PhD Comp Exam, Microbially Induced Calcium Carbonate Precip as a Biomineral Adhesive, Sobia Anjum
- Thursday, March 12, 2020 from 9:00am to 10:00am
- Roberts Hall, 102 - view map
Adhesives are liquid or semi‐solid materials used to bond two separate surfaces through chemical bonds, physicochemical attractions and physical interlinking. Most of the adhesives currently available in the market started being used during the industrial revolution in the nineteenth century, when the adhesives industry began to move from natural adhesives such as beeswax, casein and tree pitches towards synthetic adhesives. These adhesives were based on petrochemicals, rubber, or phenolic resins, and often contained volatile organic compounds (VOCs).
The harmful effects of these adhesives on human health and the environment had not been studied in earnest until the 1980s. Furthermore, the petroleum dependency of hydrocarbon-based adhesives raised environmental concerns due to the non‐biodegradability of the adhesives.
These concerns led to a new interest in natural adhesives which are non‐toxic and environmentally safe. Several of these (albumin, casein, beeswax, gum arabic, soybean proteins, and starch) have remained in use for specialized applications. However, their use is limited because of their sensitivity to water and low mechanical strength compared to synthetic adhesives.
My work explores a natural composite adhesive, a biomineral adhesive, formed by ureolytically induced calcium carbonate precipitation (UICP). The ureolysis is carried out by the enzyme urease, which means that the biocomposite can be formed by free enzyme (EICP) as well as by microbial cells containing that enzyme (MICP).
Preliminary work shows that bacterially induced biomineral composite can withstand shear forces up to 12,000 psi, which is comparable to the shear strength of high‐performance structural adhesives. The enzymatically induced biocomposite showed comparatively lower shear strength than bacterially induced composite, however, its strength can be improved by using higher concentrations of enzyme. EICP formed composites can be used in applications where the presence of living bacterial cells is undesirable.
- Department of Chemical and Biological Engineering