Cellulase is any of several enzymes produced chiefly by fungi, bacteria, and protozoans
that catalyze cellulolysis,
the decomposition of cellulose
and of some related polysaccharides;
specifically,
the hydrolysis of the 1,4-beta-D-glycosidic linkages in cellulose,
hemicellulose, lichenin,
and cereal beta-D-glucans.
Cellulases break down the cellulose molecule into monosaccharides ("simple sugars")
such as beta-glucose,
or shorter polysaccharides
and oligosaccharides.
The name is also used for any naturally
occurring mixture or complex of various
such enzymes,
that act serially or synergistically
to decompose cellulosic material