  This is a Comment to the paper by Sharma and Chamon in Phys. Rev. Lett. 87
(2001) 096401 (cond-mat/0011025). We show that the prediction of the universal
charge pumped per cycle in the fast limit for attractive electron-electron
interaction is invalid. We also prove the quantization of the pumped charge for
repulsive interaction in the limit of adiabatic pumping.
