Industrial application of encapsulated bacteria for biodegradation of hydrocarbons in water requires mechanically stable materials. A silica gel encapsulation method was optimized for Pseudomonas sp. NCIB 9816-4, a bacterium that degrades more than 100 aromatic hydrocarbons. The design process focused on three aspects: (i) mechanical property enhancement; (ii) gel cytocompatibility; and (iii) reduction of the diffusion barrier in the gel. Mechanical testing indicated that the compressive strength at failure (σf) and elastic modulus (E) changed linearly with the amount of silicon alkoxide used in the gel composition. Measurement of naphthalene biodegradation by encapsulated cells indicated that the gel maintained cytocompatibility at lower levels of alkoxide. However, significant loss in activity was observed due to methanol formation during hydrolysis at high alkoxide concentrations, as measured by FTIR spectroscopy. The silica gel with the highest amount of alkoxide (without toxicity from methanol) had a biodegradation rate of 285±42nmol/L-s, σf=652±88kPa, and E=15.8±2.0MPa. Biodegradation was sustained for 1 month before it dropped below 20% of the initial rate. In order to improve the diffusion through the gel, polyvinyl alcohol (PVA) was used as a porogen and resulted in a 48±19% enhancement in biodegradation, but it impacted the mechanical properties negatively. This is the first report studying how the silica composition affects biodegradation of naphthalene by Pseudomonas sp. NCIB 9816-4 and establishes a foundation for future studies of aromatic hydrocarbon biodegradation for industrial application.
Bibliographical noteFunding Information:
Contract grant sponsor: National Science Foundation (NSF) Contract grant sponsor: University of Minnesota (UMN) Institute on the Environment (IonE) Contract grant sponsor: UMN Office of the Vice President for Research (OVPR) Contract grant sponsor: UMN BioTechnology Institute (BTI) Contract grant sponsor: UMN Undergraduate Research Opportunity (UROP)
© 2016 Wiley Periodicals, Inc.
- Aromatic hydrocarbons
- Mechanical properties
- Pseudomonas sp. NCIB 9816-4
- Silica gel