The rotary drum bioreactor, having moderate surface area to volume ratio compared with other bioreactor types, can provide adequate oxygen mass transfer with less power consumption and shear stress compared with STB. For plant cell cultures, the rotary drum bioreactor has shown advantages in terms of suspension homogeneity, low shear environment and reduced wall growth, over either air-lift or STB (Sajc et al., 2000). However, the limitation is their comparatively high energy consumption in large scale operations and difficulty in scale-up.