The situation of water resources
The life activities of all creatures in the universe cannot be separated from water resources. Water resources are indispensable and play an important role in human development. However, humanity is now facing the problem of water pollution.
Chinese total water resources rank fourth in the world, but the per capita water resources possession is only about 1/4 of the world average level. Increasing water pollution has made the availability of fresh water resources scarce. Therefore, the pollution of water resources is a major problem facing today's society.
The damage of sewage
Water pollution not only causes the waste of water resources but also has a great impact on human health and economic development. In China, each step up in sewage discharge standards increases treatment costs by 0.3 to 0.5 CYN per ton on average. With the development of the economy, the discharge of sewage is increasing year by year and the pressure of sewage treatment is getting bigger and bigger.
The importance of sewage treatment
The sewage treatment project is an extremely important link to the environmental treatment problem. It is of great significance to the development of human beings to enhance the modernization and intelligence of sewage treatment and improve the capacity and quality of sewage treatment.
The pollutants contained in sewage are mainly composed of various chemical pollutants, physical debris and harmful viruses, bacteria and other microorganisms.
Sewage treatment can be divided into physical, chemical and biological methods.
Physical methods are usually used for sewage with large water capacity, strong self-purification capacity and low requirement of sewage treatment degree because of their simplicity and economy.
The chemical method is the use of chemical reactions to treat toxic and harmful substances in wastewater, commonly used are the chemical precipitation method, photocatalytic oxidation method, ion exchange method, etc.
Although the physicochemical method and chemical treatment technology can reduce water pollution to a certain extent, they will cause secondary pollution to the environment.
The
biological method
uses the metabolic function of dissolved or colloidal microorganisms to decompose and oxidize organic matter in sewage into stable inorganic matter to achieve the purpose of sewage purification. The commonly used methods include the activated sludge method and the biofilm method. The biological method is
environmentally sustainable
and has
strong adaptability and volume load
.
Overview
Our project aims to transform 168 strains of
Bacillus subtilis
using synthetic biology. And then we plan to construct a molecular switch in
Bacillus subtilis
to express a large number of enzymes related to nitrogen oxidation under blue light irradiation to control the total nitrogen content in water in order to decompose nitrogen-containing organic matter and avoid eutrophication of water. The suicide mechanism is activated under green light irradiation, which make the strain die and reduce the cost of biosafety treatment.
Design1
signaling pathway diagram
Design2
Mechanism diagram
We have designed the
supporting hardware
and
software facilities
. In order to restore the sewage water information more truly, we take the water temperature, light intensity, dissolved oxygen, nitrogen salt concentration and other indicators in the ecological tank as the research objects.
We use
biosensors
to sense the environmental information in the ecological tank which can combine with 3D modeling technology. They comprehensively improve the overall safety, intelligence, reliability and aesthetics of the ecological tank.
Advantages
These devices can systematically and intelligently detect the content of various indicators in the ecological tank, display relevant data on the screen in real-time and feedback to users.
They can provide lighting conditions to regulate the life activities of
Bacillus subtilis
, and indirectly control whether to release bacteria according to the water conditions.
The importance of sewage treatment
After a series of literature research and the study of excellent team wiki studies, we planned and discussed our experimental design. Finally, we chose "Blue-green light-regulated sewage treatment bacterium preparation based on
Bacillus subtilis
" as our official competition topic.
Why we choose Bacillus subtilis ?
Bacillus subtilis
is a commonly used model strain which has the ability to treat sewage and a relatively mature and thorough research system and it is convenient for synthetic biology transformation.
Our design
We designed the blue light regulatory pathway mediated by EL222 photosensitive protein and the green light regulatory pathway mediated by CcaR/CcaS system to construct a blue-green light-regulated molecular switch. The engineered strain carried with
amo
(for coding ammonia monooxygenase) ),
hao
(for coding hydroxylamine oxidase), and
nirS
(for coding nirite reductase) was expressed under blue light irradiation, which could significantly reduced the total nitrogen and nitrogen in the water.
Green light
nucA
(for coding NucA, which is an extracellular enzynem that can hydrolyze nucleic aicd) is expressed when exposed to green light. It can cause the strain to kill itself which confirm the biosafety. We selected the high copy plasmid pUC19 as the vector of
el222
and
nucA.
A series of engineered plasmids were constructed for optical regulatory network construction. At the same time, the green fluorescent protein gene was used as a reporter gene, and the fluorescence intensity was observed under the fluorescence microscope to reflect the expression of the target gene, and the results were tested.
What we need to overcome?
Biological wastewater treatment is a large and complex system. There will be a lot of uncertainties in the treatment process due to the special process of sewage treatment, microbial biochemical reactions involved in the process. It is difficult to model the whole control process since that many variables are involved and the changes are complex.
Our solutions
Since aquatic life is the first to be affected by water pollution, we plan to use an ecological tank as a simulation reactor in this project. The ecological tank is easier to control the reaction conditions of wastewater simulation and has a lower cost. In addition, the water quality is relatively clear, and the transmittance to light is high.
It has a mature light system and water index detection system, which is convenient for light regulation-related experiments and water index modeling analysis. This series of advantages will be more helpful to our early research on sewage treatment.
Our aims
Our hardware design is mainly for the convenience of the experimental part can have a relatively stable experimental environment to ensure that the experiment is not affected by or less by external factors, more accurate to get our expected experimental results.
Details
Outline
The shape of the ecological cylinder is mainly shaped by 3D modeling and 3D printing. The wiring and chip position is fully considered in the design so that the space of the ecological cylinder is fully utilized and the shape is beautiful.
Modular sensors
We designed corresponding modular sensors according to common indicators of sewage treatment (ammonia nitrogen, total nitrogen, pH value, temperature) and uploaded the monitored data to the cloud platform in real-time for users to download.
The light intensity switching system
We designed corresponding modular sensors according to common indicators of sewage treatment (ammonia nitrogen, total nitrogen, pH value, temperature) and uploaded the monitored data to the cloud platform in real-time for users to download.
In bioinformatical modeling, we have predicted the structures of four enzyme molecules and optimized them to be closer to their natural conformations. Then the stability of each region of enzyme molecule was evaluated and the unstable regions in enzyme molecule were analyzed. In addition, we predicted the region of the enzyme active center of each enzyme molecule by molecular docking, which provided reference information for the structural design and optimization of the four enzyme molecules.
In mathematical modeling, we use Matlab and Simbiology to predict the biological growth curve and simulate the denitrification reaction to better help the experimental group to carry out their experiments and help our project to achieve better progress and success.
Theoretically speaking, our bacterial preparation can effectively reduce the nitrogen content of water and avoid eutrophication of water and achieve the purpose of purifying water quality. It can be widely used
in industrial and domestic wastewater, fish farm water, aquarium water and other different water bodies to reduce the nitrogen content.
According to the characteristics of accurate light regulation and environmental protection, our bacterial preparation can be used for the protection of endangered species living environment water bodies,especially oceanariums, aquariums, etc. It can provide strict physical and chemical conditions for their growth and reproduction as well as reduce the amount of water exchange. It can finally achieve the effect of maintaining the stability of the ecosystem to protect endangered animals.
