A global phosphate problem
The city of Düsseldorf is crossed by the river Itter, one of the most polluted rivers in Germany (Schmidt 2015). We wanted to find a way to improve this situation, so we tried to look at the causes of this pollution. A big part of the problem is the phosphate in the river, which leads to algal blooms, leading to hypoxia and the release of toxins into the environment (Prasad & Prasad, 2019). An investigation from the UNEP (United Nation Environmental Protection) showed that 30-40% of all lakes in the world already suffer from eutrophication and with an estimated increase of fertilizer usage, the number is likely to grow (Herschy et al, 2012).
When doing our research, we discovered that most of this phosphate was coming from the widespread use of phosphate fertilizers in agriculture (Cordell et al. 2009). However, a growing world population has a growing demand for food, and therefore a growing demand of phosphate fertilizers, as shown in Table. 1 (Cordell et al. 2009).
Fertile soil is characterised by the presence of a balanced proportion of all essential nutrients for plants. While some ecosystems suffer from nutrient imbalance due to natural factors, almost all agricultural soils suffer from an imbalance due to the big quantities of nutrients removed during the harvest, which has serious effects on plant growth. Hence, farmers are forced to add fertilizers to the soil to sustain and enhance plant growth (FAO, 2019).
However, the largest source of phosphate, phosphate rock, is a non-renewable resource, which is expected to be depleted by the end of the century (Cordell 2010), ( White 2000). This means that sustainable agriculture can not be reliant on phosphate rock and there is a dire need for methods of safely recycling phosphate.
A sustainable solution
The main goal of Mossphate is to provide a sustainable synthetic biology approach to close the phosphate cycle by genetically engineering the moss Physcomitrella patens for an enhanced uptake and accumulation of phosphate. To achieve this aim, we established 3 specific milestones:
1. Improve phosphate storage in the form of polyphosphate granules.
2. Test the accumulation of polyphosphate in the cytosol and the vacuole.
3. Enhance phosphate uptake capacity of P. patens.
These milestones can be achieved by modifying P. patens and testing both the intracellular phosphate concentration and the remaining phosphate in the medium. To better deal with the stress of phosphate accumulating in the cells, directing the polyphosphate kinases to the vacuole is a viable strategy. Further enhancements to the high-phosphate P. patens strain through phosphate importers are an important last step, as the fertilizer market is based around cost efficiency and we believe that making a competitive product is the best way to create sustainable agriculture.
Ideally, our project could be used to create a new last-stage in wastewater treatment facilities. A reduction in the phosphate content of the outgoing clean water would have a positive impact and lead to a reduction of eutrophication and its negative impacts on the environment.
At the same time, the phosphate-rich P. patens could be dried and used as a fertilizer, as shown in Fig. 3.
Mossphate would provide a more sustainable and environmentally-friendly methodology for phosphate recycling from wastewater by using moss as a fertilizer and at the same time, contribute to the establishment of P. patens as a biotechnological chassis.
Cordell, D. (2010). The Story of Phosphorus Sustainability implications of global phosphorus scarcity for food security. Environmental Studies. Retrieved from http://swepub.kb.se/bib/swepub:oai:DiVA.org:liu-53430?tab2=abs&language=en
Cordell, D., Drangert, J.-O., & White, S. (2009). The story of phosphorus: Global food security and food for thought. Global Environmental Change, 19(2), 292–305. https://doi.org/10.1016/J.GLOENVCHA.2008.10.009
Food and Agriculture Organization of the United Nations (FAO). (2019). World Fertilizer Trends and Outlook to 2022.
Herschy, R. W., Herschy, R. W., Wolanski, E., Andutta, F., Delhez, E., Fairbridge, R. W., … Fontaine, T. D. (2012). Eutrophication in Fresh Waters: An International Review. Encyclopedia of Earth Sciences Series, 258–270.
Prasad, R., & Prasad, S. (2019). Algal Blooms and Phosphate Eutrophication of Inland Water Ecosystems with Special Reference to India. International Journal of Plant and Environment, 5(01), 1–8. https://doi.org/10.18811/ijpen.v5i01.1.
Schmidt, C. (2015). Die Itter: Lebensader und Abwasserkanal zugleich. Retrieved from https://www.wz.de/nrw/kreis-mettmann/haan-und-hilden/die-itter-lebensader-und-abwasserkanal-zugleich_aid-25007317. Last access: 25.10.2020.
White, J. (2000). Introduction to Biogeochemical Cycles. In (Ch. 4) (p. Department of Geological Sciences, University of C).