Team:EPFL/Description
Description
Introduction
Inspired by the struggles of local winemakers as well as the preservation of agricultural land's ecosystems, we set out to develop a system designed to deal with copper pollution in water. Through an engineering approach, we researched, designed, created and tested a potential solution to this problem, and now present a proof of concept. On this page we discuss the problem at hand, our proposed solution as well as goals for the future.
The problem
Winemaking holds significant cultural importance not only in Switzerland, but in all of Europe, with Italy, France and Spain accounting for 49% of the world wine production1. Switzerland is home to 150 km2 of vineyards, 11% of which are organic cultures2. In 2007, the Lavaux vineyards in Switzerland became a UNESCO world heritage site3 due to their beauty and testimony to the longstanding cultural importance of high value winemaking in the local area. The winemaking industry is crucial to Switzerland both culturally and economically, sustaining around 1500 producers, and producing over 100 million liters of wine per year2.
Today, the disease affecting vine cultures is mildew, a parasite capable of drying out the grapes, diminishing the harvest and reportedly modifying the aroma and taste of wine4. Currently, fungicide-based treatments such as the Bordeaux mixture are the most widely used to combat mildew. This treatment is sprayed onto the leaves and has proven to be effective in diminishing the effects of this parasite. This product, widely used in Switzerland and throughout Europe5, is authorized in certified organic agriculture in various countries including Switzerland. Moreover, it is currently the only available organic option on the market6.
This organic label portrays the product as seemingly harmless to the environment, and while it may not be as harmful as other, non-organic solutions7, it does have some negative effects on the vineyards' ecosystem. Indeed, this fungicide is made with copper-sulfate, and through the action of spraying it onto the leaves, the soil is contaminated with high levels of copper5. A new layer of fungicide is applied every time enough rain falls, as the rain washes the product off the leaves and into the soil.
As a heavy metal, copper accumulates in the first 10 cm of the soil8. The accumulation then leads to a diminution of the soil's biodiversity9. In particular, copper in high concentrations is toxic to plants10, pollutes groundwater11 and is leached into the soil profile.
Research has shown this accumulation of copper in topsoil to be detrimental to new grape vines12, as shown by reduced growth in the roots and shoots. Adult grape vines, on the other hand, reportedly do not present visual symptoms of toxicity caused by copper but do accumulate copper in their perineal and annual organs. In the organic wines themselves, copper concentrations are found to be around 15 mg/l. At such a concentration, a human of 80 kg would need to drink 60 liters of organic wine a day to reach the toxicity threshold13. Our issue is thus purely an environmental one.
Copper-based fungicides are used all over the world on any leafy type of plant. The effect of these treatments on various cultures has been well documented14, 15, 16. The issue of copper contamination in soils is thus not limited to European vineyards but presents a global challenge in the field of agriculture.
Current solutions
To combat this problem, both the Swiss5 and French17 governments currently hold restrictions on the amount of copper allowed in soils. However, in 2021, there are no other options for effective organic treatments against mildew. If winemakers wish to keep the organic label and simultaneously protect their vines from mildew, they are left only with the option of a copper-based fungicide.
Remediation methods for copper contaminated soil include chemical methods, such as soil washing, biological methods, such as phytovolatilization, phytostabilization or phytoextraction and physical methods, such as soil replacement or isolation, to name a few.
According to a recent review on remediation of copper in vineyards: “Physical methods are labour intensive and costly but can be applied to highly contaminated site; chemical methods have high efficiency and effective to remove the copper, but mostly popularized in a large scale; bioremediation methods including phytoremediation and microbial remediation are appropriate for large areas of soil contaminated by low concentrations of copper. The bioremediation methods are economical, eco- friendly but time consuming.”18
Although bioremediation methods are currently being developed, most require the release of certain genetically modified organisms in nature at a large scale. This is an issue given that it is currently illegal in Switzerland to release GMOs in nature. Moreover, this problem extends to the European Union as “Nineteen out of the 27-member state countries of the European Union have voted to either partially or fully ban Genetically Modified Organisms (GMOs).”19
The problem is thus as follows: to protect grapevines from mildew, thereby ensuring the safety of the organic wine making industry, there needs to be a method capable of dealing with the problem of copper soil contamination. This method cannot allow for the release of GMOs, nor can it demand the removal and treatment of tons of soil, a practice detrimental to the winemaker's economic livelihood. This is the problem we set out to solve.
CuRe
Our goal is to prevent further contamination of agricultural soils by copper, still allowing for the use of a copper-based fungicide by winemakers. CuRe will be a way to treat rainwater carrying the copper it will have washed off the leaves previously sprayed with the fungicide. This system should demand minimal effort from current winemarkers and needs only initial installation. However, the system would work best with new and more high-tech forms of agriculture, or in new cultures, as the crops distribution could be built around this water treatment design. More information about the implementation can be found on the Hardware page.
We wanted our solution to:
- Deal with the issue of incoming copper accumulation
- Propose a realistic solution that can be safely implemented
- Advance research of heavy metal bioremediation
1. Deal with the issue of copper contamination
Our genetically modified yeast strains express copper binding proteins on their surface. While wild type yeast already absorb copper, we aim to engineer yeast to bind copper at higher concentrations. The advantage of using yeast as a vector for copper removal is its size. The adhesion of copper to yeast allows for easier filtration from rainwater – making us able to concentrate the copper so that further treatment is facilitated.
2. Propose a realistic solution that can be safely implemented
Real world problems deserve real world solutions. In reviewing possible solutions to copper contaminated soil, we found too often that projects did not account for the socio-economic needs of the people or actors most concerned. As (aspiring) engineers, we feel a responsibility to ensure that the solutions offered by science are not developed in a vacuum and, instead, take into account socio-economic factors that are critical for successful implementation. To better our understanding of the problem and properly tailor our solution, we consulted a variety of stakeholders, from local winemakers to water treatment experts. You can find information on how we did that on our Integrated Human Practices page.
Furthermore, our implementation must be based on a life-cycle approach and not create new problems for the communities we are attempting to bring aid to (overproduction of waste, release of potentially dangerous GMOs). The way in which we tackle this issue must be inclusive, considering all points of view and needs. Finally, we propose an implementation that is scalable, and applicable to different types of agriculture.
3. Advance research on heavy metal bioremediation
Heavy metal bioremediation is a growing field in microbiology, not only due to its innovations in synthetic biology, but also to the ever-growing need for solutions to heavy metal pollution of the environment. By taking advantage of synthetic biology, we strive to contribute to open-source research in this field by producing new and useful parts. To this aim, we discussed and engaged with the scientific community to come up with a new option for bioremediation that is inspired by previous research. If successful, our strategy for copper bioremediation could also be applied to other heavy metals.
The project
With our knowledge in synthetic biology, we created a yeast strain expressing copper binding proteins on its membrane surface. To this aim, we used a plasmid containing a known yeast surface display system and an endogenous yeast copper binding protein, called a metallothionein. We decided to express the protein on the membrane surface as we did not want to destabilize the yeast's intracellular chemistry by having it absorb copper. Theoretically, these copper binding proteins adhere copper to the surface of the cell membrane, thus allowing the yeast to capture more copper than the wild type strain.
Further descriptions of the project can be found on the Design page, with more detailed specificities and the research that led us to our current model.
These engineered yeasts can then be introduced into a bioreactor that was developed by our hardware subteam. CuRe's bioreactor is a simple static water system, capable of detecting water amount and regulating flow through the treatment chamber. More information concerning this aspect of the project can be found on the Hardware page.
Future prospects
Our team has thought extensively about how we could make our project better. Firstly, although our team's main inspiration was vineyards, there is potential for application of our system to other agriculture in different countries around the world. Moreover, our system could also be integrated into water treatment facilities. Indeed, in regions with strong industrial or mining activities, heavy metal pollution is very prevalent20.
As mentioned above, this same method could be adapted to other heavy metal binding proteins. The adaptability of our system, as well as a need for such a system to combat heavy metal pollution, are the key reasons our project is so strong.
On the relevant pages of our wiki, you can find more precise improvements we wish to implement.
References
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2020 wine product report, First Estimates
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L'année viticole 2020, Statistiques vitivinicoles
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Lavaux, Vineyard Terraces
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Effects of Powdery Mildew on Vine Growth, Yield, and Quality of Concord GrapesPlant Disease, vol. 85, no. 2, pp. 137-140
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Potential Sources of Anthropogenic Copper Inputs to European Agricultural SoilsSustainability, vol. 10, no. 7, pp. 2380
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Are there alternatives to copper for controlling grapevine downy mildew in organic viticulture?Crop Protection, vol. 30, no. 7, pp. 776-788
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Environmental Impact of Different Agricultural Management Practices: Conventional vs. Organic AgricultureCritical Reviews in Plant Sciences, vol. 30, no. 1-2, pp. 95-124
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Copper distribution in European topsoils: An assessment based on LUCAS soil surveyScience of The Total Environment, vol. 636, pp. 282-298
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Thirteen decades of antimicrobial copper compounds applied in agriculture. A reviewAgronomy for Sustainable Development, vol. 38, no. 3
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Effects of elevated soil copper on phenology, growth and reproduction of five ruderal plant speciesEnvironmental Pollution, vol. 122, no. 3, pp. 361-368
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Leaching of copper, chromium and arsenic from treated vineyard posts in Marlborough, New ZealandScience of The Total Environment, vol. 364, no. 1-3, pp. 113-123
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Copper uptake, accumulation and physiological changes in adult grapevines in response to excess copper in soilPlant and Soil, vol. 374, no. 1-2, pp. 593-610
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Un pesticide présent dans 100 % des vins bioAgriculture et environnement
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The potential impact of long-term copper fungicide usage on soil microbial biomass and microbial activity in an avocado orchardSoil Research, vol. 40, no. 5, pp. 749
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Microbial and enzyme properties of apple orchard soil as affected by long-term application of copper fungicideSoil Biology and Biochemistry, vol. 41, no. 7, pp. 1504-1509
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Accumulation and availability of copper in citrus grove soils as affected by fungicide applicationJournal of Soils and Sediments, vol. 11, no. 4, pp. 639-648
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Liste des critères d'octroi des autorisations exceptionnelles, Producteurs
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Remediation Technology for Copper Contaminated Soil: A ReviewAsian Soil Research Journal, pp. 1-7
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Several European countries move to rule out GMOs
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Effects of mining wastewater discharges on heavy metal pollution and soil enzyme activity of the paddy fieldsJournal of Geochemical Exploration, vol. 147, pp. 139-150