  We present a simple derivation of the 'Dirac' equation for the supermembrane
fermionic field in a D=11 supergravity background with fluxes by using a
complete but gauge-fixed description of the supergravity-supermembrane
interacting system previously developed. We also discuss the contributions
linear in the supermembrane fermions -the Goldstone fields for the local
supersymmetry spontaneously broken by the superbrane- to the field equations of
the supergravity-supermembrane interacting system. The approach could also be
applied to more complicated dynamical systems such as those involving the
M5-brane and the D=10 Dirichlet branes.
