To study the role of Hal5 protein kinase on ethanol tolerance in saccharomyces cerevisiae

Abstract

Saccharomyces cerevisiae is one of the simplest eukaryotic model organism to study various parameters of ethanol tolerance. It has attracted a huge consideration for the cost-conscious and environmental friendly bioethanol production by the fermentation of sugars. Since the elevated concentration of ethanol and other inhibitors produced during the pretreatment of lignocellulosic biomass has deleterious consequences on the growth, viability and eventually on fermentation performance. The interruption of cellular ion homeostasis affects membrane permeability and reduced metabolic activity. Thereby certain cations play an important role in neutralizing physiological stress caused by higher ethanol concentration, as well as increased concentration of lignocellulosic-derived inhibitors like acetic acid and vanillin. Since K+ ion plays a prominent role in maintaining ion homeostasis and in other vital physiological progressions in the yeast cell. In the present study, we tried to evaluate the role of Hal5p; a protein kinase that up-regulates potassium uptake by activating the Trk1-Trk2 potassium transporters concerning ethanol stress in yeast. Therefore understanding the interplay between ion homeostasis and cell survival under different stressful conditions seems to have desirable for economical ethanol production. Our findings suggested that Hal5p protein kinase overexpression improves the robustness of yeast strains against various stressful conditions, including high concentration of ethanol, toxic cations, lignocellulosic biomass inhibitors and low pH. The increased tolerance of Hal5 overexpressed strain is attributed to the accumulation of trehalose and glycogen, which play a vital role in maintaining cellular integrity and enhancing stress tolerance. Moreover, the overexpression of Hal5 contributes to the maintenance of cellular redox balance and reduction of oxidative damage under ethanol stress, as evidenced by lower ROS production, lipid peroxidation, protein carbonylation, and higher GSH/GSSG ratio.