Yes, this does seem implausible. Have you checked your DNS reaction against a range of glucose concentrations, to generate a calibration curve? This is important for double-checking your process and making sure it is quantitative. 

Dear Leigh Aldous,

Thank you for your response. Yes, we have checked it against several calibration curves as well as various dilution series and we are getting the same result. A colleague mentioned that reducing sugar is a tricky quantification technique given the functional groups that can affect the ultimate mass. I was hoping to get more info on this.

1 g of 100% pure and dry cellulose should only give 1.11 g/g glucose (extra 0.11 g in weight from the H and OH added during hydrolysis), so it is possible you are getting 100% glucose out (plus a bit error to bring it up to 1.15 g).

But if your feedstock is not 100% pure and dry cellulose, then it could possibly be due to an interference, e.g. Discoloured solution that is affecting your colorimetric measurement. If this is not the case, you are measuring how many equivalents of DNS is converted, and converting this to mass using glucose equivalents. If the molecular weight of your reducing molecules are less than that of glucose, then you end up with an overly large mass.

If you care about what's in there, likely you will have to set up a HPLC process to investigate. If you only care about glucose then you will need a glucose-selective quantification method. For example, a colorimetric process using glucose oxidase. Many conventional blood-glucose meters will work well in a buffered solution, and typically selectively quantify glucose between 2 and 10 mM (but not every model works selectively or works quantitatively in an enzymatic broth, so a calibration curve would be required). 

Dear Profs Leigh Aldous and Solange Mussatto,

Thank you for your invaluable input with this question. Your answers have been most helpful!