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Team:IIT Delhi/Project
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- ✔ In today’s modern world, greenhouse gases such as NOx and SOx pose a major global issue that needs to be addressed. These oxides also increase the oxidizing capacity of the atmosphere which are responsible for the photochemical production of ozone in the lower layers of the atmosphere which has detrimental effects. Sulfur Oxides (SOx, SO2) are the main precursors of air pollution which is a deteriorating problem as well. Producing acid rain and acidified soils, Sulfur Oxides not only result in respiratory problems such as asthma and pneumonia, but also destroy farm crops, buildings and environment, causing loss of millions of dollars every year.
- ✔ Both these gases also have detrimental effects on the environment and the iGEM Team IITD 2014 plans to combat this catastrophic effect by reducing the amount of the NOx and SOx gases ejected through the exhaust vents. We are in the process of engineering nrfA gene (that codes for nitrate reductase) in E.Coli to convert NOx to NH3 (Clarke et al;2008) and for SOx reduction we will incorporate cys1(sulfite reductase) that converts SO2 to H2S (Growth Yields and Growth Rates of. Desulfovibrio vulgaris (Marburg) Growing on Hydrogen plus Sulfate and Hydrogen plus Thiosulfate as the Sole Energy Sources, Arch. Microbiol. 117, 209-214 [1978]) and sqr (sulfide quinone reductase) to convert H2S to S. In order to realize whole sulfur metabolism pathway, we use several bioinformatics web sites such as KEGG and NCBI. We anticipate that the use of genetically engineered bacterium would subside the efficiency of existing chemical methods.
- ✔ Genetic engineering of E.Coli for Nitric Oxide (NOx) and Sulfur Oxides (SOx, SO2 ) reduction.
- • Engineer a plasmid that will express the nitrite reductase enzyme (nrfA) under a constitutive promoter for high rate of expression. The nrfA gene will be cloned from E.coli K12 strain. E. coli with the engineered plasmid would express NrfA which would convert the NOx to ammonia.
- • Engineer a plasmid that would express the Sulfite reductase (CysI or Dsr) and Sulfide-Quinone reductase (Sqr) under a constitutive promoter. CystI and Dsr will be cloned from Pseudomonas Aeruginosa and Desulfovibrio Desulfuricans respectively. Sqr will be cloned from Synechococcus (SP. PCC 7942). Sulfite reductase converts SO-2 to H2S and sulfide-quinone reductase convert H2S to S.
- • To test the working of the engineered bacteria for the reduction of the NOx and SOx gases.
- ✔ Designing a prototype for the reduction of NOx and SOx from the exhaust gases.
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The prototype will have the following components:
- • A small Heat Exchanger
- • Bioreactor
- • A medium tank
- (a) Engineering the E.coli
- ● NOx removal:We will tackle the nitric oxide produced during the combustion processes by using the nitrite reductase enzyme NrfA of E. coli. Our idea is to engineer a plasmid that will express the nitrite reductase enzyme NrfA under the control of a constitutive promoter so that the promoter is active independent of transcription factors, and is "on" by default. NrfA will be expressed in excess and will convert the NO to ammonia.
- ● SOx removal: Sulfur Oxides (SOx, SO2) are the main precursors of air pollution which is a serious problem now a days. Apart from producing acid rain and acidified soils, Sulfur Oxides also cause breathing problems such as asthma, pneumonia and destroy farm crops, buildings and environment as well, causing millions in loss each year. Our plan is to genetically engineer E.coli by cloning CysI gene into E.coli and use this bacteria to remove SO2 from our environment. Also, this bacteria produces H2S, which is a substrate for Sulfide-Quinone Reductase (sqr). This H2S will get converted to Sulphur.
- (b) Designing tabletop model- The prototype will have the following components
- 1.A small Heat Exchanger:Since the temperature of the exhaust gases would be very high for our engineered bacterium to work, we have decided to use an heat exchanger for reducing the temp of the exhaust gases.
- 2. Bioreactor: It is the most important part of the design where the reduction of the harmful gases takes places. The genetically engineered E.Coli will be immobilized in the bioreactor and responsible for all the reduction of gases inside the reactor. The gases will be passed from the bottom and the medium will be sprayed at a very slow rate from the top of the reactor. The immobilization material will be a polymeric material with a positive zeta potential. The prototype design will be a proof of the concept, which can undergo various changes on the basis of the requirements of the industry. The concept of reduction of harmful gases using genetically engineered bacteria can be used in automobiles, thermal power stations and various other industries. The size of the device needs to be manipulated according to the industrial requirement.
- 3. A medium tank: This will include a solution having all the nutritional requirement of the bacteria. Thus it will contain a minimal medium required by the bacteria for its growth.
