Bio-desalination: from cell to tap

Lead Research Organisation: University of Glasgow
Department Name: College of Medical, Veterinary &Life Sci

Abstract

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.

Planned Impact

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.

Publications

10 25 50
 
Description A consortium of biologists and engineers was formed to investigate possibilities to use biological organisms to desalinate water (biodesalination). In this exploratory grant we have obtained a proof of principle that we can use photosynthetic microorgansims to remove salt (NaCl) from seawater. The most important milestones achieved are summarised below:
1. An initial screen of candidate microorganisms identified two cyanobacterial strains (Synechocystis PCC 6803 and Synechococcus PCC 7002) as useful chassis for engineering a biodesalination process, based on (a) tolerance of a wide range of external salinity levels, (b) fast growth, (c) availability of genome sequence and (d) successful genetic transformation. We have optimised growth kinetics of these strains by systematically varying environmental factors such as day/night rhythm, light intensity and quality, O2, CO2 and mineral nutrient supply. For PCC 6893 we obtained a maximal cell density of 5.5x1013 cells/litre, providing a combined cell volume of 0.45 litres and a total cell surface of 1000 m2.
2. We have cloned several genes encoding light-powered ion pumps (e.g. halorhodopsin from Nitronomonas pharaonis), and successfully expressed them in PCC 6803 and PCC 7002. We have developed a functional assay to measure light-induced membrane hyperpolarisation in the transformed cells.
3. Using a range of biophysical and biochemical techniques we have characterised cell surface and cell aggregation properties in PCC 6803 and PCC 7002. We have also determined the biochemical composition of extracellular polymeric substances (EPS) and we have carried out a preliminary analysis of the EPS proteome in the two strains. This research has pinpointed several candidate proteins that determine EPS properties.
4. We have developed evidence-based protocols for cell/water separation and disinfection. We have shown that coagulation and ultrafiltration of PCC 6803 and PCC 7002 are effective for cell-liquid separation.
5. We have designed a process that accommodates and links the different phases of biodesalination (growth, desalination, cell/liquid separation), and we have tested the process at bench scale.
6. Using high-density cell suspension followed by cell/water separation we were able to remove substantial amounts of sodium and chloride from seawater. Based on our evidence to date, the phenomenon is due to both adsorption (chelating by EPS) and intracellular accumulation (driven by electrochemical gradients) but at this stage the exact relative contribution of the two processes remains to be quantified.
7. We have carried out a literature research of public acceptance issues that need to be addressed before implementation of the new technology. We have carried out a first hazard analysis and determined critical control points of the biodesalination process.
Our pioneering work opens an opportunity for 'green' desalination technology. To translate our laboratory findings into a robust technology, additional research is needed to understand, control and improve the kinetics and capacity of salt uptake and accumulation in the generated cyanobacterial strains.
Exploitation Route Our co-authored paper "Biodesalination: a case study for applications of photosynthetic bacteria in water treatment" (Amezaga et al. 2014, Plant Physiol, 164, 1661-1676) was met by a stream of enquiries from different industries, expressing their interest in the technology. Subsequent exploratory meetings confirmed that our research is highly promising and has enormous potential for spin-off and/or licencing, not just related to its core application in water desalination but for other applications of the generic tools, materials and processes generated. The communication to date has provided strong evidence that the development of biodesalination technology can contribute to UK economic success and enable future development of key emerging industries with particular emphasis on water treatment, marine industries and production of biomass/biomaterials.
Sectors Agriculture, Food and Drink,Energy,Environment,Manufacturing, including Industrial Biotechology

 
Description Business Interaction Voucher
Amount £10,000 (GBP)
Funding ID IBCarb-BIV- 0316-015 
Organisation IBCarb 
Sector Charity/Non Profit
Country Unknown
Start 07/2016 
End 05/2017
 
Description Efficacy study of product in salt conditions FSA 249
Amount £5,000 (GBP)
Organisation Scottish Enterprise 
Sector Public
Country United Kingdom
Start 04/2014 
End 10/2014
 
Description IBioIC PhD studentship
Amount £44,876 (GBP)
Organisation IBioIC 
Sector Academic/University
Country Unknown
Start 10/2016 
End 09/2020
 
Description Identification of stage-specific promoter elements in photosynthetic bacteria (ISSF Catalyst)
Amount £15,725 (GBP)
Organisation Wellcome Trust 
Department Wellcome Trust Institutional Strategic Support Fund
Sector Charity/Non Profit
Country United Kingdom
Start 10/2014 
End 06/2015
 
Description Biodesalination consortium 
Organisation Imperial College London
Country United Kingdom 
Sector Academic/University 
PI Contribution Prof. Anna Amtmann is PI of the Biodesalination consortium.
Collaborator Contribution Dr. Michael Templeton (Imperial) is co-I in the Biodesalination consortium.
Impact See outputs of EPSRC grant.
Start Year 2011
 
Description Biodesalination consortium 
Organisation Newcastle University
Country United Kingdom 
Sector Academic/University 
PI Contribution Prof. Anna Amtmann is PI of the Biodesalination consortium.
Collaborator Contribution Dr. Jaime Amezaga (University of Newcastle) is co-I in the Biodesalination consortium.
Impact See outcomes of EPSRC grant.
Start Year 2011
 
Description Biodesalination consortium 
Organisation Robert Gordon University
Country United Kingdom 
Sector Academic/University 
PI Contribution Prof. Anna Amtmann is PI of the Biodesalination consortium.
Collaborator Contribution Prof. Linda Lawton (RGU) is co-I in the Biodesalination consortium.
Impact See outputs of EPSRC grant.
Start Year 2011
 
Description Biodesalination consortium 
Organisation University of Sheffield
Country United Kingdom 
Sector Academic/University 
PI Contribution Prof. Anna Amtmann is PI of the Biodesalination consortium.
Collaborator Contribution Prof. Catherine Biggs (Sheffield UNiversity) is co-I in the Biodesalination consortium.
Impact See outputs of EPSRC grant.
Start Year 2011
 
Description "Meet the Expert" at the Glasgow Science Centre 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Members of the Amtmann lab set up a display that demonstrated the importance of light for growth of both plants and cyanobacteria. Children built phycobilisomes, the light-harvesting complexes in cyanobacteria, using different coloured pigments. For the enthusiastic ones, we designed a take-home experiment comparing plant growth in the light versus the dark.
Year(s) Of Engagement Activity 2010,2016
URL http://www.glasgowsciencecentre.org/support-us/meet-the-expert.html
 
Description EPSRC Water Showcase 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact The biodesalination project was represented by a poster and received a lot of interest.

Industrial contacts.
Year(s) Of Engagement Activity 2012
 
Description IBioIC Annual Conference 2018 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Mary Ann Madsen (Amtmann group) gave a talk as invited session speaker (Synthetic Biology)
Year(s) Of Engagement Activity 2018
URL http://www.ibioic.com/news_and_events/annual_conference/d1066/
 
Description Invited talk at IBCarb/PhycoNet (BBSRC NIBBs) 'Algal Polysaccharides' meeting (Edinburgh, July 2016): 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Invited talk "Cyanobacteria as a chassis for synthetic biology approaches to glycobiology".
IBCarb/PhycoNet (BBSRC NIBBs) 'Algal Polysaccharides' meeting (Edinburgh, July 2016):
An opportunity to interact with members of Industry.
Year(s) Of Engagement Activity 2016
URL http://ibcarb.com/wp-content/uploads/IBCarb_PHYCONET-Algal-polysaccharides-agenda.pdf
 
Description Poster presentation IBioIC Annual Meeting (Glasgow January 2016) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Mary Ann Madsen presented a poster pn her PhD work ('Growth-Phase Specific Promoters of Cyanobacteria for Synthetic Biology Applications' at the IBioIC Annual Meeting (Glasgow January 2016)/ We used the event to network with Industry such as Ingenza, Xanthella and Glycomar. As a result of this we successfully applied with Glycomar for a Business Interaction Voucher from IBCarb.
Year(s) Of Engagement Activity 2016
URL https://www.ibioic.com/index.php
 
Description Primary School age children workshops (Aberdeenshire) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Developed greater interest in aspects of water scarcity and discussion about the right to drinking water access.

Many of the children reported that they had discussed the workshop with family and friends including re-enacting some of the activities.
Year(s) Of Engagement Activity 2012,2013,2014