Science Buddies: "Ask an Expert"

I am measuring the ability of the fungus Phanerochaete chrysosporium to degrade lignin in newspaper. For 30 days, I have been incubating 9 5g samples of shredded newspaper, 6 of which I inoculated with samples of the fungus and added malt extract to and 35 mL of water to. Now I need to measure the lignin content of my control (no fungus) and experimental, but am having trouble finding a reliable and feasible method. I looked into the Acid Detergent Lignin process, but could not find specifics on how to perform the procedures. I need something that is quick, as science fair is approaching. I have access to a basic high school chemistry lab. Any help or references would be much appreciated. Thanks!

Hi dustdances10,

I just wanted to let you know we are trying to find an Expert to answer your question (your question is very specific so it is taking longer than normal to find an expert knowledgeable in this area). Some of us experts have tried doing a search using Google to find something that would fit your needs, but we weren't able to find anything that could be done in a high school lab. We'll post back here if we are able to solve your problem.

Update: I was able to find something about this acid procedure, read this and see if it is helpful: http://books.google.com/books?id=uLzdv8 ... in&f=false

Measuring lignin is difficult at best in arbitrary samples, see http://crop.scijournals.org/cgi/content/full/45/3/832
Ignoring the difficulties of insuring a reproducible lignin yield, see http://jds.fass.org/cgi/reprint/71/11/2976.pdf
This and similar methods require spectrogrphic analysis. Do you have access to a spectrograph in your chemistry lab? If not, then you might want to think about other kinds of measurements.

Tensile strength of the paper samples is certainly something easy to measure. If lignin in your treated samples has been reduced, then the internal cellulose structure will be structurally compromised. How uniform this change is will depend on how uniform the initial colonization of the organisms were on the test sample.

Thanks for your quick reply! I ended up starting my procedure prior to reading, but this info will be helpful anyway. I had read the Crop SciJournals article but had not found the other two.
I ended up soaking each 5g newspaper sample in 70mL of 0.5 M sulfuric acid. They have been soaking for 10 hours at the temperature (21 celsius) suggested in one article I read. I'm going to rinse the samples and strain them with distilled water, but then I am not sure how to proceed. I was planning to simply dry the samples then weigh them and be finished. However, many studies use the Klason method (mentioned in one paper you sent me) which involves a second soaking in a more concentrated acid solution. Do you think that would be necessary? Since I'm following the exact same procedure for all the samples (control and experimental) would it matter whether I follow a founded method from professional studies?

Hi,

In science, we often follow established procedures. While it doesn't really help with our own data (as you say, you have treated the control and experimental samples in exactly the same way), it helps us to compare our data to data in other studies. I'm sure you can imagine what would happen if we all used slightly different methods and got different results!

In this case, however, it's up to you. You can always dry and weigh it and then put it through another round of soaking. I also don't know whether or not you have access to the more concentrated acid (I'm sure you know this, but be sure to use proper safety equipment/procedures, especially when working with concentrated acid!). It also depends on how much time you have for the experiment. My advice would be to soak it twice if you can, but if you can't, I think it's fine for a science fair.