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Team:Imperial/Project
From 2014.igem.org
Project
Introduction
This summer we looked into the potential of bacterial cellulose as a modularly functionalisable biomaterial. In our project we optimise the production of bacterial cellulose by engineering Gluconacetobacter xylinus and transferring the system into E. coli. We also functionalise our cellulose in order to expand its mechanical, chemical and biological properties into new areas of use.
Background
Cellulose is the most abundant organic polymer found in nature. Due to its versatility and ubiquity we find cellulose has applications in areas from medicine to textiles.Much of the cellulose we use is impure as it is derived from plants. Bacteria offer an alternative means of production that produces a cellulose that is purer and requires less processing.
G. xylinus
Cellulose is naturally produced by bacteria of several genera as an extracellular matrix. This functions as a protective mechanism, shielding the bacteria from the environment. The gram-negative Gluconacetobacter xylinus (formerly Acetobacter xylinum) is a high-yielding producer of bacterial cellulose and so served as a suitable base for further optimisation.
E. coli
While Gluconacetobacter is a high producer of bacterial cellulose, E. coli is currently a more robust host for synthetic biology. Transferring the bacterial cellulose operon into E. coli would ease further in-vivo modification of the cellulose by allowing well characterised parts to be used more directly and has the potential for higher productivity.
Functionalisation
Pure bacterial cellulose is itself a useful biomaterial with material properties that facilitate applications from filtration to wound dressing. We modify the material, chemical and biological properties of our biomaterial through the addition of functional proteins. We investigated different methods of coupling these to the cellulose.
E. coli
While Gluconacetobacter is a high producer of bacterial cellulose, E. coli is currently a more robust host for synthetic biology. Transferring the bacterial cellulose operon into E. coli would ease further in-vivo modification of the cellulose by allowing well characterised parts to be used more directly and has the potential for higher productivity.
Co-Culturing
The idea of combining E. coli as an efficient cloning organism since it has the largest library of well characterised parts available and G. xylinus as a robust efficient cellulose producing host came about as a way to take advantage of the characteristics of each host.
Mass Production and Processing
To produce a useable material from the wet pellicle we grew up cellulose in bulk in order to experiment with various methods of treating and processing it.This produced materials with a range of properties.
Tensile Testing
Having produced large quantities of bacterial cellulose, it is key to quantify the quality of our biomaterial. This determines the water flow rates that can be expected in a membrane bioreactor water filtration setup.
