Team:Shanghai YGQ/Design
Design
Our Goal:
Adding antibacterial substance during the process of making bacterial cellulose membrane.
We had gone though these steps:
1. Looking for the right base
2. Choosing the right antibacterial substance
3. Production of antibacterial substance
4. How to regulate its production
The first is the base, we have considered transferring the gene sequence for producing b acterial cellulose and the gene sequence for producing chitosan into E. coli. However, we found that the current highest yielding strain, Acetobacter xylinum, its QS (quorum sensing system) is of great help to the subsequent regulation, and the genetic sequence that needs to be transferred is reduced.
Secondly, the choice of antibacterial substances. After consulting a large amount of document, we found that chitosan is an antibacterial substance, which is easily dissolved in a weak acid solvent. The dissolved solution contains amino groups (NH2+), which combine negative electrons to inhibit bacteria. It has a wide range of applications in the fields of medicine, textiles, and food.
It can be directly synthesized by chitin deacetylase, and the sequence corresponding to this enzyme has been used by others before. In this way, chitosan can be gradually combined with chemical residues on the bacterial cellulose membrane during the production process. However, due to its antibacterial properties, the production of bacterial cellulose is also affected.
To solve the problem of bacterial cellulose being affected, we used a quorum-sensing system. Which means during the growth process of the microbial population, due to the increase of the population density, the physiological and biochemical characteristics of the microbial population are changed and shows the characteristics of a small number of cells or single cells that are not found.
The reason for this change is that when the microbial population density reaches a threshold in the environment, and the concentration of the signal molecule reaches a certain level, the signal transmission of the related protein including the receptor protein, the induction or inhibition signal is finally transmitted to the intracellular, affecting the specific expression of genes regulates the physiological characteristics of the microbial population, such as bioluminescence, antibiotic synthesis, biofilm formation, and the other.
Using the QS mechanism for "cell-to-cell communication," microbes can be coordinated in a complex environment to make the entire population survive better. The quorum-sensing system enables bacteria to produce chitosan after reaching a certain population density, thereby reducing the effect of chitosan on cellulose production.