Novel Method for Polysaccharide Synthesis Using an Enzyme: The First in Vitro Synthesis of Cellulose via a Nonbiosynthetic Path Utilizing Cellulase as Catalyst

The in vitro synthesis of cellulose via a nonbiosynthetic path has been achieved for the first time by condensation of β-D-cellobiosyl fluoride as substrate for cellulase, a hydrolysis enzyme of cellulose, in a mixed solvent of acetonitrile/acetate buffer (pH 5, 5:1). The water-insoluble part of the products is “synthetic cellulose”, the structure of which was confirmed by comparison with an authentic natural cellulose sample with use of solid C NMR and IR spectroscopies as well as with a hydrolysis experiment. The present synthetic cellulose was converted to the corresponding triacetate whose molecular weight was at least 6.3 × 10³ (degree of polymerization (DP) ≥ 22). X-ray as well as 13C NMR analyses showed that its crystal structure is of type II with high crystallinity. Under reaction conditions of a higher substrate concentration or higher acetonitrile concentration, water-soluble cellooligosaccharides (DP ≤ 8) were produced predominantly.