Fuel Gas Storage:The Challenge of Methane

Methane usage, as part of the overall energy mix, has been gradually increasing in the last few decades and the exploration and production of shale gas reserves indicates that this trend is likely to continue. Upcoming energy demand, due to population and economic growth around the world will put a severe strain on the conversion of primary energy, a reason why shale gas is predicted to be intensely explored in coming years. Shale gas, despite health and environmental concerns, is expected to create a million jobs and add £1 trillion to the European Union economy. State-of-the-art methane storage is either as a compressed gas (usually at 25 MPa) or as a liquid (as Liquefied Natural Gas, LNG, with densities of ~450 kg m-3 at -162 °C), with the overall aim of increasing the volumetric density of the methane. Both technologies, however, incur large energy penalties due to the operational constraints of attaining high pressures and/or extremely low temperatures. The advances made in gas sorption in porous materials in recent decades suggest that this technology can be a competitive alternative to current state-of-the-art methods. This is due to considerable interactions between methane and optimally tailored porous structures, even at room temperature, which enhance the density of the gas on the surface of the solid structure. A rigorous experimental programme for prospective adsorbent materials for methane storage was carried out and the results analysed, with a view to directly comparing adsorptive storage technologies with other competing alternatives. The materials analysed were the high-surface area metal-organic frameworks MIL-101 and Cu-BTC and the activated carbon AX-21. The adsorbed methane densities obtained in some of these materials, even at room temperatures and mild operating pressures, indicate that there is definite scope for high-surface area materials to be used as alternatives to achieve high volumetric energy density and even compete with LNG technologies in terms of high methane densities per unit volume

Anchoring of proteins to lactic acid bacteria

The anchoring of proteins to the cell surface of lactic acid bacteria (LAB) using genetic techniques is an exciting and emerging research area that holds great promise for a wide variety of biotechnological applications. This paper reviews five different types of anchoring domains that have been explored for their efficiency in attaching hybrid proteins to the cell membrane or cell wall of LAB. The most exploited anchoring regions are those with the LPXTG box that bind the proteins in a covalent way to the cell wall. In recent years, two new modes of cell wall protein anchoring have been studied and these may provide new approaches in surface display. The important progress that is being made with cell surface display of chimaeric proteins in the areas of vaccine development and enzyme- or whole-cell immobilisation is highlighted.