Enhancement of Stress Tolerance and Ethanol Production in Saccharomyces cerevisiae by Heterologous Expression of a Trehalose Biosynthetic Gene from Streptomyces albus

Abstract

Since yeast is often exposed to a number of environmental stresses including high ethanol concentration and temperature, the ability to grow and produce ethanol under such stressful conditions is an important factor in industrial bioethanol production. Trehalose is found in many organisms including Saccharomyces cerevisiae, and has been known to play an important role in enhancing various types of stress tolerance. In this study, Streptomyces albus trehalose-6-phosphate synthase gene (salC) was expressed in Saccharomyces cerevisiae, and the recombinant strain with salC gene showed significantly improved stress resistances and ethanol production. The stress sensitivity and viability tests indicated that the recombinant had a greater resistance to ethanol than the control. The results of flask cultures at an elevated temperature showed that the expression of salC played a good role of protecting cells from the heat stress. The recombinant strain was found to consume 100 g/L glucose and produce 39 g/L ethanol at 40 °C with an ethanol yield 6 % higher than that of the control strain. In the fed-batch experiment in a bioreactor to investigate ethanol production capability of the recombinant strain under a high-ethanol stress condition as in the industrial practice, it produced 69 g/L ethanol with about 18% higher yield and about 13% higher productivity than the control strain.