Silica gel-encapsulated AtzA biocatalyst for atrazine biodegradation.
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.
Biostabilization Laboratory, Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
Eduardo
E
Reátegui
Erik
E
Reynolds
Lisa
L
Kasinkas
Amit
A
Aggarwal
Michael J
MJ
Sadowsky
Alptekin
A
Aksan
Lawrence P
LP
Wackett
D001280:Atrazine / Q000378:metabolism*; D001711:Biotransformation; D004337:Drug Carriers / Q000378:metabolism; D004798:Enzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D060847:Metabolic Engineering; D008854:Microscopy, Electron; D058428:Silica Gel / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000378:metabolism
D004337:Drug Carriers; D004798:Enzymes; D014874:Water Pollutants, Chemical; D058428:Silica Gel; D001280:Atrazine