Project Director

Barbosa, Jose

Department Examiner

Giles, David K.; Kovach, Margaret


Dept. of Biological and Environmental Sciences


University of Tennessee at Chattanooga

Place of Publication

Chattanooga (Tenn.)


Saccharomyces cerevisiae is a microorganism that is commonly used in industries, but its productivity is significantly hindered by its inability to resist high stress levels found in industrial processes. By increasing stress tolerance in S. cerevisiae, its role in industrial processes could be maximized. The objective of this study is to determine if complementation of lipocalin genes into the wildtype and knockout strains of S. cerevisiae can increase stress tolerance against a variety of stressors. We identified the knockout yeast strains, ALD3, ALD4, PDX3, and ILV1, as being sensitive to various stressors including salinity, heat, oxidative, and osmotic stresses. Arabidopsis thaliana At-TIL (AT5G58070) and Homo sapiens OBP2B (AY358981), two identified lipocalin genes, were cloned into the yeast shuttle vector, p415 GPD, and transformed into the wildtype, BY4743, and knockout strains of yeast. Growth phenotypes of both transformants and non-transformant cells of the wild type and knockout strains were tested against heat, oxidative, and osmotic stresses, in addition to their alcohol tolerance levels. Compared to the wildtype and knockout strains, ALD4::TIL showed increased stress tolerance against heat when exposed to 50°C for 10 minutes. BY4743::TIL and ALD4::TIL showed increased stress tolerance against oxidative stress when exposed to 1mM H2O2 , but none of the transformants showed increased tolerance when exposed to 2mM H2O2. The cells showed no improvement in osmotic stress tolerance with either of the lipocalins, At-TIL or OBP2B, when exposed to 1.0M sorbitol. The ALD4::TIL and ILV1::TIL transformants showed increased stress tolerance against salinity when exposed to 0.8 M NaCl, while the OBP2B transformants seem to be irresponsive to the salinity stress.


First, I would like to thank Dr. Jose Barbosa for supporting me throughout this project and being a wonderful mentor. I want to thank Dr. David Giles and Dr. Margaret Kovach for serving on my committee. I would also like to thank William Komtchenko, Catarina Felgueira, and Thomas Galbato for their previous work related to this study. This work has been supported by the UTC Department of Biology, Geology, and Environmental Science and by funding from the Office of Undergraduate Research and Creative Endeavor (SEARCH Award) and the Beta Beta Beta Research Foundation.


B. S.; An honors thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Bachelor of Science.




Saccharomyces cerevisiae -- Effect of stress on; Yeast


At-TIL; lipocalin; OBP2B; stress tolerance; yeast


Microbial Physiology

Document Type



[ii], 31 leaves