Acetylation of desacetyl glutaryl 7-aminocephalosporanic acid (7ACA), an intermediate in the two-stage enzymatic cleavage of cephalosporin C, has been accomplished in aqueous media with acetic anhydride. Because the reaction is done in water, conversion of desacetyl glutaryl 7ACA to glutaryl 7ACA can be accomplished at an early stage in the purification process. Evidence is presented that desacetyl cephalosporin C in cephalosporin C broth is formed from the mycelial catalyzed hydrolysis of cephalosporin C.