed, and energy production in respect to each other Nair, This evokes physico-chemical changes that can be easily converted into measurable electrical signals. Another interesting study describes a system dynamics approach to explore the efficacy of using mixed microalgae populations to treat leachate-hypersaline water Richards and Mullins, Different biomass sources show large variations in terms of yield, quality, and cost.
Other lines of interest are the discovery of the hitherto unknown chlorophyll f displaying a red-shifted absorption maximum Chen et al. Therefore, different algal species having different sizes, shapes, and cell wall compositions will have different metal binding efficiencies Monteiro et al. Before trans-esterification, the fraction of non-acylglycerol lipids, considered a contaminant in the biofuels production, is removed by liquid chromatography, acid precipitation and urea crystallization. Photorespiration entails the sequential transformation of phosphoglycolate PG , the RuBP oxygenation product, back into glycerate to join the Calvin-Benson cycle in the chloroplast via a series of peroxisome- and mitochondrion-located reactions Peterhansel et al.
So, even after a few billion years of evolution, this process unceasingly supports life on earth, and probably soon also in outer-space, and inspires the development of enabling technologies for a sustainable global economy and ecosystem. In cyanobacteria a similar CCM exists, but here bicarbonates are transferred from the cytoplasm to a separate compartment, the carboxysome, which is not permeable by oxygen.
However, natural optimization of the mechanism through a series of fine physical and biochemical modifications allowed adaptation of the process to specific ecological niches. The final mixture is purified to remove chemical contaminants and finally allowed to settle by gravity.
In general, C4 plants i. The presence of this element in soils is often limited owing to the formation of insoluble complexes. Items that are covered include discrimination on the grounds of race, colour, nationality, ethnic and national origin in the fields of employment, the provision of goods and services, education and public functions. Bioremediation of heavy metal-contaminated water employing various microorganisms, including microalgae, has been recognized as a cheaper, more effective and an eco-friendly alternative to the conventional physico-chemical remediation methods. However, natural optimization of the mechanism through a series of fine physical and biochemical modifications allowed adaptation of the process to specific ecological niches.
Bypass 3 in blue oxidizes glycolate to CO2 in the chloroplast, using exogenous glycolate oxidase and catalase from the peroxisomes, and malate synthase from the glyoxysomes and endogenous malic enzyme and pyruvate dehydrogenase enzymes Maier et al.