Team:NTHU Taiwan/FertilizerTank

Fertilizer Tank

Overview

Ever since the drip irrigation system was invented, the precise controlling of agricultural watering can be achieved. However, optimizing the usage of fertilizer has rarely been applied. After some heavy research, we noticed that nutrition absorption of certain types of plants is highly dependent on the surrounding temperatures. As a result, we designed the Fertilizer Tank to host our engineered bacterium, which can then be integrated into the modern drip irrigation system to enhance the efficiency of water and fertilizer absorption.

Figure 1. Three-view diagram of Fertilizer Tank
Figure 2. Fertilizer Tank
Figure 3. Fertilizer Tank Workflow

Structure

In order to achieve waterproofing and easy-manufacturing, we used a 3D Printer with PLA filament owing to its low cost while also being water-resistant.

Figure 4. Structure Construction

Filter


Introduction

The filter is the most crucial part of our fertilizer tank. These filters have to take care of both the biosafety concerns and separate the products of each chamber. The two chambers in our design are the fatty acid chamber (FA chamber) and fertilizer conversion chamber (FC chamber). Depending on the function of each chamber, the properties of polymer membrane differ, but all membranes are equipped with small pores (diameter<10μm) for biosafety purposes. More details are on Human/Collaborations page.

Figure 5. FA chamber
Figure 6. FC chamber

FA chamber filter

In the FA chamber, lipid in agar reacts with lipase and breaks into fatty acid. The rate of which is dominated by the temperature-sensitive activity of lipase; then the fatty acid will be released into the FC chamber through the FA chamber filter. The hydrophilic property of the FA chamber filter enables fatty acid to pass through but blocks the lipid at the same time, so that the main reactant, lipid, is conserved in the upper chamber for long-time, stable production of fatty acid.


This hydrophilic membrane is offered to us by Prof. Ying-Ling Liu [1] and consist of poly-benzoxazine (figure1). Originally, this material should be hydrophobic due to rich hydrogen bonds, so the water and polar molecules are seized by the membrane. However, after the basic solution treatment (immersing in pH 9 solution for 5 minutes), poly-benzoxazine will be deprotonated and the polarity decreases sharply. Thus, fatty acid can flow through the membrane.


Figure 6. Polybenzoxaine and intermolecular bonding
Figure 7. Hydrophilic membrane from Y-L,Liu labr

FC chamber filter

The FC chamber contains the E.coli coded with the fatty-acid-induced promoter and UreABC. Combining with the amount of fatty acid generated in the upper chamber, the E.coli has a corresponding rate of transcription and synthesizing ammonium. In other words, the FC chamber can produce the exact amount of nutrients that the targeted plants need.



Experiments & Results

Thanks to the help from NCTU_Formosa, we got the raw data of filtration efficiency, and these data are further analyzed here.


  • Filtration Efficiency

    Figure 8. Membrane performance in different level height

    According to Figure 8, we reach three conclusions:

    1. Half of the culture can be filtered within 40 minutes, which is somewhat longer than the time our lipase and TTSS E.coli are designed to fully react and induce.
    2. As the level height is dropping, the efficiency of filtration (tangent line of the graph) also declines. At the height of 3 cm, there is barely any filtrate flowing down.
    3. The stuck culture might slightly change the fatty acid concentration in the next reaction cycle.
    Figure 9. Filtration efficiency changing over time

    Compared with our fatty-acid-sensing model, the fatty-acid-induced promoter needs to have a sufficient amount of product in 10 minutes, but it takes 40 minutes for the solution to filter through the membrane! That is, this membrane is not efficient enough to keep up with our production rate. However, it is the fixed dimension that is lowering the filtration efficiency. If we redesign the tank shape to become thinner and higher, the excessive height may exert enough pressure on the membrane, thus increasing the filtration rate.



Water Valve

According to our model, the LipaseA protein will have 10 minutes to complete its reaction of producing fatty acid from agar, so we added two water valves to control when the product is released into the downstream irrigation pipes.

References

  1. Ching-Ting Liua and Ying-Ling Liu, pH-Induced switches of the oil and water selectivity of crosslinked polymeric membranes for gravity-driven oil-water separation, Journal of Materials Chemistry A, 2016
  2. Bart De Gusseme et.al, Virus disinfection in water by biogenic silver immobilized in polyvinylidene fluoride membranes, Water Research, 2011

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