CONTROLLED GLUCOSE metabolism IN YEAST USING A TRANSISTOR‐LIKE DEVICE
Student: Zhenlu Song
Professor: Siu‐Tung Yau
09/04/2014
Introduction
 This study demonstrates the use of a transistor‐like device to regulate the kinetics of glucose metabolism at an electrode containing immobilized yeast.
 The rate of glucose metabolism and the rate of ethanol and ATP production were controlled by applying the gating voltage of the device at an insulated gating electrode.
 The study also involved observation of a correlation between glucose metabolism and ethanol production
 The result are as follow. Method The method used for conducting this study involved the following main steps:
 Yeast preparation
 Preparation and operation of electrode and electrochemical measurement system
 Measurement of glucose : BREEZE® 2 blood glucose meter
 Measurement of ATP : BacTiter‐Glo™ Microbial Cell Viability Assay
 Measurement of ethanol : Ebulliometer(Dujardin‐Salleron, Paris, France)
 Scanning electron microscopy Method
1) Cyclic voltammetric
measurement of glucose oxidation
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The system shown in figure 1 was used to carry out cyclic voltametry under the following conditions:
I.
Presence of phosphate buffered saline(PBS)
II. Glucose added to PBS
III. Positive VG
IV.
Bare electrode with and without glucose in the solution.
 Fig.1. Modified three‐electrode electrochemical cell (Song, Y, J Wang, and ST Yau)
Method
2) VG‐dependent glucose metabolism
 The system in figure 1 was used to monitor the change in glucose concentration under different values of VG. This was done for all the conditions mentioned in 1 above. 3) VG‐dependent production of metabolic end‐products.
Changes in the amount of ATP were measured through Luminescence assay of ATP in yeast cells while ethanol production was monitored through ebullliometry of glucose processed electrochemically. Results
 Cyclic voltammetric measurement of glucose oxidation
 VG‐dependent glucose metabolism
 VG‐dependent production of metabolic end‐
products
Results
ATP is synthesized in the three processes. In
cells, ATP is produced following the overall simplified reaction
under the aerobic condition: Glucose 1 oxygen 1 specific sequence
of reactions controlled enzymes & coenzymes ——. Carbon dioxide 1 water 1 ATP.
In Figure.2.
Figure.2. Overall reaction of anaerobic metabolism
Results Of Cyclic Voltammetric Measurement Of Glucose Oxidation
Fig.3. CVs showing the yeast‐induced oxidation of glucose with the arrows showing the redox peaks of yeast (Song, Y, J Wang, and ST Yau).
Results Of Vg‐dependent Glucose metabolism Fig.4a. VG‐Dependent change in glucose concentration under aerobic condition (Song, Y, J Wang, and ST Yau).
Fig.4b. VG‐Dependent change in glucose concentration under aerobic condition (Song, Y, J Wang, and ST Yau).
Results of VG‐dependent production of metabolic end‐products
Fig.5a. simultaneous measurements of VG‐controlled glucose metabolism and ATP production (Song, Y, J Wang, and ST Yau).
Fig.5b. simultaneous measurements of VG‐controlled glucose metabolism and ethanol production (Song, Y, J Wang, and ST Yau).
Summary of Results
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Glucose oxidation occurs at the yeast‐immobilized electrode
VG can be used to control oxidation
There was no change in the concentration of glucose in the control experiment.
The glucose concentration in the sample decreased as the amount of ATP increased.
The amounts of glucose and ATP changed inversely with time even in the absence of VG The rate of glucose metabolism and ethanol production increased as positive VG was applied and vice versa.
Glucose metabolism rate was reduced when rotenone was used.