Science Buddies: "Ask an Expert"

Hello!

I am an 8th grade student working in the area of biofuels, specifically cellulosic ethanol. I was working on a project with mentors at Penn State, when unforeseen circumstances required us to halt the experiment. I am now rushing to find a new project in the same area, as my science fair experimentation portion is due at the beginning of February. I have a specific project that I could possibly try, as an extension of "Turn Plants into Biofuel with the Power of Enzymes" as seen on science buddies. I would like to take a enzyme that breaks down cellulose(a type of cellulase) and combine it with different ratios of an enzyme that breaks down hemicellulose(a type of hemicellulase) to see which ratio works the best. I have a few questions about this. Which type of plant would be best to use in this process, meaning it would contain high levels of cellulose and hemicellulose or would I be able to use only the sugar substrate provided in the Enzyme kit? How would I use these enzymes to break down cellulose/hemicellulose? How would I measure the amount of glucose produced? And finally, do you have any other project in the biofuels field that I could complete by February? I'm really sorry for all of these questions. Any help would be greatly appreciated. Thank you!

Hi Arya,

Sorry to hear that your experiments could not be continued at Penn State. It’s a really interesting and timely project you picked. As I understand it, cellulosic ethanol production is being developed so that biofuel can be made from any plant material to spare crops like corn from overuse as fuel. Since all plants contain cellulose, it would be possible to use a great variety of plant material as a feed stock for ethanol production.

Did you have some particular plants in mind to test for cellulosic ethanol prodcution? I have heard of a plant called switchgrass that is being tested for making biofuel http://www.scientificamerican.com/artic ... -than-corn

I would think that any type of grass could be used, but you said your question was how much cellulase relative to hemicellulase to use to get optimum sugar conversion. Enzymatic breakdown of cellulose produces glucose only but hemicellulose can be digested into xylose, arabinose, galactose and other sugars. Most yeast species can ferment glucose into ethanol, but I don’t know whether they can use these other sugars. Which yeast were you planning to use for ethanol production?

I don’t know the details of how to prepare the plant material for enzymatic digestion. This is something you would have to research online. I do think this is a really great project and you should get going on it right away. Do you have to buy the kit or can you just order the enzymes? You can get a glucose meter such as diabetics use at any pharmacy and I would think this would work for measuring glucose concentration after cellulase digestion of the plant material. I don’t know if you could measure the other sugars, however.

The second part of the project would be to show that the digested plant material can be fermented by yeast to produce ethanol. You can probably use bread yeast since that is a live culture, but brewer’s yeast would be better since your purpose is to make ethanol, not bread. Look for a store that sells supplies for brewing and wine making, or order a brewer’s yeast culture online.
The problem I see is how to measure the amount of ethanol produced by the yeast acting on the plant sugars. You’ll have to do some online reading to see if you can find a simple method. Yeast also produces carbon dioxide, so you could collect the CO2 during the fermentation and measure the amount produced. There should be a direct correspondence between ethanol and CO2 production.

I know you don’t have a lot of time to complete this project so let us know right away what you will try to do. I think it is a great experiment and I really want to know what happens when you digest the plant material with the different enzymes. If you could show increased yeast activity that would be fantastic!

Best wishes,

Sybee