One way of assessing the feasibility of the synergistic approach to biorefineries is to use in silico modelling. In particular, we would like to confirm that synergistic use of enzymes can make the process of cellulose degradation more efficient.
Some other models, calculations, and tools were also developed by the team.
As it happens, our team includes:
- Two engineers experienced in using MATLAB.
- An informatician who quickly learned the Kappa modelling language.
- A biologist who, for no good reason, knows the C programming language.
This led to three different attempts to model cellulase action.
- C model — a simple model that showed a difference between synergistic and non-synergistic systems
- Kappa model — a more complex model that also showed a difference
- MATLAB model — the most complex model, only worked well for the non-synergistic system
Comparison of different modelling tools
Our analysis of the advantages and disadvantages of the various modelling approaches, together with conclusions, are on our model comparison page.
Other models and calculations
Consider this: for bacteria to produce phage or INP requires energy. This energy could have been spent producing extra copies of the cellulases. In order for the phage and cell display projects to make sense, the benefits of synergy must outweigh the cost of producing all these extra proteins.
This question can probably be investigated using simple maths and back-of-envelope calculations...
Evolutionary analysis of cell-display vs. secretion
One potential benefit of attaching enzymes to the cell surface rather than secreting them into the media is that any mutations that increase enzyme efficiency will specifically benefit the cell with the mutation, as the increased sugar yield will be physically present at the cell. The mutation will thus confer a fitness advantage, potentially allowing it to take over the culture.
By contrast, if a cell produces a secreted protein that is of higher efficiency, it will disperse and benefit random cells in the culture. To investigate this difference, we created our artificial selection model.
The phage display system requires infected E. coli to dominate the system and not be outcompeted by uninfected E. coli. Our phage replication model verifies that this is indeed the expected outcome.
Genetic Stability Tool
Our projects involve having multiple fusion proteins expressed, each of which uses a genetically identical carrier protein (e.g. ice-nucleation protein or the M13 pVIII gene). The presence of repeated sequences in DNA (i.e. the same sequence in multiple locations) can lead to genetic instability.
However, it ought to be possible to design and synthesise different versions of the genes that code for the same amino acids but use different codons and so are as distinct as possible.
To prove this, we made our Genetic Stability Tool.
- Van Zyl WH, Lynd LR, Den Haan R, McBride EJ (2007) Consolidated bioprocessing for bioethanol production using Saccharomyces cerevisiae. Advances in Biochemical Engineering/Biotechnology 108: 205-235 (doi: 10.1007/10_2007_061).