Issue 36, 2013
From the journal:

Journal of Materials Chemistry A

Silicon alkoxide cross-linked silicananoparticle gels for encapsulation of bacterial biocatalysts

Baris R. Mutlu,a   Sujin Yeom,b   Ho-Wang Tong,a   Lawrence P. Wackettcd  and  Alptekin Aksan*ad  

* Corresponding authors

a Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
E-mail: aaksan@umn.edu

b Department of Microbiology, University of Minnesota, Minneapolis, MN 55455, USA

c Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA

d BioTechnology Institute, University of Minnesota, Saint Paul, MN 55108, USA

Abstract

A method is developed for encapsulation of bacterial biocatalysts in silica gels formed by silica nanoparticles (SNP) and a silicon alkoxide crosslinker. Formulation of the gel was optimized by changing the SNP size, SNP to crosslinker ratio and crosslinker functionality. Hydrolysis and condensation reactions of silicon alkoxide were controlled by water to alkoxide ratio (r) and pH of the solution. FTIR analysis verified that a reactive and temporally stable silicon alkoxide crosslinker was obtained. As a case study, recombinant Escherichia coli (E. coli) cells expressing the atrazine dechlorinating enzyme AtzA were encapsulated. Synthesized catalytic biomaterials (silica gel encapsulated bacterial biocatalysts) were evaluated based on their gelation time, biocatalytic activity and mechanical strength. Diffusivity assays and SEM were used for characterization of the gel structure. We found that SNP to crosslinker ratio affected all the features of the gel, whereas crosslinker functionality primarily affected the gelation time and SNP size affected the mechanical strength and diffusivity. Based on systematic evaluation, we selected three gel formulations and subjected them to long-term activity measurements in a continuous-flow bioreactor for removing trace levels of atrazine. The effluent atrazine concentration was sustained below 30% of the influent concentration, <3 ppb, for 2 months.

Graphical abstract: Silicon alkoxide cross-linked silica nanoparticle gels for encapsulation of bacterial biocatalysts

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Article information

DOI
https://doi.org/10.1039/C3TA12303K
Article type
Paper
Submitted
13 Jun 2013
Accepted
24 Jul 2013
First published
25 Jul 2013

J. Mater. Chem. A, 2013,1, 11051-11060

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Silicon alkoxide cross-linked silica nanoparticle gels for encapsulation of bacterial biocatalysts

B. R. Mutlu, S. Yeom, H. Tong, L. P. Wackett and A. Aksan, J. Mater. Chem. A, 2013, 1, 11051 DOI: 10.1039/C3TA12303K

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