We investigate the spectral properties of buoyancy-driven bubbly flows. Using high-resolution numerical simulations and phenomenology of homogeneous turbulence, we identify the relevant energy transfer mechanisms. We find (a) at a high enough Galilei number (ratio of the buoyancy to viscous forces) the velocity power spectrum shows the Kolmogorov scaling with a power-law exponent -5/3 for the range of scales between the bubble diameter and the dissipation scale (η). (b) For scales smaller than η, the physics of pseudo-turbulence is recovered.