Several phenomenological and cosmological aspects of a minimal extension of the Georgi-Glashow model, where the Higgs sector is composed by 5_H, 15_H, and 24_H, are studied. It is shown that the constraints coming from the unification of gauge interactions up to two-loop level predict light scalar leptoquarks. In this GUT scenario, the upper bound on the total proton decay lifetime is tau_p < 1.4 x 10^36 years. The possibility to explain the matter-antimatter asymmetry in the universe through

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... e decays of SU(2)_L scalar triplets is also studied. We find that a successful triplet seesaw leptogenesis implies an upper bound on the scalar leptoquark mass, M_Phib < 10^6-7 GeV. We conclude that this GUT scenario can be tested at the next generation of proton decay experiments and future colliders through the production of scalar leptoquarks.