Masters Theses

Yingbo Guo

Date of Award

12-1991

Degree Type

Thesis

Degree Name

Master of Science

Major

Chemistry

Major Professor

J. Q. Chambers

Abstract

This research attempted to develop an effective method to detach a biofilm from a gold surface, so that repetitive measurements of the biomass can be made possible using a quartz crystal microbalance in an on-line configuration. This was an interdisciplinary effort involving both electrochemistry and microbiology.

The bacteria, Caulobacter crescentus, were used in the studies. They were allowed to grow in the growth media and to attach onto a gold surface. Both in situ and ex situ electrochemistry, including cyclic voltammetry (CV), controlled current and controlled potential electrolysis, were performed to detach the biofilm. According to an acridine orange direct counting technique using the fluorescence microscopy, continuous cyclic voltammetry during the growth period and ex situ electrolysis in 0.1 M NaOH solution after the growth period were found to effectively detach the biofilm. The surface population of bacteria generally decreased to 10% of the control. As low as 0.5% of the control population can be achieved. In situ CV, in situ electrolysis, and ex situ CV did not give consistent decrease of the surface population. Two mechanisms were proposed to account for these results.

It was concluded that, when combined with a quartz crystal microbalance in a suitable way, ex situ electrolysis in 0.1 M NaOH solution can detach the biofilm iv effectively, so that continuous measurements of the surface biomass and bacterial regrowth were possible.

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