  Using mean field theory, we have studied Bose-Fermi mixtures in a
one-dimensional optical lattice in the case of an attractive boson-fermion
interaction. We consider that the fermions are in the degenerate regime and
that the laser intensities are such that quantum coherence across the
condensate is ensured. We discuss the effect of the optical lattice on the
critical rotational frequency for vortex line creation in the Bose-Einstein
condensate, as well as how it affects the stability of the boson-fermion
mixture. A reduction of the critical frequency for nucleating a vortex is
observed as the strength of the applied laser is increased. The onset of
instability of the mixture occurs for a sizeably lower number of fermions in
the presence of a deep optical lattice.
