Experiments were performed to study the effects of multiple draft tubes with perforated plates on average gas holdup, phi, volumetric mass transfer coefficient, k(L)a, and liquid mixing time, t(M), in a bubble column with 5 draft tubes, and a varying number of holes, n, of constant diameter on the perforated plates. phi and k(L)a increased with increasing superficial gas velocity u(Go), and n, respectively. The highest values were obtained for 5 draft tubes with perforated plates having n=323. t(M) decreased with increasing u(Go). For the perforated plates with n = 21, t(M) increased with increasing N at the same u(Go); but with n=323, t(M) was independent of N and became equal to one with no draft tube.