Bailey's method is the best.

[Bailey, M.J., Biely, P. and Poutanen, K. (1992) Interlaboratory testing of methods for assay of xylanase activity. J. Biotechnol. 23, 257-270.]

Prepare standard at 10 mu mole/ml conc.

DNSA is good for reducing sugars. 

Thanks. I went through that article. According to which Xylanase activity is expressed in terms of nkat. But most of the latest articles on xylanase have expressed it in terms of IU. So when you follow Bailey's method, whatever unknown you get from the curve is converted in IU ?

One unit of endo-xylanase activity was defined

as mu mols of xylose liberated per minute per ml of culture supernatant

[Subramaniyan, S., Prema, P., and Ramakrishna,

S. V., Isolation and screening for alkaline thermostable

xylanases, J. Basic Microbiol. 37, 431, 1997.]

I went through the article. One doubt I have.

When umol per minute is said , we have to devide by 10 (10 min was the reaction time in your article) ?

When umol per ml of supernatant is said do we have to multiply it by 5 , as 0.2 ml supernatant is used in the reaction mixture ?

Yes    X5 then  /10. 

eg. [x X5/10] X Dilution factor

ok thanks. And for running standard 4 different dilutions are taken. 1:1, 1:2, 1:3, 1:5 according to the protocol. What is the volume of standard solution used for assay ? 

Is it 2ml std + 3ml DNSA. boil 5 min. ?

Bailey's method has become the international standard for measuring xylanase activity.

In the past, I used the Nelson-Somogyi reducing sugars method, which appears to be more sensitive and can measure lower amounts of sugars than the Miller DNS method.