CONICET | Buscador de Institutos y Recursos Humanos

A Scheffersomyces (Pichia) stipitis NRRL Y-7124 clone adapted in acid hydrolysate of jojoba lignocellulosic residues by an adaptive evolution strategy increased up to 4-fold its viability and up to 8-fold its vitality values, compared to its isogenic parental strain, after challenging it with non-related physico-chemical stresses that the yeast could face during an industrial bioprocess of cellulosic ethanol production e.g.: ethanol, oxidative stress, osmotic shock, thermal shock and phenolic acid. All stresses assayed increased intracellular reactive oxygen species (ROS) concentration in both strains, yet remained lower in the adapted clone. After ethanol stress ROS levels reached values up to almost 15-fold higher in the isogenic parental strain and adapted clone. Activity of the antioxidative enzymes catalase and superoxide dismutase accompanied intracellular ROS level variations after exposition of cell populations to stresses, being their increase more pronounced in the adapted clone than in the parental strain, with up to 7-fold higher concentration after ethanol stress. Glycogen and trehalose intracellular concentrations increased significantly more in the adapted clone than in the parental strain after stress exposure, reaching values 2 and 5-fold higher than control for trehalose in the adapted clone for ethanol and osmotic stress, respectively. The adapted clone exhibited a significantly higher efficiency of bioethanol production in anon-supplemented non-detoxified hydrolysate of jojoba cake, with a yield of 60.5 % of the theoretical maximum (vs. 43.8 % for the parental strain). The results suggest that robustness of an industrial yeast is associated to its oxidative stress tolerance, and that trehalose contributes to its resistance to specific stresses.