Jesreal L. Arcillas, Angelo M. Jamerla, Leo Albert G. Sala (February 2006)
Philippine Science High School Western Visayas Campus – Department of Science and Technology (DOST-PSHS WVC), Brgy. Bito-on, Jaro, Iloilo City 5000, Philippines
ABSTRACT
Studies have shown that some bacteria are capable of producing voltage as they metabolize certain organic substances.
This study aimed to measure the voltage output generated by E. coli when fed with various molar concentrations of glucose (0.5, 1, 1.5, and 2) and various percent by volume concentrations of ethanol (10%, 20%, 30%, and 40%) at different periods of consumption. It also determined and compared the rate of change in the voltage output generated by E. coli with respect to time using glucose and ethanol.
It was hypothesized that the rates of change of voltage outputs generated when E. coli is fed with different glucose and ethanol concentrations do not differ significantly. the concentration of glucose and ethanol and the duration of metabolism are not good predictors of voltage output.
A galvanic cell was used to generate voltage with potassium ferricyanide at the cathode chamber and glucose- or ethanol-fed E. coli culture in the anode chamber. Voltage output was measured using a voltmeter from 0 to 24 hours.
Two molar glucose and 20% ethanol recorded the highest voltage output, both generated after 24 hours of consumption.
Positive rates of change with respect to time were found when E. coli is fed with ethanol and with 0.5M and 2M glucose. Negative rates of change were found when E. coli is fed 1M and 1.5M glucose.
The rate of change is significantly higher when E. coli is fed with 20% ethanol (a=0.05).
Multiple regression analysis revealed that concentration of glucose and ethanol and the duration of consumption of glucose are not good predictors of voltage output. However, the duration of consumption of ethanol is a good predictor of voltage output.