[artery]

Hi everyone,

I'm trying to measure the concentration of cellulose in a sample. I know phenol-sulphuric acid assay is used for measuring common carbohydrates, but I'm not sure if the method will work for cellulose too. Hopefully I can find some comments here.

Thanks.

[Furanone]

I have not used Phenol-Sulfuric Acid method on cellulose ever, but many times on starches and various food hydrocolloids (eg. xanthan, carrageenan, guar, etc.), and it has worked for all these (although there may be slight differences in the standard curve slope from a typical glucose standard curve). I would think as long as your cellulose is dissolved (eg. Cadoxen, LiCl/DMAC), the method should work, since it is an incredibly sensitive method so the amount of solvent (cadoxen, LiCl/DMAC) would be very slight compared to what you are adding with the mostly sulfuric acid and phenol solution. If the cellulose is not fully dissolved in a suitable solvent, I would worry about underestimating your results.

[Furanone]

I forgot to ask -- What other components are in your sample matrix other than cellulose? If you go to the original article for the Phenol-Sulfuric Acid Method (Dubois et al., 1956), there is an absorbance for proteins as well, but it is about 1/10 (10%) that for carbohydrates, so there could be some potential sources of error.

[artery]

I forgot to ask -- What other components are in your sample matrix other than cellulose? If you go to the original article for the Phenol-Sulfuric Acid Method (Dubois et al., 1956), there is an absorbance for proteins as well, but it is about 1/10 (10%) that for carbohydrates, so there could be some potential sources of error.

I'm trying to figure if an insect is able to digest cellulose. As I'm sampling the faecal material, there is probably some proteins even if I omit them in the diet. Is it possible to normalise the concentration of cellulose from Phenol-Sulfuric Acid assay with concentration of protein determined by Bradford protein assay in a sample?

Right, I have not thought of the part about dissolving the cellulose. Thanks!

[Furanone]

Yes, faecal matter as your matrix might be a complex sample to measure. I'm not sure in insect feces but in human feces, bacteria mostly e. coli make up approx. 33% by weight of the feces and this will be high in proteins. Correction factors can always be used, but it is best if you know everything that is in the sample.

Another possibility is to use a cellulase activity assay as this would be much more specific for testing for cellulose. I did a quick search online and found that for testing for cellulose digestion by insects, carboxymethylcellulose (CMC) is often used as it is highly soluble in water unlike unmodified cellulose. This would also allow you to filter out or centrifuge most of the insoluble faecal matter (ie. bacteria) to have a cleaner sample to analyze.

Here are links I found:
http://deepblue.lib.umich.edu/bitstream/handle/2027.42/25406/0000855.pdf?sequence=1
http://www.nrel.gov/biomass/pdfs/42628.pdf
http://www.worthington-biochem.com/cel/assay.html