Bio-desalination: from cell to tap

While three quarters of the earth's surface is covered in water almost all of it is present in the oceans with less than 0.5 % available as freshwater. Increasing global population, industrialisation and particularly agriculture exert significant pressures on this limited resource. With the aim to unlock the vast water resource in the oceans, attention for some time has focussed on the potential desalination of seawater to provide freshwater. However, current desalination technology, based on physicochemical processes, is a highly energy demanding process and its application is limited to fuel-rich and/or affluent developed countries. In this project we turn to biological mechanisms to remove sodium chloride (NaCl) from seawater ('bio-desalination'). We will exploit the fact that marine organisms employ energy-consuming transport processes to maintain low sodium concentrations inside their cells. The energy for this natural desalination ultimately comes from sunlight harvested by photo-autotrophic organisms at the bottom of the marine food chain. Based on available information on ion flux rates through individual transport proteins and their abundance in cell membranes, and taking into account the total cell surface area and volume generated by high-density bacterial cultures, we propose that the energized low-sodium internal volume of microbial cultures can be used as an ion exchanger to remove NaCl from the surrounding seawater.

In a multi-pronged, integrated work programme led by a team of experts from different disciplines (microbiology, biophysics, molecular biology, environmental engineering and process engineering) we will generate the biological tools that will enable us to control membrane transport in marine bacteria, and we will design a simple and energy-efficient process for growth, exposure and removal of the bacterial cultures in/from the seawater. We will further maximise both the training potential and the potential impact of this innovative and multidisciplinary programme through staff exchange programmes, Social Impact Assessment and involvement of an Advisory Board which includes representatives of water industries and charities working in developing countries.

The work comprises five work packages: 1.We will select a suitable isolate of marine cyanobacteria and identify environmental conditions (e.g. pH, carbon supply) that can act as on/off triggers for endogenous Na-export. 2. We will adjust the activity and biophysical properties of light-energized, retinal Cl-pumps and Na-channel proteins to generate a functional 'salt-accumulator for subsequent expression in the cyanobacteria under the control of an inducible promoter. 3. We will analyse the effect of environmental conditions (including salinity) on chemical and physical cell-wall properties and develop a controllable cell-aggregation protocol to facilitate rapid removal of the cyanobacteria from the desalted water. 4. We will assemble a prototype process engineering solution that combines the different biological phases of bio-desalination, and we will build a bench-scale model. 5. We will carry out a thorough assessment of social impact, demands, risks and policy implications of this new technology.

The project addresses several fundamental challenges in different areas of modern biology and engineering. The groundbreaking advances made over recent years in synthetic biology and bioreactor technology have created an exciting research environment for tackling these challenges now with a realistic chance of success. Furthermore, bio-desalination technology lends itself to be combined with downstream industrial uses of the harvested microorganism e.g. the production of bio-fuel and extraction of bio-compounds for cosmetics and medicine. The potential benefit for society is evident as the proposed technology harvests the enormous energy that is encapsulated in autotrophic marine life, biological membranes and ion gradients.

Water scarcity is a global problem threatening the provision of food, drinking water and sanitation for a growing world population. The limited availability of freshwater is contrasted by a huge volume of seawater in our oceans. Unlocking the water resource of our oceans provides an immense opportunity to transform the lives of many people worldwide. However, current desalination technologies rely on expensive, specialised equipment and a high input of energy and are therefore not sustainable.

This project aims to address this challenge by developing a prototype for desalination of seawater using biological processes. While the outcome of this 3-year project is expected to be a proof of principle, the impact that this new technology could ultimately have on people's lives, particularly in water-scarce, low-income countries which cannot afford the currently available desalination technologies, was the original motivator of the proposal. We are not interested in developing a sophisticated and expensive technical solution that proves ultimately useless in the field! With this in mind, the team and work programme have been specially assembled such that they represent a pathway to impact in themselves - i.e. we will create a continuous pipeline of knowledge transfer from the biology laboratory discoveries to the process engineering solution, and we will take societal issues into account at all stages of the research.

The potential applications of the methodology developed in this project are broad and the potential pathways for exploitation are multiple. Stakeholders include a number of industries (e.g. (bio-) technology, natural products, oil, water treatment and distribution; UK and abroad), governments, communities, and development charities, and, at the other end of the spectrum, fundamental and applied scientists in academic institutions worldwide. To ensure that the needs and interests of stakeholders are incorporated with the project's research direction and thereby maximise the impact of the project, we have created an Advisory Board with members including representatives from academia, the UK water industry, and international development charities.

The potential for exploitation of the technologies developed on this project will be maximised through the diverse industrial links and collaborations that the co-PIs have already established. The PI and co-PIs' Universities operate administrative services that will assist us with the necessary contracts (e.g. IP arrangements) between ourselves and with any industrial partners who may be beneficial to be brought onboard at some point in the project.

Diverse means of public communication and engagement will be used, including (i) involvement with school projects (ii) contribution to general science sections in newspapers and magazines, (iii) radio and television interviews, (iv) podcasts and web pages, (v) open days and laboratory tours, (vi) exhibitions and children's events in museums and science centres. Also, the 3:2 representation of female (co-)PIs in the team sets an encouraging example to female students in SET subjects, and supports ongoing efforts to promote women as leaders in SET.

The project will also have impact in terms of training high quality research associates (RAs), who will have the opportunity to learn about conceptual approaches and methodologies employed in other research disciplines. We will maximally exploit the training potential of the project by encouraging visits and training periods of the RAs in the different groups.

Ultimately, the most significant impact of this project is that it will involve research at the forefront of science and engineering and is expected to lead to high-impact publications and innovations with the aim of contributing a new piece of the solution to the huge current and future challenge of global water scarcity.