Cellulose is not dissolve in water due to its chemical structure (long straight chain) and it has a high degree of polymerization (DP=10000-15000). Cellulose has a β(1→4) linked D-glucose units while starch has a alfa(1→4) linked D-glucose. Therefore, starch is dissolve in water while cellulose is not dissolve.
Cellulose is not dissolved in water. But what if you still want to use cellulose then cellulose derivatives may one of the option. You can look for some cellulose derivatives such as CMC, HPMC ... or any other alternative.
You should not need to "dissolve" your cellulose in water to accomplish formation of CMC. It is an alkaline reaction in water - cellulose fibers are hydrated, not dissolved. Here is a link to a research paper that may help you accomplish your objective.