Properties of Cellulose:
A bacterially synthesized cellulose fiber shows exceptional material properties such as high chemical and thermal stability, biocompatibility and bioinertness and high mechanical stability. The diameter of a bacterial cellulose fiber is about 40-60 nm, which corresponds to one- hundredth of the diameter of a plant fiber. The modulus of elasticity is about 134 GPa, which can be compared with the one of cast iron (grey cast iron: E = 90 - 140 GPa). A single fiber shows the tensile strength of 2 GPa, this is comparable with some stainless steel types like AK steel (AK Steel 17-7 PH: Rm = 1,3 - 1,5 GPa).[6],[7],[8],[9]
The study of the iGEM Team of the Imperial College London (2014) advises a maximum working shear stress of 7.5 MPa.[10]
The nano structured system shows a large specific surface (60-100 m2/g), this is responsible for the possibility of intense interactions.[6]
One example is the link of cellulose binding domains (CBDs) to the cellulose matrix by hydropbobic interactions. Genetic engineering is our solution for the attachment of the Flagellas on our surface material. This means an effective immobilization of CBD-flagellin fusion proteins on the cellulose matrix without the need for covalent cross linking. The results of Kauffmann et al. (2000) show that the CBD causes no activity loss of the attached protein. In addition immobilization often results in a higher stability of the protein.[11]
Life-time of the product:
The estimated half-life of cellulose itself at 25° C is about 5-8 million years. It can be degraded aerobically and anaerobically. The degradation is catalyzed by a range of enzymes in cellulolytic microorganisms. Three types of enzymes are involved in the degradation process: endoglucanases, cellobiohydrolases, and β-glucosidases.
The known enzymes responsible for cellulose degradation, as well as the cleavage sites, are shown in table 1.