New High Polymer Material——Screening Of High-yield Strains Of Bacterial Cellulose And Researching Of The Cellulose Synthesis Conditions

Bacterial cellulose, a novel polymeric material, is synthesized by microorganisms under the precise regulation of the multi-enzyme complex systems which make glucopyranose residues transferred to the newly generated dextran chain with uridine diphosphate glucose as precursor, secreted into the extracellular matrix through the outer membrane, and finally formed the supramolecular organization structure by the assembly, crystallization and combinations of multiple dextran chains. Compared with artificially synthesized cellulose and photosynthesized plant cellulose, bacterial cellulose has unparalleled excellent performance, high crystallinity, high purity, high synthesis rate and high yield, as well as environmentally friendly. Bacterial cellulose, therefore, has great values in the fields of food, paper making, electronics and biomedical.This paper high-yield strains of bacterial cellulose were screened of from the vinegar grains, kombucha liquid, defective fruits, and other materials, and made a research on product characteristics. Synthesis conditions of the product were optimized via response surface method. In addition, synthesis kinetics of the product was preliminarily explored. All the work provided some basis for the industrial production of bacterial cellulose.After repeated screening, we have obtained a strain AXB(X), with high-yield of bacterial cellulose, from the homemade Kombucha liquid, the initial yield of2.20g/L and stability. We determined that the strain belongs to Gluconacetobacter sp. through colony morphology, microscopic morphological observation, physiological and biochemical tests and16SrDNA identification results.We could confirm that the main ingredient of the product is cellulose by color reaction and fourier transform infrared identification. And through X-ray diffraction analysis we concluded that the crystal form of the product is cellulose type Ⅰ. Enzymolysis and acidolysis experiments showed that high purity (over95%) and water holdup (over95%) of the product. Observing the surface morphology of the product through scanning electron microscopy, it revealed that fibers interwoven with ultra-fine precision porous network structure.The various factors that affect the synthesis of bacterial cellulose were investigated through the single factor experiment, tentatively identified the significant factors and concentration range. Furthermore, Plackett-Burman and Box-Benhnken Design experimental were designed using the Minitab software, combined with SAS software analysis. Ultimately, we obtained optimized synthesis conditions combination:sweet potato enzymatic hydrolyzate5%, peptone0.5%, yeast extract0.5%, trisodium phosphate0.4%, citric acid0.113%, magnesium sulfate0.02%, pH6.0, liquid volume in flask50ml/250ml, adding ethanol volume fraction2%after sterilization, bacterial cellulose production at least in the4.80g/L, more than118%before optimization.Finally, synthesis kinetics studies have shown that bacterial cellulose synthesis and cell concentration were positively correlated. With the time of48-132h, the pH in the range of3.32to3.64, the cell concentration increasing with the form of index, while the synthesis of bacterial cellulose accumulating in an exponential form.