Engineered clostridial [FeFe]-hydrogenase shows improved O2 tolerance in Chlamydomonas reinhardtii

Hydrogenase intolerance to oxygen remains a critical hurdle on the road to photosynthetic hydrogen production for sustainable energy demands. Although the engineering of the intrinsic oxygen tolerance mechanism of hydrogenase using mutagenesis is an ambitious approach, recent in-vitro studies reported a novel and improved synthetic [FeFe]-Hydrogenase variants. To corroborate these findings in-vivo, we expressed either an engineered variant or its cognate wild type enzyme in the chloroplast genome of Chlamydomonas reinhardtii. We characterized their activity using a customized photosynthetic hydrogen production in-vivo assay to test whether the improved variant could maintain a greater fraction of its activity following oxygen exposure. We found that the mutated variant exhibited a superior oxygen tolerance while persevering its photosynthetic performance in terms of hydrogen production yield. Importantly, we show for the first time that this approach can potentially address the inherent O₂ sensitivity of [FeFe]-Hydrogenases for photosynthetic hydrogen production.     

Applications of enzymatic biofuel cells in bioelectronic devices – A review

In this review paper, the authors have presented a brief conceptual summary of the applications of biofuel cell in general and enzymatic one in special with a short historical background, rather than their design and operation. Greater emphasis has been given to the recent progress in the development of biofuel cells and their applications for powering bioelectronic devices. Importance of electronic management of the energy derived from biological sources and interfacing enzyme-based biofuel cells with power consuming microelectronic devices have also been discussed briefly. The applications of the enzyme in the advancement of anode and cathode of biofuel cells based on the classification of single-enzyme and multi-enzyme catalysis system have also been briefly reviewed. In addition, the role of nanotechnology accompanied with redox mediators in enhancing the power output of enzymatic biofuel cells has been discussed with the help of some notable research efforts made recently with a particular emphasis on some of the latest and most imperative breakthroughs in EBFCs design based on buckypapers and carbon nanodots. The progress in implantable and self-powered bioelectrochemical devices with special heed to latest advances have been summarized in the light of several briefly described research contributions made in recent years. Moreover, the long-term stability and factors influencing the catalytic activity of enzymes in EBFCs have been reviewed in the context of the implantable and wearable application of these power sources. Finally, its prospects along with the prevailing scientific and technical challenges that will need to be resolved in the future for realizing their practical applications are discussed briefly.     

Optimal strategies for biomass productivity maximization in a photobioreactor using natural light

We address the question of the optimization of the microalgal biomass long term productivity in the framework of production in photobioreactors under the influence of day/night cycles. For that, we propose a simple bioreactor model accounting for light attenuation in the reactor due to biomass density and we obtain the control law that optimizes productivity over a single day through the application of Pontryagin’s maximum principle. The dilution rate is the main control, the input concentration being only used as the secondary control to maintain the substrate concentration high. An important constraint on the obtained solution is that the biomass in the reactor should be at the same level at the beginning and at the end of the day so that the same control can be applied everyday and optimizes some form of long term productivity. Several scenarios are possible depending on the microalgae’s strain parameters and the maximal admissible value of the dilution rate: bang–bang or bang–singular–bang control or, if the growth rate of the algae is very strong in the presence of light, constant maximal dilution. A bifurcation diagram is presented to illustrate for which values of the parameters these different behaviors occur. Finally, a simple sub-optimal bang–bang strategy is proposed that numerically achieves productivity levels that almost match those of the optimal strategy.     

纳米材料在生物燃料电池中的应用

酶生物燃料电池的寿命短以及能量密度低都与酶的稳定性、电子迁移速率和酶载量相关。采用纳米粒子、纳米纤维和介孔介质作为酶固定化的支持物,由于纳米材料巨大的表面可以增加酶载量和促进反应的发生,从而提高生物燃料电池的能量密度。将纳米材料应用于酶生物燃料电池的酶催化剂的固定,在完善电池性能上具有很大的发展潜力。     

Development of a membraneless ethanol/oxygen biofuel cell

Biofuel cells are similar to traditional fuel cells, except the metallic electrocatalyst is replaced with a biological electrocatalyst. This paper details the development of an enzymatic biofuel cell, which employs alcohol dehydrogenase to oxidize ethanol at the anode and bilirubin oxidase to reduce oxygen at the cathode. This ethanol/oxygen biofuel cell has an active lifetime of about 30 days and shows power densities of up to 0.46 mW/cm². The biocathode described in this paper is unique in that bilirubin oxidase is immobilized within a modified Nafion polymer that acts both to entrap and stabilize the enzyme, while also containing the redox mediator in concentrations large enough for self-exchange based conduction of electrons between the enzyme and the electrode. This biocathode is fuel tolerant, which leads to a unique fuel cell that employs both renewable catalysts and fuel, but does not require a separator membrane to separate anolyte from catholyte.     

Solid contents of palm‐based biofuel mixtures with respect to storage and handling

The solid content (SC) of biofuel mixtures obtained from mixing crude palm oil (CPO) with medium fuel oil (MFO), and refined palm oil (RPO) with petroleum diesel (PD), was investigated. The SC of these mixtures will impact on their applications, storage and handling. The concentrations of CPO and RPO in the investigated mixtures ranged from 5 to 90% for the CPO‐MFO system and from 0 to 10% for the RPO‐PD system. For CPO/MFO mixtures, their SC exhibited eutectic behavior over the temperature range measured (5–20 °C). Eutectic minima were observed in the 80–90% CPO concentration range for all temperatures. These eutectic minima are due to dilution effects and the formation of van der Waals hydrogen bonds between the asphaltenes in MFO and the triacylglycerols. RPO/PD mixtures did not show any eutectic behavior. The SC for the RPO/PD mixtures were observed to be below 4% at 5 °C after 24 h of tempering and 0% at 15 °C over the same tempering period. When semi‐solid, ambient PO is used as a biofuel, heating is required to liquify it for ease of handling. When mixed with petroleum‐based fuels in the correct proportion, present handling and storage equipment and facilities are adequate for handling these mixtures.     

Detailed analysis on emission and performance characteristics of neat biofuel-fuelled diesel engine

ABSTRACT

There is an entanglement over the rapid exhaust of fossil fuel and soreness of environmental changes. Biofuels are acting as an alternative resource for petroleum products and also salve of emissions control and engine performance improvement. Scholars have seen the supreme use of bio-fuel apparent, as it will influence greenhouse effect. Investigation results show the diminished heating value in congruence with conventional pabulum, so it had depleted more in brake mean effective-fuel power ratio and proliferated NO_x compared with diesel fuel. The article mainly focuses on the selection – process of biofuel and analysis of performance (BSFC, EGT and brake thermal efficiency), emissions (CO, NO_x, CO₂, PM and HC) and combustion (NHR and CP) of the engine are exclusively discussed and summarised. Finally, stability, opportunity, and restraint of a selection of alternative fuel and investigation and study on the engine were asserted to guide further future exploration and evolution in that domain.     

Critical analysis of the European Union directive which regulates the use of biofuels: An approach to the Spanish case

For more than a decade we have lived in a period where the so-called “sustainability” is crucial and is motivated primarily by the social awareness of achieving a balance between human development and the conservation of the environment. This philosophy has a direct and inevitable impact on business and politics. Governments have long since been developing standards and encouraging various diverse initiatives whose aim is to defend the environment.In recent times, the global debate on the environment has been centred on CO₂ emissions. This gas is the major cause of the “greenhouse effect” and people are more concerned with the idea that the emissions of this gas should be minimized. As a result of this concern, the Kyoto Protocol was enacted and subscribed to by many countries, setting the maximum gas emissions for them.Fossil fuels are a major source of CO₂ emissions. In 2003 the European Union (EU) directive 2003/30/EC [2003/30/EC Directive of the European Parliament and the Council—8th may 2003. On the promotion of the use of biofuels or other renewable fuels for transport] was developed with the aim of promoting the use of biofuels as a substitute for diesel or petrol among European Union countries as well as to contribute to fulfilling the commitments on climate change, security of supply in environmentally friendly conditions and the promotion of renewable energy sources.In order to achieve these goals, the directive forces all EU members to ensure that at least 5.75% of all petrol and diesel fuels sold for transport purposes are biofuels before December 31 of 2010. European Union countries have social and economic characteristics unique to themselves. The energy dependence from foreign sources, the features of the agricultural sector or the degree of industrialization varies greatly from one country to another. In this context, it is questionable whether the obligation imposed by this directive applies to achieve uniform and/or identical goals in each of the countries involved and whether the actions of the various governments are also aligned with these goals.     

A green catalyst for biodiesel production from jatropha oil: Optimization study

In this study, a simple and solvent-free method was used to prepare sulfated zirconia-alumina (SZA) catalyst. Its catalytic activity was subsequently investigated for the transesterification of Jatropha curcas L. oil to fatty acid methyl ester (FAME). The effects of catalyst preparation parameters on the yield of FAME were investigated using Design of Experiment (DOE). Results revealed that calcination temperature has a quadratic effect while calcination duration has a linear effect on the yield of FAME. Apart from that, interaction between both variables was also found to significantly affect the yield of FAME. At optimum condition; calcination temperature and calcination duration at 490 °C and 4 h, respectively, an optimum FAME yield of 78.2 wt% was obtained. Characterization with XRD, IR and BET were then used to verify the characteristic of SZA catalyst with those prepared using well established method and also to describe the catalyst characteristic with its activity.