AbstractContinuous deacetylation of cephalosporin C, 7‐aminocephalosporanic acid, and of 2‐methoxyethyl acetate in packed beds of an immobilized esterase is described by simple empirical equations relating conversion to space velocity and temperature. The choice of process conditions is discussed in relation to the effects of temperature on column efficiency, column life, growth of microbial contaminants, and the rates of thermal decomposition of the substrates. At the preferred temperature of 10°C columns were operated continuously for one month with only small losses in efficiency.