2024 AIChE Annual Meeting
Chitosan-Based Hydrogel Beads for Encapsulation of Bacteria for Bioremediation of Chloride Solvents
Chlorinated compounds, such as 1,1,1-trichloroethane (TCE) and 1,4-dioxane, are found in many groundwater aquifers that supply drinking water to the US. TCE was used commonly in the dry cleaning of clothes and degreasing of engines on many Air Force bases. These contaminants are linked to causing long-term health complications in humans. Although remediation techniques like pump and treat exist, such methods are simply not effective enough to manage the spread of these compounds. These contaminants can be broken down by bacteria through a process called cometabolism. Rhodococcus rhodochrous ATCC 21198 is a bacterium capable of degrading these specific chlorinated compounds. A community of bacteria can be created by immobilizing them inside of hydrogel beads. The ultimate goal is to place the beads into a perforated column in a groundwater aquifer for passive bioremediation. However, the beads will be stacked on top of each other and must withstand the weight of the bead pack. Based on the chitosan coating techniques of Sarma et al., our research examines if chitosan-coated sodium alginate beads would be stronger than sodium alginate beads alone, or if stronger hydrogel beads could be made by using only chitosan. The chitosan beads also needed to be tested to determine if they are habitable for the bacteria.
Therefore, the engineering objectives of the research project were:
(1) Develop a method to increase the modulus (stiffness) of current sodium alginate
beads using a chitosan coating.
(2) Develop a method to produce chitosan beads with a higher modulus (stiffness) than
sodium alginate beads.
(3) Immobilize ATCC 21198 bacterium in chitosan beads and test for their viability,
since chitosan is known to have antimicrobial properties.
These trials showed that not only is chitosan weaker than sodium alginate, it is also not a viable method of bacteria immobilization. This could be attributable to the more acidic pH from the addition of glacial acetic acid, and the antimicrobial properties of the chitosan used in the beads.