  We discuss localized ground states of Bose-Einstein condensates in optical
lattices with attractive and repulsive three-body interactions in the framework
of a quintic nonlinear Schr\"odinger equation which extends the
Gross-Pitaevskii equation to the one dimensional case. We use both a
variational method and a self-consistent approach to show the existence of
unstable localized excitations which are similar to Townes solitons of the
cubic nonlinear Schr\"odinger equation in two dimensions. These solutions are
shown to be located in the forbidden zones of the band structure, very close to
the band edges, separating decaying states from stable localized ones
(gap-solitons) fully characterizing their delocalizing transition. In this
context usual gap solitons appear as a mechanism for arresting collapse in low
dimensional BEC in optical lattices with attractive real three-body
interaction. The influence of the imaginary part of the three-body interaction,
leading to dissipative effects on gap solitons and the effect of atoms feeding
from the thermal cloud are also discussed. These results may be of interest for
both BEC in atomic chip and Tonks-Girardeau gas in optical lattices.
