Overproduction of Glutathione by Applying Stress, Cysteine Addition, and Fed-Batch Mode on Fermentation of Saccharomyces cerevisiae
<p align="justify"> <br /> <br /> The Industrial interest of glutathione (GSH), as a pure substance or accumulated in yeast, has been prominent as a result of various applications of GSH in food and pharmaceutical industries. Studies to enhance GSH content inside yeast ce...
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| Format: | Final Project |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/29553 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | <p align="justify"> <br />
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The Industrial interest of glutathione (GSH), as a pure substance or accumulated in yeast, has been prominent as a result of various applications of GSH in food and pharmaceutical industries. Studies to enhance GSH content inside yeast cells have been limited to non-genetic ways since target-engineered strains are barely acceptable in food industries. In the following work, therefore, stress conditions, cysteine addition coupled with high cell density fed-batch fermentations of Saccharomyces cerevisiae R58 for GSH accumulation have been investigated. Stress conditions applied on this study included temperature shift from 30 to 50°C and 27°C, pH shift from 5 to 1.2 and 8.8, and osmotic stress by addition of 80 g/l NaCl solution. Another strategy was to add cysteine as one of GSH precursors into the fermentation broth. Lastly, fed-batch fermentation to achieve high cell densities was also studied. <br />
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Osmotic stress appeared as the best result amongst stress variations applied in this work, resulting in an increase of intracellular GSH content from 0.848% to 1.284%-w/w as well as GSH yield on glucose from 0.0011 (control) to 0.0023 g GSH/ g glucose. Cysteine addition alone improved GSH content up to 0.984%-w/w as well as yield on glucose from 0.0011 to 0.0080 g GSH/g glucose. Fed-batch fermentation elevated cell concentration from 10.73 (control) to 12.72 g dried cell weight (DCW)/l along with an increased final intracellular GSH content of 0.912%-w/w. Combined cysteine addition with fed-batch fermentation enhanced overall GSH production and reached 1.695%-w/w of final GSH content and stood out as the best strategy in this study. <br />
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