Team:Hong Kong-CUHK/Description

ABCDE(AzotoBacter vinelandii in Carbon Dioxide to methane Energy)

Objective

This project utilize modified nitrogenase in Azotobacter vinelandii to convert carbon dioxide(CO2) to methane(CH4).

Background and Significance

With the exploitation of carbon based fossil fuels, we sought for an alternative solution to combat the global energy crisis by utilizing a gas pollutant – CO2 through carbon fixation. To maintain current living standard, alternative energy sources are unprecedentedly demanding. We are now engineering a bacteria Azotobacter vinelandii to econvert CO2 into CH4 inside the bacteria Azotobacter vinelandii. A.vinelandii is a facultative areobe with an intracellular anaerobic environment which is essential for the reduction reactions.

Why CH4

CH4 produced can serve as a fuel and any CO2 produced during the process can be returned to the system to CH4 generation. Comparing to hydrogen(H2), a popular alternative energy source, because of its "cleanliness after combustion, from the perspective of fuel storage, storage of CH4 is cheaper than that of H2 due to a lower boiling point. Thus it requires less energy to liquefy. Our engineered bacteria would also be able to convert the greenhouse gas CO2 into CH4 in closed systems, which eliminates the disadvantage of using CH4 as a fuel. Additionally, no change needed to be made on current car engines, which are designed to use of hydrocarbon fuels.

Goal to be achieved

From literatures, we found out that the carbon fixation process is not efficient enough, as most energy is wasted in H2 production. Therefore, we are tackling the fixation efficiency through two approaches: (1) the enhancing H2 reaction chain, and (2) increasing intracellular CO2 concentration.


MNOPQ(Magnetic Nanoparticles on Particular Requirement)

Main idea

This project’s main idea is to produce nanoparticles with magnetic properties under certain requirement. Azotobacter vinelandii is used again because these bacteria can provide an intracellular anaerobic condition, which is needed for making the nanoparticles.

Significance
The magnetosome is a magnetic nanoparticle with size 30nm to 120nm which is a magnetite surrounded by magnetosome membrane (MM). It is originated from the magnetotactic bacteria called magnetospirllum gryphiswadense. Magnetosome serve as a navigational device in magnetotactic bacteria by interaction with magnetic field of the Earth.

Biomolecules, such as enzyme, antibody, can be immobilized on the magnetosome in some ways, so that biomolecules can be easily controlled by magnet. One way to immobilize biomolecules is genetically modifying the transmembrane protein on MM into protein-biomolecules fused protein. As the size of magnetosome much smaller that the size of artificial magnetic beads magnetosome has a greater surface area to volume ratio; more biomolecules can be immobilized.

Application

One application of our project is using magnetosome in removing heavy metal ion in water. In China, water pollution is serious. 1.6 million tons of e-wastes per year are produced in China since 1990s. Different kinds of heavy metal ions such as Pb, Cu, Ni…etc, are found in the marine system, with lead being one of the major metals in e-waste recycling sites. The exposure of lead could have negative impact on brain development. By using magnetosome and immobilizeing different heavy metal binding proteins onto it, different kinds of heavy metal ions can be immobilized and be easily removed from the water by magnet. This novel method is better than the previous recent methods, regarding the operating cost, efficiency and eco-friendliness. It keeps the water in high quality for large demand in population.

The second application is adding antibodies on magnetosome for immunoprecipitation. Due to the smaller size of magnetosome than traditional magnetic beads, magnetosome with antibodies probably have a higher binding efficiency. Also, the antibodies added magnetosome can be mass-produced in bacteria.