Photosynthesis for fresh water

Comments: 5 Comments
Published on: February 10, 2014

Annegret Honsbein is a post-doc in Anna Amtmann‘s lab at the University of Glasgow. As she explains in this guest post, she is working on an EPSRC project that hopes to harness the power of photosynthesis to desalinate sea water. 

Water covers more than 70% of Earth’s surface but less than 2% of it is available as freshwater. Many of the driest regions of our planet are close to the sea but irrigating fields with seawater – even if diluted – leads to build-up of salt in the soil to levels toxic to all common food crops. Current desalination technologies, such as membrane-based reverse osmosis, are successfully used in large-scale desalination plants, but they are expensive and energy inefficient.

desalinationOur multi-disciplinary EPSRC-funded project takes a synthetic biology approach to the development of an innovative desalination technology based on biological processes. We are a team of biologists and engineers from the Universities of Glasgow, Sheffield, Newcastle, Robert Gordon University at Aberdeen and Imperial College London, led by Dr. Anna Amtmann from Glasgow University.

Our idea is solar energy-fuelled desalination – with a twist. Instead of using solar panels we intend to let photosynthetic microorganisms desalinate the sea water. Cyanobacteria are ideal candidates, and we are currently working with two strains that are naturally able to adapt to a wide range of salt concentrations from fresh to sea water.

In principle, salt is toxic to all living cells, which is why most living systems have developed means to actively export sodium. In some cyanobacteria species that grow to very high densities, this ability means they actually form a low-salt reservoir within their saline environment.

We intend to use this low-salt reservoir as ion exchanger to extract the salt from the surrounding seawater. We aim to engineer cyanobacteria so we can switch off the endogenous salt export mechanism towards the end of their growth cycle, and activate a synthetic intracellular sodium accumulation unit. This synthetic unit will be assembled from membrane transport proteins evolved by different organisms to import sodium and chloride ions.

Our team’s engineers are developing techniques to manipulate the surface properties of the cyanobacteria and effectively separate the ‘salty’ cells from the desalinated water before they die, preventing release of the accumulated salt back into the ‘fresh’ water.

The final stage of the project will be to build a model version of the actual plant that could house our photosynthesis-driven bio-desalination process.

This work is published in: Jaime M. Amezaga, Anna Amtmann, Catherine A. Biggs, Tom Bond, Catherine J. Gandy, Annegret Honsbein, Esther Karunakaran, Linda Lawton, Mary Ann Madsen, Konstantinos Minas and Michael R. Templeton (2014) Biodesalination: A Case Study for Applications of Photosynthetic Bacteria in Water Treatment. Plant Physiology 164: 1661-1676; doi: http:/​/​dx.​doi.​org/​10.​1104/​pp.​113.​233973.

Image c/o Annegret Honsbein.



5 Comments - Leave a comment
  1. […] Water covers more than 70% of Earth’s surface but less than 2% of it is available as freshwater. Many of the driest regions of our planet are close to the sea but irrigating fields with seawater – even if diluted – leads to build-up of salt in the soil to levels toxic to all common food crops. Current desalination technologies, such as membrane-based reverse osmosis, are successfully used in large-scale desalination plants, but they are expensive and energy inefficient.  […]

  2. […] Annegret Honsbein explains how she plans to harness the power of photosynthesis to desalinate sea water and generate fresh water.  […]

  3. With salt being accumulated within the cyanobacteria , am sure there is a limit until which the osmotic barrier can hold. The next question is the energy intensive process of making this process into a continuous one . With accumulating salt being a stress condition for cyanobacteria doesn’t it produce any proteins which can be allergic to the user and the last question is the energy used in separation of biomass and recycling of biomass. How much percentage of cyanobacteria can effective hold this synthetic genetic circuit and how far is the replication possible without error during stress condition as this.

  4. […] Water covers more than 70% of Earth’s surface but less than 2% of it is available as freshwater. Many of the driest regions of our planet are close to the sea but irrigating fields with seawater – even if diluted – leads to build-up of salt in the soil to levels toxic to all common food crops. Current desalination technologies, such as membrane-based reverse osmosis, are successfully used in large-scale desalination plants, but they are expensive and energy inefficient.Our multi-disciplinary EPSRC-funded project takes a synthetic biology approach to the development of an innovative desalination technology based on biological processes. We are a team of biologists and engineers from the Universities of Glasgow, Sheffield, Newcastle, Robert Gordon University at Aberdeen and Imperial College London, led by Dr. Anna Amtmann from Glasgow University.Our idea is solar energy-fuelled desalination – with a twist. Instead of using solar panels we intend to let photosynthetic microorganisms desalinate the sea water. Cyanobacteria are ideal candidates, and we are currently working with two strains that are naturally able to adapt to a wide range of salt concentrations from fresh to sea water.In principle, salt is toxic to all living cells, which is why most living systems have developed means to actively export sodium. In some cyanobacteria species that grow to very high densities, this ability means they actually form a low-salt reservoir within their saline environment.We intend to use this low-salt reservoir as ion exchanger to extract the salt from the surrounding seawater. We aim to engineer cyanobacteria so we can switch off the endogenous salt export mechanism towards the end of their growth cycle, and activate a synthetic intracellular sodium accumulation unit. This synthetic unit will be assembled from membrane transport proteins evolved by different organisms to import sodium and chloride ions.Our team’s engineers are developing techniques to manipulate the surface properties of the cyanobacteria and effectively separate the ‘salty’ cells from the desalinated water before they die, preventing release of the accumulated salt back into the ‘fresh’ water.The final stage of the project will be to build a model version of the actual plant that could house our photosynthesis-driven bio-desalination process.  […]

  5. Charis Cook says:

    Hi Jeyannathann, thanks for your comment! These are all good questions. As this work is around four years in, the answers are either not yet answered or not yet released. Regarding the energy usage, I’m sure that is a key question Annegret and her colleagues are hoping to answer with the model-scale plant they intend to build. Keep an eye out for papers and/or patents!

Leave a Reply


Welcome , today is Thursday, October 23, 2014