Team:JNFLS/Design
After several times of brainstorm, we decided to use bacterial cellulose instead of polypropylene, to make medical mask because it is biodegradable.
1.Features of the bacterial cellulose (why we choose the bacterial cellulose)
Bacterial cellulose is an organic compound with the formula (C6H10O5)n produced by certain types of bacteria. Bacterial cellulose and natural cellulose produced by plants or seaweeds have the same molecular structural units, but bacterial cellulose fibers have many unique properties.
①Compared with plant cellulose, bacterial cellulose has no associated products such as lignin, pectin and hemicellulose, and has high crystallinity (up to 95%, 65% for plant cellulose) and high degree of polymerization (DP Value 2 000～8 000);
②Super fine mesh structure. Bacterial cellulose fibers are composed of microfibers with a diameter of 3 to 4 nanometers combined into fiber bundles with a thickness of 40 to 60 nanometers, which are interwoven to form a developed ultra-fine network structure;
③The elastic modulus of bacterial cellulose is several to ten times that of general plant fibers, and the tensile strength is high;
④Bacterial cellulose has strong water holding capacity. The WRV value of undried bacterial cellulose is as high as 1000%, and the water holding capacity after freeze-drying still exceeds 600%. The swelling capacity of the bacterial cellulose dried at 100°C in water is equivalent to that of cotton linters;
⑤Bacterial cellulose has high biocompatibility, adaptability and good biodegradability;
⑥The controllability of bacterial cellulose biosynthesis.
2. The applications of bacterial cellulose at present
2.1 Textile material
The molecular structure of bacterial cellulose is similar to that of plant cellulose, and it has such unique properties as high tensile strength, high porosity and nano-fiber structure, which can improve the deficiency of original products or prepare textiles with better performance. Using bacterial cellulose instead of plant cellulose has great economic value, which can not only make full use of industrial waste, reduce pollution, but also shorten the growth cycle of cellulose, increase the yield of cellulose, and realize the industrial production of cellulose.
2.2 Electromagnetic material
Due to its high reflectivity, elasticity and dimensional stability, cellulose is suitable to be used as a medium for information display. For example, bacterial cellulose is used to make "electronic paper" and then to make electronic liquid crystal screen, which can be potentially used in electronic sensors, information storage, electronic shielding coating and anti-false and other fields. In addition, the nanostructure and high porosity of bacterial cellulose also make it suitable as a substrate to prepare proton conductive films and organic light-emitting diodes with adsorption and transport properties, which can be used in biosensors, biofuel cells and other fields.
2.3 The medicinal materials
Bacterial cellulose has high water retention, good air permeability, good biocompatibility and good mechanical properties, so it has a broad application prospect in the medical dressing industry. Research shows that serving as bandages, gauze and band-aids, it can reduce the wound stimulation, effectively relieve pain, accelerate wound healing and other good properties. Due to its lack of antibacterial effect, bacterial cellulose can also be modified by composite technology to give it good antibacterial properties, so that it has a better application prospect in medical dressing. In addition, due to its unique fiber network structure, high porosity, high mechanical strength and high elastic modulus, bacterial cellulose is also an ideal scaffold for the growth of epithelial cells and an ideal substitute material for scaffolds for artificial skin, arteries and veins, and bone tissue.
Moreover, some researchers also used bacterial cellulose to make facial mask because of its high water retention and good air permeability.
2.4 others
In addition to being used as high-value-added medical materials, multi-functional textiles, functional foods and electro-magnetic materials, bacterial cellulose has also achieved remarkable results in the environmental industry, such as the application of bacterial cellulose membrane adsorption or filtration to remove many heavy metal ions in wastewater. Due to its high Young's modulus and shape maintaining ability, it can also be used in building materials in the future to increase stability.
However, we intended to use bacterial cellulose to make medical mask. As far as we know, no one has studied it in this research field before.
In nature, there are many bacteria that can effectively produce cellulose, the most common is acetobacter xylinus. In the past, most studies on bacterial cellulose focused on the separation strains, and optimization of fermentation medium and culture conditions, etc. However, low yield and high cost are still a bottleneck for the large-scale production and industrialization of bacterial cellulose. In order to effectively solve this problem, we plan to clone the genes related to cellulose synthesis in the acetobacter xylinus, and transfer them to the engineered E. coli, hoping to be able to produce bacterial cellulose using E. coli.
3. How bacterial cellulose(BC) is produced in acetobacter xylinus?
Acetobacter xylinus can use many carbon sources to produce cellulose. Glucose is the most common carbon source. There are four steps involved in the chemical reaction from glucose to bacterial cellulose: Glucose hexokinase (GHK), Phosphoglucomutase (PGM), UDP-glucose pyrophosphorylase (UGPase), and Bacterial cellulose synthase (Bcs). These four involved enzymes catalyze the following reactions:
In addition to these four enzymes, some other protein or enzymes are essential. The CcpAx protein, also known as ORF-2, functions as a mediator of protein-protein interactions and is important for localization of the bacterial cellulose synthase complex to the cell membrane. Endo-β-1,4-glucanase(CMCax) and β-glucosidase both can hydrolyze tangled glucan chains when there is a failure chain arrangement and are both crucial for bacterial cellulose synthesis.
4. Design of our project
Based on the mechanism of BC synthesis, we were going to clone 6 protein or enzymes genes required for BC synthesis and transfer them to the E. coli.
In order to increase the practicality of bacterial cellulose, we plan to add Spirooxazine, a photosensitive compound, to the culture of E. coli. This photosensitive compound can show light blue under light conditions, so that the synthetic bacterial cellulose can also have the function of color changing, which can increase the beauty of masks. In addition, by adding a small amount of chitosan to the fermentation medium for several times, the production of chitosan/cellulose composite material synthesized in situ can be realized, so that the prepared mask has antibacterial properties.
5. Innovation of our project
5.1 We did not find research that using BC to produce masks in the published papers. Maybe this is the biggest novelty of our project.
5.2 The proposed the mask has the color changing and antibacterial properties.
5.3 In this era of viral epidemics, we need to wear masks frequently. However, sometimes we need to remove the mask when we're doing face recognition. It's very inconvenient. Our masks, made of bacterial cellulose, are translucent, enabling face recognition without removing the mask. This is amazing!
References:
[1]Selestina Gorgieva and Janja Trˇcek. Bacterial Cellulose: Production, Modification and
Perspectives in Biomedical Applications. Nanomaterials, 2019, 9: 1352-1371.
[2]Thanaporn Amnuaikit, Toon Chusuit, and Panithi Raknam, et al. Effects of a cellulose mask synthesized by a bacterium on facial skin characteristics and user satisfaction. Medical Devices: Evidence and Research, 2011, 4: 77-80.