Team:Oxford/biopolymer containment
From 2014.igem.org
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- | <h1blue2>Maximise rate.</h1blue2> | + | <h1blue2>1. Maximise rate.</h1blue2> |
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A primary function of the beads is to maximise reaction rate per bead volume; halving the radius of a sphere doubles its surface area:volume ratio. Many, small, bacteria-embedded agarose beads (to a technical limit) are therefore optimal, as the average bacterium is closer to the surface of each bead and being ‘used’ more efficiently. Substrate molecules which follow Brownian motion are more likely to collide with and be broken down by ‘outer’ bacteria. Similarly, on average, product molecules have a shorter path length to the surface and are likely to diffuse out faster: | A primary function of the beads is to maximise reaction rate per bead volume; halving the radius of a sphere doubles its surface area:volume ratio. Many, small, bacteria-embedded agarose beads (to a technical limit) are therefore optimal, as the average bacterium is closer to the surface of each bead and being ‘used’ more efficiently. Substrate molecules which follow Brownian motion are more likely to collide with and be broken down by ‘outer’ bacteria. Similarly, on average, product molecules have a shorter path length to the surface and are likely to diffuse out faster: | ||
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- | <img src="https://static.igem.org/mediawiki/2014/ | + | <img src="https://static.igem.org/mediawiki/2014/d/d1/Oxford_polymer2.png" style="float:right;position:relative; width:40%;" /> |
- | + | <h1blue2>2. Protect bacteria</h1blue2> | |
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+ | For this system and others of its type, it is highly valuable to maximise local substrate concentration to the bacteria within the viable range of toxicity, especially while the viable concentration range to the strain remains a limitation to the breakdown rate (directly or indirectly). | ||
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+ | In our case, the diffusion-limiting polymer chosen was cellulose acetate (as its synthesis from cellulose is straightforward and safe) for which we modeled diffusion data for variable polymer thickness (see below). Acetylation stoichiometry or even polymer type entirely, polymer density and methods of bead coating are among many variables that can be further researched and optimised for desirable diffusion coefficients. | ||
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+ | As bacteria need direct access to water, yet DCM is water-soluble only up to ~200mM, for limited water-solubility substrates, as part of future research, we propose suspending beads at the interface of a biphasic mixture of the two by exploiting differences in density. In such a system, the immediate substrate ‘reservoir’ is essentially maximised. | ||
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+ | For the purposes of this project we opted to construct beads less dense than water, as the aqueous DCM concentration of the biphasic system is more reliable, and we had yet to establish the robustness of the diffusion-limiting system to external fluctuations in [DCM]. | ||
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Revision as of 18:55, 28 September 2014