Applied Microbiology and Biotechnology

, Volume 96, Issue 1, pp 231–240 | Cite as

Silica gel-encapsulated AtzA biocatalyst for atrazine biodegradation

  • Eduardo Reátegui
  • Erik Reynolds
  • Lisa Kasinkas
  • Amit Aggarwal
  • Michael J. Sadowsky
  • Alptekin Aksan
  • Lawrence P. Wackett
Environmental biotechnology


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.


Atrazine Silica Bacteria Biodegradation AtzA E. coli 



We thank Mr. Baris Mutlu for his help in conducting experiments. This research was supported by a National Science Foundation grant (CBET-0644784) to AA, a research grant from Syngenta Crop Protection to LW, MS, and AA, and a seed grant to AA and LW from the BioTechnology Institute at University of Minnesota.

Supplementary material

253_2011_3821_MOESM1_ESM.doc (74 kb)
ESM 1 (DOC 74 kb)


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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Eduardo Reátegui
    • 1
  • Erik Reynolds
    • 4
  • Lisa Kasinkas
    • 1
  • Amit Aggarwal
    • 3
  • Michael J. Sadowsky
    • 4
    • 5
  • Alptekin Aksan
    • 1
    • 4
  • Lawrence P. Wackett
    • 2
    • 4
  1. 1.Biostabilization Laboratory, Department of Mechanical EngineeringUniversity of MinnesotaMinneapolisUSA
  2. 2.Department of Biochemistry, Molecular Biology and BiophysicsUniversity of MinnesotaMinneapolisUSA
  3. 3.Department of Bioproducts and Biosystems EngineeringUniversity of MinnesotaSaint PaulUSA
  4. 4.BioTechnology InstituteUniversity of MinnesotaSaint PaulUSA
  5. 5.Department of Soil, Water, and ClimateUniversity of MinnesotaSaint PaulUSA

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