Anomaly-free chiral fermion sets and gauge coupling unification

In this work we search for minimal sets of chiral fermions, with arbitrary quantum numbers, beyond the Standard Model that are anomaly-free and lead to vector-like particles under SU (3) and U(1)(em) after symmetry breaking. We further study which of these anomaly-free sets lead to unification of the gauge couplings at energy scales higher that 5.0 x 10(15) GeV in order to be consistent with proton decay bounds. A similar study is performed in the context of the SU(5) gauge group; for some of the anomaly-free sets found it is possible to obtain unification of the gauge couplings with the extra fermions decoupling at high intermediate scales.