polysaccharides esterified products, compositions containing ketene dimer product of ring opening of beta-lactone and processes for preparing them.

A process for preparing an esterified polysaccharide comprising adding an effective amount of enzyme to a reaction mixture of polysaccharide, wherein said effective amount of enzyme is 0 01 to 10% by weight based on the weight of the mixture reaction of polysaccharide, and said reaction mixture comprises a reaction medium, a polysaccharide and a ketene dimer.