Enhancement of stress tolerance and ethanol production in Saccharomyces cerevisiae by heterologous expression of a trehalose biosynthetic gene from Streptomyces albus

Abstract

The ability to grow and produce ethanol under 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. At elevated temperatures, the results of flask cultures showed that the expression of salC played a positive role in protecting cells from heat stress. The recombinant strain was found to consume 100 g/L glucose and to 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 the recombinant strain produced 69 g/L ethanol with about 16% higher yield and about 13% higher productivity than the control strain. This demonstrated the enhancement of ethanol production capabilities of the recombinant strain under a high-ethanol stress condition.