<P>A cross-linked mutant endoglucanase II was prepared for enzymatic polymerization to cellulose. The cross-linked enzyme is composed of three mutant enzymes showing polymerization activity. A characteristic feature of the polymerization with this cross-linked enzyme is formation of cellulose fibrils in contrast to plate-like crystals obtained by using a free enzyme.</P> <P>Graphic Abstract</P><P>Cross-linked mutant EGII<SUB>core2H</SUB> which has at least six catalytic core domains catalyzes the synthesis of fibrous cellulose by enzymatic polymerization.<BR><IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1cc14202j'><BR></P>