Team:XMU-China/Implementation
This year, we focused on providing a convenient solution for institutions and individuals in the tea product industry chain to analyze glyphosate residues in tea product, so that those who do not have professional biologic and chemistry knowledge can monitor the “health status” of their tea product just like people measure their blood pressure with an automatic sphygmomanometer at their home.
Beyond analysis of glyphosate residues, we extend our goal to help farmers more quickly degrade the glyphosate that may remain in the tea garden through synthetic biology strategy. Once our terminal users found glyphosate residue in their sample exceed the maximum residue limit allowed, they could boot the glyphosate degradation equipment to “purify” the soil for tea growing.
In order to realize our proposal, we designed and made a prototype device for portable analysis for glyphosate. Our device comprises a few basic components: bacteria incubator, reaction chamber and fluorescence analyzer. Enzymatic reactions happen inside the reaction chamber and information convert into fluorescence signal detected by signal processor; the intensity of the fluorescence is significant because it is proportional to the concentration of glyphosate in the analyte which is ultimately the information that we desire.
What’s more, we hope that the analysis procedure can be executed easily, so we developed a mobile application platform for instrument operating. Data exchange between mobile application and our device via Bluetooth® technology. So terminal users can realize real-time monitoring of the analysis procedure and obtain the output analytical result through the related application.
As for our glyphosate degradation equipment, we expect that our engineered bacteria solution be sprayed into the soils with excess glyphosate directly, the engineered bacteria then will absorb glyphosate and degrade it intracellularly.
Our target users cover every link of tea production and sales chain, including the initial producers, processors at all levels and final distributors, and also include the regulatory authorities that maintain market order.
In the process of tea planting, the use of herbicides is essential. The complete prohibition of herbicides will greatly increase the production cost and reduce the quality of tea. Glyphosate is a kind of herbicide with clear effect and low price, so it is unrealistic to completely prohibit its usage. However, once the glyphosate residue in the product is found to exceed the maximum residue limit, tea farmers will face the risk of losing market competitiveness or even taking legal responsibility. This is the dilemma faced by tea farmers at present. One of the main reasons for this problem is that the existing detection methods are difficult to popularize to the most basic production links. Our detection method has the advantages of simplicity and portability, and it is very convenient to popularize. Considering tea farmers' pursuit of product quality, reputation and production profit, they should be our primary target users.
Tea is widely planted all over the world, so it is obviously unrealistic to use traditional methods(LC-MS/MS) for large-scale detection. The traditional method is complicated in operation and slow in detection, which directly limits the efficiency of the quality inspection department in detecting glyphosate residual in tea products. Our analytical method can greatly improve the detection speed, thus improving the detection efficiency of relevant departments and expanding the detection range. Therefore, considering the demand of quality supervision departments for further regulating market order and protecting consumers' health rights and interests, they are also part of our target users.
In the sales of tea products, it is difficult for consumers to deal directly with tea farmers, but with distributors. Therefore, in a sense, the distributor should bear the most direct responsibility for the quality of the products sold. However, unless a professional quality inspection agency is entrusted for inspection, the distributor knows nothing about whether glyphosate in the purchased products exceeds the standard. Therefore, due to the lack of information, tea dealers take great risks in the whole transaction process. Our analytical instrument can eliminate this kind of distort of communication to a great extent, so that distributors can know the quality of products when purchasing goods, so there is no doubt that tea distributors will become one of our target users.
Similar to tea distributors, tea processors at all levels bear the risks brought by the uncertainty of raw material quality, so they are also one of our target users.
Our glyphosate analysis device will be delivered with reagents kit included. Once users received our glyphosate analysis device, they just need to take few steps to accomplish their analysis procedure. A set of reagent kit contains 3 kinds of solutions and 2 types of encapsulated freeze-dried engineered E. coli strains. Materials required but not provided only contains tea products to be analyzed and users just need to take 6 steps to finish sample loading for one test.
Matched with the detection hardware is our own application for Android platforms. Users can download it on their mobile phone. Before using our glyphosate analysis device, users should turn on Bluetooth® and pair with the analysis device. After opening the detection page, users can follow the steps provided on the screen preparing for detection, which means that the operation progress is easily-using to every group. While the device is working, users can learn the time left on the screen.
The analytical report will be given after device finishes analyzing, users can save or share their report as they like. All the information is stored in the database which is in the cloud server in case of data loss.
For both our detection and degradation devices, we have to face the danger of bacteria release into the natural environment. In our design, we put several kill switches to ensure the engineered bacteria could not live out of cultivation environment. For our detection device, we designed two well-regulated system for biosafety.
Plan A
We designed a complex balanced system constructed by multiple promoters and their inducers or repressors. Through different induction, (like when aTc is added, the inhibited state of the PLtetO promoter will be stopped and lacI gene will starting expression, thereby Ptrc2 and Ptrc2-d promoters will be inhibited and engineered bacteria will alive), the balance brakes and the engineered bacteria will be killed.
Plan B
By using inverters, we can make engineered bacteria survive when certain substances are present, but die when they do not exist. By adding arabinose to the culture medium into the device so that it can survive. Once engineered bacteria escape to the external environment, it will cause the expression of a ribonuclease MazF and the bacteria will die.
In the process of glyphosate degradation, formaldehyde will be produced. Formaldehyde promoter will be activated when the concentration of formaldehyde at high level, and the activity is positively correlated with the concentration of formaldehyde. When constructed with inverter, the function of the formaldehyde promoter will be reversed. So, when the intracellular concentration of formaldehyde is at low level, it will trigger the expression of ribonuclease MazF to kill the bacterium.
Since our products contains genetically modified organisms in the lab, even inside a "containing" device. Before we put our devices into production, testing and application beyond the lab, extensive testing should be performed to ensure whether our engineered bacteria is definitely safe for humans and the environment.
Besides, China passed a new biosecurity law and it would come into effect on April 15, 2021. The law would establish systems for biosecurity risk prevention and control, including risk monitoring and early warning, risk investigation and assessment, and information sharing. It would also have provisions to prevent and respond to specific biosecurity risks, including major emerging infectious diseases, epidemic and sudden outbreaks, and biotechnology research, development and application. To keep our activities legal, applying for the permits and approvals is necessary if we execute our proposed implementation.
Xiamen University, Fujian, China
No.422, Siming South Road, Fujian, P.R.China 361005
