Lignocellulosic wastes from agriculture are potentially useful as a low cost feedstock for production of bioethanol. During pretreatment of lignocellulosic materials, a wide range of inhibitory compounds to microorganisms are formed or released. The present work focused on production of bioethanol by Z. mobilis NRRL B-806 in different culture media. Inhibitory effects of the bio-products yielded in the pretreatment process of Eucalyptus globulus were determined. Results obtained showed that maximum bioethanol production yield YE/S for Z. mobilis NRRL B-806 was 87%. Ethanol production and glucose consumption were clearly affected by high inhibitors concentration present in pretreated liquors obtained by auto-hydrolysis.