Hi Marcelo

The affinity of one beta glucosidase to X substrate not necessarily the same of another one thus you need to test several substrates in order to find the best for yours, here I add esculin (very cheap substrate), you can tell by naked eye that there is beta glucosidase activity or not.

Hope this helps   

There's a lot of substrates for beta-glucosidades. Some of them are synthetics and usually have higher enzymatic activity them the natural ones, like 4-Nitrophenyl β-D-glucopyranoside, 4-Nitrophenyl β-D-fucopyranoside (and variations changing the carbohydrate). Those substrates release an yellow color when cleaved, and can be easily analised through spectrophotometry (abs around 320nm).

If you need it more sensible, you can use like 4-Methylumbelliferyl β-D-glucopyranoside (again, can vary the carbohydrate) and read it through fluorimetry.

But, if you want to use a natural substrate, use cellobiose and make dosage of reducing sugar using DNS ou any kit that measures glycose. (dont forget to divide by 2, cause it produces 2 glycoses for each cleavage)

hope it helps.