Solar water splitting Pt-nanoparticle photosystem I thylakoid systems: Catalyst identification,location and oligomeric structure

Photosynthetic conversion of light energy into chemical energy occurs in sheet-like membrane-bound compartments called thylakoids and is mediated by large integral membrane protein-pigment complexes called reaction centers (RCs). Oxygenic photosynthesis of higher plants, cyanobacteria and algae requires the symbiotic linking of two RCs, photosystem II (PSII) and photosystem I (PSI), to split water and assimilate carbon dioxide. Worldwide there is a large research investment in developing RC-based hybrids that utilize the highly evolved solar energy conversion capabilities of RCs to power catalytic reactions for solar fuel generation. Of particular interest is the solar-powered production of H₂, a clean and renewable energy source that can replace carbon-based fossil fuels and help provide for ever-increasing global energy demands. Recently, we developed thylakoid membrane hybrids with abiotic catalysts and demonstrated that photosynthetic Z-scheme electron flow from the light-driven water oxidation at PSII can drive H₂ production from PSI. One of these hybrid systems was created by self-assembling Pt-nanoparticles (PtNPs) with the stromal subunits of PSI that extend beyond the membrane plane in both spinach and cyanobacterial thylakoids. Using PtNPs as site-specific probe molecules, we report the electron microscopic (EM) imaging of oligomeric structure, location and organization of PSI in thylakoid membranes and provide the first direct visualization of photosynthetic Z-scheme solar water-splitting biohybrids for clean H₂ production.     

Biohydrogen production from microalgae—Major bottlenecks and future research perspectives

The imprudent use of fossil fuels has resulted in high greenhouse gas (GHG) emissions, leading to climate change and global warming. Reduction in GHG emissions and energy insecurity imposed by the depleting fossil fuel reserves led to the search for alternative sustainable fuels. Hydrogen is a potential alternative energy carrier and is of particular interest because hydrogen combustion releases only water. Hydrogen is also an important industrial feedstock. As an alternative energy carrier, hydrogen can be used in fuel cells for power generation. Current hydrogen production mainly relies on fossil fuels and is usually energy and CO₂-emission intensive, thus the use of fossil fuel-derived hydrogen as a carbon-free fuel source is fallacious. Biohydrogen production can be achieved via microbial methods, and the use of microalgae for hydrogen production is outstanding due to the carbon mitigating effects and the utilization of solar energy as an energy source by microalgae. This review provides comprehensive information on the mechanisms of hydrogen production by microalgae and the enzymes involved. The major challenges in the commercialization of microalgae-based photobiological hydrogen production are critically analyzed and future research perspectives are discussed. Life cycle analysis and economic assessment of hydrogen production by microalgae are also presented.     

Challenges and opportunities for photochemists on the verge of solar energy conversion.

Has photochemistry missed the boat on solar energy conversion? Certainly not, but it is time to reach out and make a difference if we do not want to have to choose between feeding our families or our thirst for fuel. Compared to other initiatives, such as biofuels or nuclear fusion, direct conversion of solar energy into electricity or fuels is lagging behind in terms of funding, and this is slowing progress on overcoming critical bottlenecks. This perspective outlines some of the key fundamental issues in solar energy conversion based on organic photovoltaic devices or artificial photosynthesis where being a photochemist can make a difference.     

Evolution of reaction center mimics to systems capable of generating solar fuel

Capturing and converting solar energy via artificial photosynthesis offers an ideal way to limit society’s dependence on fossil fuel and its myriad consequences. The development and study of molecular artificial photosynthetic reactions centers and antenna complexes and the combination of these constructs with catalysts to drive the photochemical production of a fuel helps to build the understanding needed for development of future scalable technologies. This review focuses on the study of molecular complexes, design of which is inspired by the components of natural photosynthesis, and covers research from early triad reaction centers developed by the group of Gust, Moore, and Moore to recent photoelectrochemical systems capable of using light to convert water to oxygen and hydrogen.     

Effect of solar ultraviolet-B radiation during springtime ozone depletion on photosynthesis and biomass production of Antarctic vascular plants

We assessed the influence of springtime solar UV-B radiation that was naturally enhanced during several days due to ozone depletion on biomass production and photosynthesis of vascular plants along the Antarctic Peninsula. Naturally growing plants of Colobanthus quitensis (Kunth) Bartl. and Deschampsia antarctica Desv. were potted and grown under filters that absorbed or transmitted most solar UV-B. Plants exposed to solar UV-B from mid-October to early January produced 11% to 22% less total, as well as above ground biomass, and 24% to 31% less total leaf area. These growth reductions did not appear to be associated with reductions in photosynthesis per se: Although rates of photosynthetic O(2) evolution were reduced on a chlorophyll and a dry-mass basis, on a leaf area basis they were not affected by UV-B exposure. Leaves on plants exposed to UV-B were denser, probably thicker, and had higher concentrations of photosynthetic and UV-B absorbing pigments. We suspect that the development of thicker leaves containing more photosynthetic and screening pigments allowed these plants to maintain their photosynthetic rates per unit leaf area. Exposure to UV-B led to reductions in quantum yield of photosystem II, based on fluorescence measurements of adaxial leaf surfaces, and we suspect that UV-B impaired photosynthesis in the upper mesophyll of leaves. Because the ratio of variable to maximal fluorescence, as well as the initial slope of the photosynthetic light response, were unaffected by UV-B exposure, we suggest that impairments in photosynthesis in the upper mesophyll were associated with light-independent enzymatic, rather than photosystem II, limitations.     

Genetic structure of a novel biofuel-producing microorganism community

Biofuels are an important alternative, renewable source of energy in the face of the ongoing depletion of fossil fuels. Cheese whey is a dairy industry waste characterized by high lactose concentration, which represents a significant environmental problem. Bio-ethanol production by cheese whey could be an effective nonvegetable source for renewable energy production. Here, we report the isolation of a mixed microbial population, able to produce ethanol as main fermentation product from fermenting whey. The microbial consortium has been used to perform a batch fermentation of crude whey in both anoxic and hypoxic conditions. Maximum ethanol concentrations achieved in this study was obtained using the mixed culture in hypoxic conditions, grown at pH 4 and 30°C, with ethanol production yield of 60 g/L. Our research has pointed out an alternative way to both dispose and valorize cheese whey, a dairy by-product that could cause water pollution and harm to the environment if not properly treated.     

Sources of variability in greenhouse gas and energy balances for biofuel production: a systematic review

Across the energy sector, alternatives to fossil fuels are being developed, in response to the dual drivers of climate change and energy security. For transport, biofuels have the greatest potential to replace fossil fuels in the short‐to medium term. However, the ecological benefits of biofuels and the role that their deployment can play in mitigating climate change are being called into question. Life Cycle Assessment (LCA) is a widely used approach that enables the energy and greenhouse gas (GHG) balance of biofuel production to be calculated. Concerns have nevertheless been raised that published data show widely varying and sometimes contradictory results. This review describes a systematic review of GHG emissions and energy balance data from 44 LCA studies of first‐ and second‐generation biofuels. The information collated was used to identify the dominant sources of GHG emissions and energy requirements in biofuel production and the key sources of variability in published LCA data. Our analysis revealed three distinct sources of variation: (1) ‘real’ variability in parameters e.g. cultivation; (2) ‘methodological’ variability due to the implementation of the LCA method; and (3) ‘uncertainty’ due to parameters rarely included and poorly quantified. There is global interest in developing a sustainability assessment protocol for biofuels. Confidence in the results of such an assessment can only be assured if these areas of uncertainty and variability are addressed. A more defined methodology is necessary in order to allow effective and accurate comparison of results. It is also essential that areas of uncertainty such as impacts on soil carbon stocks and fluxes are included in LCA assessments, and that further research is conducted to enable a robust calculation of impacts under different land‐use change scenarios. Without the inclusion of these parameters, we cannot be certain that biofuels are really delivering GHG savings compared with fossil fuels.     

光系统Ⅱ的结构与功能以及光合膜对环境因素的响应机制

光合膜是地球上捕获、转换和利用太阳能的关键场所,光合膜的活动所提供的能源、粮食及氧气,是人类世界赖以生存的基础。经过35亿年的进化,光合膜已经进化成了一个高度精密的结构,色素分子高密度结合并合理排列,具有高精度的能级耦联网络和高效率的能量传递系统,这使得光合膜成为自然界中能够最高效地吸收和传递太阳能、并能在常温常压下高效地将太阳能转换成化学能和还原势的色素蛋白复合体体系。由于这一特性,光合膜被认为是最有潜力的固定太阳能的新材料,并为研究新型光电转换器件提供了新思路和新理论。因此,长期以来,光合膜的结构-功能关系研究及其功能模拟,特别是执行固定和转化太阳能第一步的光系统Ⅱ,在新能源的利用中吸引了大量的研究力量,取得了突飞猛进的进展。本文总结了近年来关于光系统Ⅱ的结构与功能,以及光合膜对环境的感应和功能调节机制等方面的研究进展。     

Algal Photosynthesis as the Primary Driver for a Sustainable Development in Energy, Feed, and Food Production

High oil prices and global warming that accompany the use of fossil fuels are an incentive to find alternative forms of energy supply. Photosynthetic biofuel production represents one of these since for this, one uses renewable resources. Sunlight is used for the conversion of water and CO₂ into biomass. Two strategies are used in parallel: plant-based production via sugar fermentation into ethanol and biodiesel production through transesterification. Both, however, exacerbate other problems, including regional nutrient balancing and the world's food supply, and suffer from the modest efficiency of photosynthesis. Maximizing the efficiency of natural and engineered photosynthesis is therefore of utmost importance. Algal photosynthesis is the system of choice for this particularly for energy applications. Complete conversion of CO₂ into biomass is not necessary for this. Innovative methods of synthetic biology allow one to combine photosynthetic and fermentative metabolism via the so-called Photanol approach to form biofuel directly from Calvin cycle intermediates through use of the naturally transformable cyanobacterium Synechocystis sp. PCC 6803. Beyond providing transport energy and chemical feedstocks, photosynthesis will continue to be used for food and feed applications. Also for this application, arguments of efficiency will become more and more important as the size of the world population continues to increase. Photosynthetic cells can be used for food applications in various innovative forms, e.g., as a substitute for the fish proteins in the diet supplied to carnivorous fish or perhaps—after acid hydrolysis—as a complex, animal-free serum for growth of mammalian cells in vitro.     

产生物柴油微藻培养研究进展

石油的大量使用会导致能源枯竭和温室气体（CO2）排放的增加。为了实现经济和环境的和谐发展,必须使用可再生能源代替石油。可再生能源使用后不会造成温室气体排放的增加。生物柴油是一种理想的可再生能源, 能满足以上要求,所以近年来得到迅速发展。微藻是一种主要利用太阳能固定 CO2,生成制备生物柴油所需油脂的藻类。因此以微藻油脂为原料转化成的生物柴油是石油理想的替代品。简要介绍了产油微藻的种类和微藻油脂的合成,较详细地阐述了微藻自养培养、异养培养、生物反应器、工程微藻的最新研究进展,并初步展望了微藻产油研究的未来发展方向。     

Process development and evaluation for algal glycerol production

This article and develops a process for large-scale production of glycerol by means of a hemophilic algae. The process is shown to be economically and technically feasible. Although the proposed process is extremely capital intensive, the total production cost is competitive with existing glycerol process. In addition, the overall energy requirement is much lower than that of the petrochemical process. This proposed process provides an alternative route for glycerol production that is minimally dependent on fossil fuels and is therefore, less sensitive to crude oil availability and price. The primary raw material carbon dioxide from stack gas, is an inexpensive and renewable resource. Maximal Utilization of solar energy is made not only in the glycerol synthesis steps but also in the product recovery system. Significant improvement in the process economics can be realized through further development of large-scale cultivation technology, and biomass distribution and collection machinery. Due to the labor intensive nature of the proposed algal process, it is particularly suitable for less developed nations with limited fossil fuel resources and lower labor costs.     

Comparative life cycle assessment of uses of rice husk for energy purposes

Purpose  

Recently, the Thai government has been advancing the expanded use of biomass as an alternative source of energy substituting it for the fossil fuels that have been shown to be harmful to the environment. Rice husk, one of the main sources of biomass in Thailand, has already been used as an energy source in many different applications and has been successful in reducing the consumption of fossil fuels. At present (2011), the main use of rice husk in Thailand is as fuel to generate electricity. However, rice husk can potentially be used to produce other forms of energy such as cellulosic ethanol. This paper compares the environmental performance of the current main use of rice husk for energy purposes in the Thai context, i.e., for electricity generation with the prospective use, i.e., for cellulosic ethanol production. The results from this study will identify the more environmentally friendly option for use of rice husk for energy purposes.     

Biochemical and genetic engineering strategies to enhance hydrogen production in photosynthetic algae and cyanobacteria

As an energy carrier, hydrogen gas is a promising substitute to carbonaceous fuels owing to its superb conversion efficiency, non-polluting nature, and high energy content. At present, hydrogen is predominately synthesized via chemical reformation of fossil fuels. While various biological methods have been extensively explored, none of them is justified as economically feasible. A sustainable platform for biological production of hydrogen will certainly impact the biofuel market. Among a selection of biological systems, algae and cyanobacteria have garnered major interests as potential cell factories for hydrogen production. In conjunction with photosynthesis, these organisms utilize inexpensive inorganic substrates and solar energy for simultaneous biosynthesis and hydrogen evolution. However, the hydrogen yield associated with these organisms remains far too low to compete with the existing chemical systems. This article reviews recent advances of biochemical, bioprocess, and genetic engineering strategies in circumventing technological limitations to hopefully improve the applicative potential of these photosynthetic hydrogen production systems.     

Offshore wave energy generation devices: Impacts on ocean bio-environment

As the crisis of petroleum-based energy is aggravating and the carbon emission is elevating, the search and exploitation of renewable energy sources such as solar, wind and oceanic powers, are of global interest and underway in some developed countries. In western countries pioneering the oceanic energy utilization, wave is currently an attractive energy source due to the predictability and the ease to be absorbed into power grid. As wave-energy generators (WEGs) and the associated devices interact with the surrounding environment, they would have impacts on the biological components within the ecosystem in the vicinity of WEGs. However, the environmental effects of offshore WEGs on local fauna and flora have yet to be evaluated in a comprehensive way. This article discusses several aspects, including influence of offshore WEGs on marine macrofaunal communities, interactions between offshore WEGs and biofouling organisms, impacts of offshore WEGs on marine birds and of electromagnetic fields (EMFs) on marine animals as well as “artificial reef” effects. If precaution is taken with the planning and construction of offshore WEGs, and environmental monitoring is performed with operation of these devices, marine wave energy can become a desirable alternative to fossil fuels.     

Life cycle assessment of biofuels from Jatropha curcas in West Africa: a field study

In recent years, liquid biofuels for transport have benefited from significant political support due to their potential role in curbing climate change and reducing our dependence on fossil fuels. They may also participate to rural development by providing new markets for agricultural production. However, the growth of energy crops has raised concerns due to their high consumption of conventional fuels, fertilizers and pesticides, their impacts on ecosystems and their competition for arable land with food crops. Low-input species such as Jatropha curcas , a perennial, inedible crop well adapted to semiarid regions, has received much interest as a new alternative for biofuel production, minimizing adverse effects on the environment and food supply. Here, we used life-cycle assessment to quantify the benefits of J. curcas biofuel production in West Africa in terms of greenhouse gas emissions and fossil energy use, compared with fossil diesel fuel and other biofuels. Biodiesel from J. curcas has a much higher performance than current biofuels, relative to oil-derived diesel fuels. Under West Africa conditions, J. curcas biodiesel allows a 72% saving in greenhouse gas emissions compared with conventional diesel fuel, and its energy yield (the ratio of biodiesel energy output to fossil energy input) is 4.7. J. curcas production studied is eco-compatible for the impacts under consideration and fits into the context of sustainable development.     

Integrated Environmental Assessment of sunflower oil production

The high energy and petroleum based fuels demand of the world require use of alternative fuels from materials available within each country. Therefore biofuels may be an alternative to mineral diesel. A local pilot production of sunflower oil was implemented in order to test the possibility to reduce fossil fuels consumption on a local scale. Vegetable oils can be directly obtained from oilseed plants and can be used as energy sources in internal combustion engines.Environmental Impact Indicators were provided by Material Flow Accounting, Embodied Energy Analysis and Emergy Accounting. All three approaches reveal that the agricultural phase is the critical step in the whole production line from the point of view of environmental impact. The renewability calculated for the sunflower oil is 33.6%.A comparative Life Cycle Assessment analysis for the sunflower oil production line from conventional farming with organic farming showed environmental advantages.Furthermore use of vegetable oils instead of diesel oil as energy sources in internal combustion engines reduces carbon dioxide emissions of 59%.This study represents an opportunity for farms to reduce dependence on petroleum and to explore energy production systems exploiting renewable energy.     

Using microorganisms to brew biofuels

Interest in alternative fuel sources has grown in recent years in response to a confluence of factors, including concerns over our reliance on and increasing demand for fossil fuels as well as the deleterious environmental effects of fossil fuel extraction and utilization. The use of microbe-derived fuel alcohols is a viable alternative, as they are renewable, emit fewer greenhouse gasses, and require little augmentation of current energy infrastructure as compared to other sustainable transportation options such as electric vehicles and fuel cells. Here, we present a brief overview of candidate substrates for alcohol production with a focus on lignocellulosic sources, relevant microorganisms under research for industrialization and the biotechnological techniques used to improve alcohol production phenotypes.     

Photosynthesis for Food, Fuel and the Future

<正>Photosynthesis is a process that converts solar energy to chemical energy in many different organisms,ranging from plants to bacteria.Photosynthesis provides all the food we eat and all the fossil fuel we use.Photosynthesis has long been studied in order to understand its underlying mechanisms a     

Biofuels – for better or worse?

The present world population is largely fed by ‘industrialised agriculture’. This, in turn, depends on massive inputs of fossil fuels. While this energy expenditure is inescapable, it is an expensive way of ‘converting oil into potatoes'. Arguably, in view of global climate change, ever increasing population, ever increasing oil prices, ever diminishing availability of water and arable land, this is not sustainable. Despite the fact that biofuels inevitably compete for resources that might otherwise be used to grow, store and distribute food, they are frequently held to be desirable and feasible ‘green’ substitutes for fossil fuels and even that they spare carbon emissions to the atmosphere. This article challenges the absurdity of such ‘retro-agriculture’ (i.e. except in a few local circumstances) incurring yet more energy expenditure. It seeks to illustrate the misinformation on which some of the advocacy of biofuels has been based.     

Artificial photosynthesis with metal and covalent organic frameworks (MOFs and COFs): challenges and prospects in fuel‐forming electrocatalysis

Mimicking photosynthesis in generating chemical fuels from sunlight is a promising strategy to alleviate society's demand for fossil fuels. However, this approach involves a number of challenges that must be overcome before this concept can emerge as a viable solution to society's energy demand. Particularly in artificial photosynthesis, the catalytic chemistry that converts energy in the form of electricity into carbon‐based fuels and chemicals has yet to be developed. Here, we describe the foundational work and future prospects of an emerging and promising class of materials: metal‐ and covalent‐organic frameworks (MOFs and COFs). Within this context, these porous and tuneable framework materials have achieved initial success in converting abundant feedstocks (H₂O and CO₂) into chemicals and fuels. In this review, we first highlight key achievements in this direction. We then follow with a perspective on precisely how MOFs and COFs can perform in ways not possible with conventional molecular or heterogeneous catalysts. We conclude with a view on how spectroscopically probing MOF and COF catalysis can be used to elucidate reaction mechanisms and material dynamics throughout the course of reaction.