Science Buddies: "Ask an Expert"

Hello,
I am trying to do a science fair project on the effects of nanoparticles on algae growth and biofuel production. I had a few doubts and concerns on my methods of growing the algae. I'm most likely going to use a species high in lipid content, such as B.braunii or Chlorella sp..

1. Since I am doing biofuel production, should I grow the algae in petri dishes and spread nanoparticles on top of them, or should I grow the algae in a bioreactor (which I can make from water bottles) and add the nanoparticles to the water?

2. Would it be okay to use colloidal dispersions of nanoparticles for my project?

Thank you for your time.

Kriti

Hi Kriti,

Sorry to take so long getting back to you. In order to answer your questions, I need to ask you some first.

• What is your hypothesis?
• What nanoparticles are you planning to use?
• Are you adding something to the nanoparticles?

I am assuming that since you are measuring the production by the algae of lipids that can be used as fuel, you are going to do something to the algae to make them either grow faster or produce more lipid or both. The standard illuminated, air-bubbled bioreactor would be your best choice, I think, because it is used by most researchers.

The nanoparticles we use in the lab are made of a chitin derivative known as Chitosan and they are about the size of a large molecule, 100 nanometers. They are very good for carrying proteins, nucleic acids and drugs into animal cells because they are about 1/200 the diameter of the cell. I don’t know how well they would work for an alga such as Chlorella that has a cell wall.

In answer to your question—yes, a colloidal suspension of nanoparticles is fine to use. One thing you have to be careful of, however, is clumping together of the particles—aggregation. Chitosan has a net positive charge at pH 7 so the particles repel each other. You should do some research on your particles to make sure they don’t aggregate when you add them to the algae culture.

Are you planning to test a range of concentrations of nanoparticles? That is the usual way to measure an effect. Post more details of your procedure and we will be able to give you better advice on the experiments.

Best wishes,

Sybee