Methods for breaking yeast cells and the stability of the glucose tolerance factor extract from yeast

• Main Authors: Min-Yu Chung, 鍾閔伃
• Other Authors: Guo-Jane Tsai
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/23935660577742902361

碩士 === 國立臺灣海洋大學 === 食品科學系 === 95 === A protein from Saccharomyces cerevisiae No.1 has been demonstrated to have the activity of glucose tolerance factor (GTF) that can enhance the glucose uptake rate of adipose cells. The aims of this research are to investigate the pH and temperature stability of the GTF extract using the differentiated 3T3-L1 cell assay model, and to investigate the efficacy of breaking methods for this yeast cells. The GTF extract is quite stable between pH 2-pH 9. The residual activities of this GTF extract after being heated at 45 ℃, 55 ℃ and 65 ℃ for 2 h are 96 %, 79 % and 35 %, respectively. Its thermal inactivation constants at 65 ℃, 75 ℃ and 85 ℃ are 8.8 x 103, 1.13 x 104, and 1.27 x 104 min-1, respectively. To reserve the GTF activity, the optimal temperature and pH value for autolysis of S. cerevisiae No.1 cells are 45℃ and pH 6.0, respectively. During cell autolysis, the addition of ethyl acetate, ammonia, citric acid or lytic enzyme could increase the amino nitrogen content and the relative GTF activity in the supernatant, among which ethyl acetate at the concentration of 5 % being the most effective. The released amino nitrogen content and the relative GTF activity were increased from 107 mmole/mL and 41 %, respectively, for the control, to 325 mmol/mL and 121 %, respectively, for 5 % ethyl acetate addition. When both 5 % ethyl acetate and protease 1 were added during cell autolysis the released amino nitrogen content could be increased 513 mmol/mL. However, the relative GTF in the supernatant were 101 %. which was less then that for 5 % ethyl acetate added along. By scanning electron microscopic observation the phenomenon of cell plasmolysis was found for cells treated with various chemical tested, while collapsed cells were monitored for cells treated with various enzymes tested.