Production Of Bacterial Cellulose And Characterization Of The Cellulose's Physicochemical Propeties

Bacterial cellulose (BC) is also by the name of Microbial Cellulose that is a natural polymer synthesized by bacteria. From the cellulose composition, BC is a linear condensation polymer consisting of D-anhydroglucopyranose units (glucose unit for convenience) joined together byβ-1,4-glycosidic bonds (thus a 1,4-β-D glucan) like plant cellulose. While to physical, chemistry and mechanical properties, it displays unique properties including high crystallinity, high water holding capacity, nanofibre-network structure, high tensile strength and elastic modulus. Due to its unusual material properties, BC has recently become a kind of attractive biomedical material in the international research that was extensively applied to food, paper, biomedical materials, acoustic diaphragms and so on.It is quite well known that BC is a secondary metabolite so that study on the influence of nutrient content on cellulose production is very important. This paper firstly investigated the changes of residual sugars, pH values and output of bacterial cellulose (BC) in Acetobacter xylinum static and shaking cultivations by using various carbon sources, initial pH, organic acids, ethanol and so on.In static cultivations, the results indicated that among four carbon sources, the highest BC yield was obtained using mannitol. The optimal initial pH for getting the highest yield was 4.5, while bacteria grew well at pH 4-6. The addition of ethanol or organic acids like acetic acid and lactic acid did not increase but decreased in yield of BC to different extent. And the addition of metal ions such as Fe²⁺, Mg²⁺, Ca²⁺ had different influence on cellulose output in various concentration range. By adding 0.1 mmol/L Fe²⁺, 7 mmol/L Mg²⁺, 5 mmol/L Ca²⁺, the production of BC was increased by 34.6%, 32.2% and 10.6% respectively.In shaking cultivations, the results indicated that among three carbon sources, the highest BC yield was also obtained using mannitol. The optimal initial pH for getting the highest yield was 5.0, while bacteria grew well at pH 4-7. By adding 3 mmol/L Fe²⁺ , 5 mmol/L Mg²⁺ , 5 mmol/L Ca²⁺, the production of BC was increased by 78.2%, 132.1% and 169.8% respectively. And the addition of 100 mmol/L lactic acid, 500 mmol/L ethanol, 200 mmol/L acetic acid, 1 mmol/L oxalic acid as well as 30 mmol/L citric acid had obvious effect on increasing yield of BC, the output was increased by 427.8%, 357.7%, 234.7%, 63.2%, 17.7% respectively. The concentration of the sucrose in the medium has been shown to have an important effect on the cellulose production. And the yield of BC was highest in the sucrose concentration of 40 g/L. In addition, by orthogonal design of experiment, the production of BC is 1.342 g/L, increased by 16.3 times using the optimized medium, which consisted of sucrose 25 g/L, ethanol 400 mmol/L and pH 4.5.The experimental investigations on physical, chemistry properties of BC such as shape, fiber network structure, diameter distribution, infrared spectrum diagnostics, thermo-gravimetric analysis (TGA), the containing water ratio and water absorption ratio, solubility of bacterial cellulose were carried out by using the scanning electron microscope (SEM), fourier transform infrared (FTIR) analyzer, thermo-gravimetric analyzer and so on. The obtained important data could apply to medical applications.