Congo red works fine for detecting CMCase activity. I never heard of Grams iodine, which seems more appropriate to detect amylase activity. You could also use methylumbelliferyl-beta-D cellobioside, as CMC-Congo red will only detect endoglucanases
Grams`s iodine (2.0 g KI and 1.0 g iodine in 300 mL distilled water)is recommended as it can enhance the sharpness of the clearance zone and for fast results. for details plz see the attached paper
Thanks Ahmad for the suggestion..I went through that paper but still there is an confusion about Grams iodine with Amylase positive or cellulase positive microbes..?
You still need to use CMC as susbtrate for screening of cellulases producing strain. Grams iodine only for colouring agent as replacement of congo red to increase the sharpness for hydrolysis zone..