Minimal Position of Branching Random Walks in Random Environment

We consider branching random walks in random environment (BRWRE) on ℕ with only one particle starting at the origin. Particles reproduce according to offspring distribution (which depends on its locations) and move one step to the right (with a probability in (0,1] which may depend on the location) or stay in the same site. We give an estimate to the minimal displacement of BRWRE at time n in the case where the essential supremum of mean number of offsprings which stay in the same place is equal to 1.