  We study the s-wave I=2 \pi \Sigma and I=1 KN interactions from 2+1 flavor
full lattice QCD simulation for relatively heavy quark mass corresponding to
m_{\pi}=700 MeV. The s-wave meson-baryon potentials are obtained from the
Nambu-Bethe-Salpeter amplitudes. Potentials in both channels reveal short range
repulsions, which suggest the importance of the Pauli blocking effect. The I=1
KN scattering phase shifts are calculated and compared with the existing
experimental data.
