Silica gel-encapsulated AtzA biocatalyst for atrazine biodegradation

• Published in: Applied microbiology and biotechnology 2012-10, Vol.96 (1), p.231-240
• Main Authors: Reátegui, Eduardo, Reynolds, Erik, Kasinkas, Lisa, Aggarwal, Amit, Sadowsky, Michael J., Aksan, Alptekin, Wackett, Lawrence P.
• Format: Article
• Language: English
• Subjects: Activated carbon; Adsorption; Analysis; Atrazine; Atrazine - metabolism; Biocatalysts; Biodegradation; Biomedical and Life Sciences; Biotechnology; Biotransformation; Curing; Degradation; Drinking water; Drug Carriers - metabolism; E coli; Encapsulation; Environmental Biotechnology; Enzymatic activity; Enzymes; Enzymes - chemistry; Enzymes - genetics; Enzymes - metabolism; Enzymes - ultrastructure; Escherichia coli; Escherichia coli - chemistry; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli - ultrastructure; Gene expression; Genetic recombination; Herbicides; Laboratories; Life Sciences; Lipids; Metabolic Engineering; Microbial Genetics and Genomics; Microbiology; Microscopy, Electron; Nanoparticles; Polyethylene glycol; Polymers; Porous materials; Potassium; Recombinant; Rigidity; Silica; Silica Gel - metabolism; Silicon dioxide; Soil contamination; Spectroscopy, Fourier Transform Infrared; Studies; Temperature; Water Pollutants, Chemical - metabolism; Water treatment; Water treatment plants
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-011-3821-2

Encapsulation of recombinant Escherichia coli cells expressing a biocatalyst has the potential to produce stable, long-lasting enzyme activity that can be used for numerous applications. The current study describes the use of this technology with recombinant E. coli cells expressing the atrazine-dechlorinating enzyme AtzA in a silica/polymer porous gel. This novel recombinant enzyme-based method utilizes both adsorption and degradation to remove atrazine from water. A combination of silica nanoparticles (Ludox TM40), alkoxides, and an organic polymer was used to synthesize a porous gel. Gel curing temperatures of 23 or 45 °C were used either to maintain cell viability or to render the cells non-viable, respectively. The enzymatic activity of the encapsulated viable and non-viable cells was high and extremely stable over the time period analyzed. At room temperature, the encapsulated non-viable cells maintained a specific activity between (0.44 ± 0.06) μmol/g/min and (0.66 ± 0.12) μmol/g/min for up to 4 months, comparing well with free, viable cell-specific activities (0.61 ± 0.04 μmol/g/min). Gels cured at 45 °C had excellent structural rigidity and contained few viable cells, making these gels potentially compatible with water treatment facility applications. When encapsulated, non-viable cells were assayed at 4 °C, the activity increased threefold over free cells, potentially due to differences in lipid membranes as shown by FTIR spectroscopy and electron microscopy.