In this work, the stabilizing effect of bovine serum albumin (BSA), peptone (PEP), and polyethylene glycol (PEG) during immobilization of Candida antarctica lipase on activated carbon was investigated. The influence of enzyme concentration and type of additive, added during the immobilization procedure, was studied using a 2 2 factorial central composite design. The goal was to maximize the synthetic activity of butyl butyrate, using butyric acid and butanol as substrate in n-heptane. An increase of 31-58% in the esterification activity was obtained when enzyme concentration on the supernatant was enhanced from 86.50 U m L -1 to 226.80 U mL -1 . An enhancement in esterification activity of 38-68.95% was observed, depending on the initial enzyme concentration, when PEP was used instead of BSA. No significant increase in the esterification activity was observed when PEP was replaced by PEG. However, thermal stability tests at 50°C showed that PEG had a higher stabilizing effect.