Difference between revisions of "Team:Hong Kong-CUHK/Description"

ABCDE (AzotoBacter vinelandii in Carbon Dioxide to methane Energy)

Objective

In this project, we aim to utilize modified nitrogenase in Azotobacter vinelandii to convert carbon dioxide (CO₂) to methane (CH₄). It is hoped to produce a fuel while fixing carbon.

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 convert CO₂ into CH₄ inside the bacteria Azotobacter vinelandii. A. vinelandii is a facultative aerobe 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, storage of CH₄ is cheaper than that of H₂ due to a lower boiling point from the perspective of fuel storage. 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, and being a potent greenhouse gas. 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) enhancing H₂ recycling to return its energy back to the reaction chain, and; (2) increasing intracellular CO₂ concentration.

MNOPQ (Magnetic Nanoparticles On Particular reQuirement)

Objective

We aim to produce magnetic nanoparticles to meet certain requirements. Azotobacter vinelandii is also used in this project because it provides an intracellular anaerobic condition that is essential for the production processes.

Background and Significance

Magnetosome is an organelle with magnetic iron crystal (magnetite) encapsulated by lipid bilayer which is originated from bacteria such as Magnetospirillum gryphiswaldense. It serves as a navigational device in magnetotactic bacteria by interacting with the Earth magnetic field. Magnetic beads formed could be applied in various aspects. Biomolecules, such as enzymes and antibodies, can be expressed on the magnetosome so that they can be easily controlled by magnet for specific purposes.

Unfortunately, most of the magnetotactic bacteria require microaerobic conditions for magnetosome biogenesis, which is hard to maintain with normal lab equipment. We are transferring essential genes for magnetosome formation into A. vinelandii, a facultative aerobe with an intracellular anaerobic environment, in hope of producing magnetic beads with functional biomolecules under aerobic conditions with greater yield. We are also modifying the transmembrane protein presented on magnetosome membrane by fusing with biomolecules. Reactions could be more accelerated as magnetites generated from magnetosome provides a greater surface area-to-volume ratio than that of artificial magnetic beads.

Applications

One of the applications is to use engineered magnetites to capture heavy metal ion in water. Heavy metal is one of the major components in marine pollution. Different kinds of heavy metal ions, such as Pb, Cu and Ni, are found in marine system. By expressing different heavy metal binding proteins onto magnetic beads, heavy metal ions could be captured and be easily removed by magnet. It is better than the previous methods, in terms of operating cost, efficiency and eco-friendliness.

We are also adding antibodies on magnetosome for immunoprecipitation. Due to the smaller size of magnetosome than traditional magnetic beads, magnetosome with antibodies could have a higher binding efficiency. Also, the antibodies containing magnetic beads can be massively produced in bacteria.