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The Biomicrofluidics of Microbiologically Induced Calcite Precipitation Mediated by Sporosarcina pasteurii
- Author / Creator
I studied a particular bacterium Sporosarcina pasteurii (S. Pasteurii) which has a unique ability to cause chemical precipitation in an aqueous medium in the presence of certain molecules like urea. These precipitated chemicals can go deep inside a network of micro-scale pores and cause clogging. As a result, the porous matrix may gain significantly in terms of structural and mechanical strength.
The clogging of pores has wide-ranging implications in areas spanning from heritage structure remediation to carbon sequestration. These reasons have led to a significant increase in interest in S. Pasteurii and the mechanism behind the induction of precipitation, especially inside porous media with a characteristic pore size of the order of microns.
I prepared cultures of S. Pasteurii which were subsequently enriched through a recipe of external additives. These chemicals, through a complex chain of reactions, lead to the formation of calcium carbonate. The role of S. Pasteurii comes from the fact that it secretes large volumes of extracellular urease which acts as a catalyst, thus accelerating the reaction kinetics. This phenomenon, in its entirety, is often called Microbiologically Induced Calcite Precipitation (MICP).
For the present work, I have analyzed MICP from various physical, chemical and biological angles. Firstly, a new protocol of culturing the bacterium and enriching it suitably thereafter has been developed. This provides us with a reliable tool to accelerate in situ precipitation and study the temporal evolution of the system.
Secondly, a semi-solid platform to observe the movement of bacteria inside a micro-porous medium and measure their speeds has been developed. Based on experiments on this platform, I have studied the spatial location of nucleation sites for crystals; the interplay between flagellar and diffusive motilities, as well as the role of cell membranes in inducing precipitation.
Finally, a mechanistic analysis has also been undertaken to quantify the enhancement in mechanical strength and structural properties, such as porosity and permeability of the representative porous medium. A full range of mechanical tests and chemical characterization have been performed to understand the effects of MICP on bulk and surface properties of the system.
- Graduation date
- Spring 2018
- Type of Item
- Doctor of Philosophy
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