The effect of plasma treatment of polyester (PET) fabric with respect to nisin adsorption and antibacterial activity was studied. Both cleaned untreated PET fabric and plasma-treated PET fabric were separately dipped in aqueous nisaplin solution with 0.5 and 1% of nisin, for 24 h under stirring, and then dried. With 1% of nisin, high and immediate antibacterial activity against Staphylococcus aureus was observed, and this activity was maintained even after 24 h. However, with 0.5% of nisin, no immediate bacterial reduction was observed, and only the untreated PET fabric exhibited antibacterial activity after 24 h. Only nisin molecules which can diffuse from the fabric can impart antibacterial activity, as demonstrated by the absence of bacterial inhibition zone after complete removal of releasable nisin in water. The desorption capacity of nisin from the fabric into water was monitored by tensiometry, while the presence of residual strongly sorbed nisin on the fabric was confirmed by wettability, zeta potential measurements, and wash durability test after nisin coloration by a protein dye. Plasma treatment, which increases the hydrophilic behavior of the PET fabric (WCA reduced from 80 degrees to 42 degrees), increases considerably the quantities of strongly and weakly sorbed nisin. However, it does not improve antibacterial activity compared to the PET fabric without plasma treatment. The reduced mobility of the nisin molecules due to chemisorption of the first layers of nisin on the plasma treated PET fabric can explain the reduced antibacterial activity with 0.5% nisin. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 129: 866-873, 2013