Skip to main content

Long-term preservation of silica gel-encapsulated bacterial biocatalysts by desiccation


Whole cells encapsulated in silica gels are used in a wide variety of applications in biomedicine, biotechnology and bioremediation. Drying after encapsulation is desirable to enhance the strength of the gel and to make it lighter, facilitating its use, storage and transportation. However, preserving biological activity of the cells in a desiccated state remains a formidable challenge. In this study, different drying conditions for a silica gel-encapsulated bacterial biocatalyst (atrazine biodegrading Escherichia coli) were studied to enhance mechanical properties while sustaining long-term biocatalytic activity of the bacteria. Effects of lyoprotectant solutions containing 0.4 M sucrose, 0.4 M trehalose or 30 % (wt/wt) glycerol on the activity of the encapsulated bacteria during drying were investigated. It was determined that two orders of magnitude increase in the elastic modulus (E) and the compressive stress at failure (σ) of the gel could be achieved by drying, independent of the drying rate. It was shown that partially desiccated silica gels preserved and enhanced the biocatalytic activity of the encapsulated bacteria up to a critical drying level. Atrazine biodegradation activity of encapsulated bacteria suspended with 0.4 M sucrose and PBS increased with increasing water removal, reaching a maximum at 68 % water loss. This enhanced activity was sustained for 3 months, when the gels were stored at 4 °C.

Graphical Abstract

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6


  1. 1.

    Avnir D, Coradin T, Lev O, Livage J (2006) Recent bio-applications of sol–gel materials. J Mater Chem 16(11):1013–1030. doi:10.1039/b512706h

    Article  Google Scholar 

  2. 2.

    Meunier CF, Dandoy P, Su B-L (2010) Encapsulation of cells within silica matrixes: towards a new advance in the conception of living hybrid materials. J Colloid Interface Sci 342(2):211–224. doi:10.1016/j.jcis.2009.10.050

    Article  Google Scholar 

  3. 3.

    Blondeau M, Coradin T (2012) Living materials from sol–gel chemistry: current challenges and perspectives. J Mater Chem 22(42):22335–22343. doi:10.1039/c2jm33647b

    Article  Google Scholar 

  4. 4.

    Perullini M, Jobbagy M, Mouso N, Forchiassin F, Bilmes SA (2010) Silica-alginate-fungi biocomposites for remediation of polluted water. J Mater Chem 20(31):6479–6483. doi:10.1039/c0jm01144d

    Article  Google Scholar 

  5. 5.

    Branyik T, Kuncova G, Paca J, Demnerova K (1998) Encapsulation of microbial cells into silica gel. J Sol-Gel Sci Technol 13(1–3):283–287. doi:10.1023/a:1008655623452

    Article  Google Scholar 

  6. 6.

    Bartholomew CH (2001) Mechanisms of catalyst deactivation. Appl Catal Gener 212(1–2):17–60. doi:10.1016/s0926-860x(00)00843-7

    Article  Google Scholar 

  7. 7.

    Wu D, Zhou J, Li Y (2007) Mechanical strength of solid catalysts: recent developments and future prospects. AIChE J 53(10):2618–2629. doi:10.1002/aic.11291

    Article  Google Scholar 

  8. 8.

    Brinker CJ, Scherer GW (1990) Sol–gel science: the physics and chemistry of sol–gel processing. Academic Press, Massachusetts

    Google Scholar 

  9. 9.

    Rabinovich EM, Kurkjian CR, Kopylov NA, Fleming DA (1991) Mechanical strength of particulate silica-gels. J Mater Sci 26(24):6685–6692

    Article  Google Scholar 

  10. 10.

    Mackenzie JD, Huang QX, Iwamoto T (1996) Mechanical properties of ormosils. J Sol-Gel Sci Technol 7(3):151–161. doi:10.1007/bf00401034

    Article  Google Scholar 

  11. 11.

    Potts M (1994) Desiccation tolerance of prokaryotes. Microbiol Rev 58(4):755–805

    Google Scholar 

  12. 12.

    Leslie SB, Israeli E, Lighthart B, Crowe JH, Crowe LM (1995) Trehalose and sucrose protect both membranes and proteins in intact bacteria during drying. Appl Environ Microbiol 61(10):3592–3597

    Google Scholar 

  13. 13.

    Hubalek Z (2003) Protectants used in the cryopreservation of microorganisms. Cryobiology 46(3):205–229. doi:10.1016/s0011-2240(03)00046-4

    Article  Google Scholar 

  14. 14.

    Swift HF (1921) Preservation of stock cultures of bacteria by freezing and drying. J Exp Med 33(1):69–75

    Article  Google Scholar 

  15. 15.

    Nassif N, Bouvet O, Rager MN, Roux C, Coradin T, Livage J (2002) Living bacteria in silica gels. Nat Mater 1(1):42–44. doi:10.1038/nmat709

    Article  Google Scholar 

  16. 16.

    Perullini M, Amoura M, Roux C, Coradin T, Livage J, Laura Japas M, Jobbagy M, Bilmes SA (2011) Improving silica matrices for encapsulation of Escherichia coli using osmoprotectors. J Mater Chem 21(12):4546–4552. doi:10.1039/c0jm03948a

    Article  Google Scholar 

  17. 17.

    Klein S, Avrahami R, Zussman E, Beliavski M, Tarre S, Green M (2012) Encapsulation of Pseudomonas sp. ADP cells in electrospun microtubes for atrazine bioremediation. J Ind Microbiol Biotechnol 39(11):1605–1613. doi:10.1007/s10295-012-1164-3

    Article  Google Scholar 

  18. 18.

    Pannier A, Mkandawire M, Soltmann U, Pompe W, Bottcher H (2012) Biological activity and mechanical stability of sol–gel-based biofilters using the freeze-gelation technique for immobilization of Rhodococcus ruber. Appl Microbiol Biotechnol 93(4):1755–1767. doi:10.1007/s00253-011-3489-7

    Article  Google Scholar 

  19. 19.

    Mutlu BR, Yeom S, Tong H-W, Wackett LP, Aksan A (2013) Silicon alkoxide cross-linked silica nanoparticle gels for encapsulation of bacterial biocatalysts. J Mater Chem A 1(36):11051–11060. doi:10.1039/C3TA12303K

    Article  Google Scholar 

  20. 20.

    Jablonowski ND, Schaeffer A, Burauel P (2011) Still present after all these years: persistence plus potential toxicity raise questions about the use of atrazine. Environ Sci Pollut Res 18(2):328–331. doi:10.1007/s11356-010-0431-y

    Article  Google Scholar 

  21. 21.

    Reategui E, Reynolds E, Kasinkas L, Aggarwal A, Sadowsky MJ, Aksan A, Wackett LP (2012) Silica gel-encapsulated AtzA biocatalyst for atrazine biodegradation. Appl Microbiol Biotechnol 96(1):231–240. doi:10.1007/s00253-011-3821-2

    Article  Google Scholar 

  22. 22.

    deSouza ML, Sadowsky MJ, Wackett LP (1996) Atrazine chlorohydrolase from Pseudomonas sp. strain ADP: gene sequence, enzyme purification, and protein characterization. J Bacteriol 178(16):4894–4900

    Google Scholar 

  23. 23.

    Krupa I, Nedelcev T, Racko D, Lacik I (2010) Mechanical properties of silica hydrogels prepared and aged at physiological conditions: testing in the compression mode. J Sol-Gel Sci Technol 53(1):107–114. doi:10.1007/s10971-009-2064-5

    Article  Google Scholar 

  24. 24.

    Sampedro JG, Uribe S (2004) Trehalose-enzyme interactions result in structure stabilization and activity inhibition. The role of viscosity. Mol Cell Biochem 256(1–2):319–327. doi:10.1023/B:MCBI.0000009878.21929.eb

    Article  Google Scholar 

  25. 25.

    Galmarini MV, Baeza R, Sanchez V, Zamora MC, Chirife J (2011) Comparison of the viscosity of trehalose and sucrose solutions at various temperatures: effect of guar gum addition. Lwt-Food Sci Technol 44(1):186–190. doi:10.1016/j.lwt.2010.04.021

    Article  Google Scholar 

  26. 26.

    Luckey M, Nikaido H (1980) specificity of diffusion channels produced by lambda-phage receptor protein of Escherichia coli. Proc Natl Acad Sci USA Biol Sci 77(1):167–171. doi:10.1073/pnas.77.1.167

    Article  Google Scholar 

  27. 27.

    Wang YF, Dutzler R, Rizkallah PJ, Rosenbusch JP, Schirmer T (1997) Channel specificity: structural basis for sugar discrimination and differential flux rates in maltoporin. J Mol Biol 272(1):56–63. doi:10.1006/jmbi.1997.1224

    Article  Google Scholar 

  28. 28.

    Mutlu BR, Yeom S, Wackett LP, Aksan A (2014) Modelling and optimization of a bioremediation system utilizing silica gel encapsulated whole-cell biocatalyst. Chem Eng J. doi:10.1016/j.cej.2014.07.130

    Google Scholar 

  29. 29.

    Nassif N, Roux C, Coradin T, Rager MN, Bouvet OMM, Livage J (2003) A sol–gel matrix to preserve the viability of encapsulated bacteria. J Mater Chem 13(2):203–208. doi:10.1039/b210167j

    Article  Google Scholar 

  30. 30.

    de la Llave E, Molinero V, Scherlis DA (2010) Water filling of hydrophilic nanopores. J Chem Phys. doi:10.1063/1.3462964

    Google Scholar 

  31. 31.

    Alvarez GS, Desimone MF, Diaz LE (2007) Immobilization of bacteria in silica matrices using citric acid in the sol–gel process. Appl Microbiol Biotechnol 73(5):1059–1064. doi:10.1007/s00253-006-0580-6

    Article  Google Scholar 

Download references


We would like to thank Ms. Sujin Yeom for providing the bacteria. We would also like to thank Dr. Kelly Aukema, Dr. Adi Radian and Mr. Jonathan Sakkos for helpful discussions and providing feedback on the manuscript. We acknowledge the support of an NSF-IIP/PFI Grant (#1237754), a University of Minnesota Futures Grant and a MnDrive fellowship to BRM from the BioTechnology Institute in University of Minnesota.

Author information



Corresponding author

Correspondence to Alptekin Aksan.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary material 1 (DOCX 780 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Mutlu, B.R., Hirschey, K., Wackett, L.P. et al. Long-term preservation of silica gel-encapsulated bacterial biocatalysts by desiccation. J Sol-Gel Sci Technol 74, 823–833 (2015).

Download citation


  • Bioencapsulation
  • Bioremediation
  • Biocatalysis
  • Atrazine
  • Silica gel
  • Desiccation