Conclusions  

1. The carboxylesterase isolated from A. viscosus NRRL B-1973 can esterify cello-oligomers and cellulose or de-esterify mono-, oligo-, and polysaccharides as well as small organic molecules such as isopropenyl acetate and triacetin.

 

2. The esterification is regioselective in that only positions O-2 and O-3, i.e. secondary hydroxyl groups are reactive, not O-6.

 

3. The enzyme maintains its activity in DMSO and acrylonitrile (up to 50% w/w) as well as in water.

 

4. The enzyme may be useful where surface esterification of polysaccharide nanocrystals is desired. This is particularly true where the substrate does not swell appreciably in water.

 

5. Further study will be required to fully characterize the action of the enzyme on a wider variety of substrates and the differing reactivity, if any, for different secondary hydroxyl groups.

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