Pesch, K. L.; Simmert, U. (1929). "Combined assays for lactose and galactose by enzymatic reactions". Milchw. Forsch 8: 551.

Try to use Resazurin... so much articles have the method.

This is a very complex problem. For good advice you will need to provide us with a lot more information.

For starters, I recommend looking at the following review:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3911769/

Also, you may want to look for other papers by Dr. Ischiropoulos:

https://www.researchgate.net/profile/Harry_Ischiropoulos/

Thank you a lot for your advices, I may read them before I start this work. Again, thank you for your help.