Preparation Of Bacterial Cellulose Composites Based On Static Fermentation And The Investigation Of Their Properties And Application

Bacterial cellulose is a natural nanocellulose produced by bacteria.It has the advantages of natural 3D network structure,large specific surface area,high crystallinity,high mechanical strength,high hydrophilicity,high transparency,high biosafety and biodegradability.These excellent characteristics make it widely used in food additives,beauty cosmetics,biomedicine,flexible electronics,energy storage devices,and other fields.It needs a lot of carbon source to produce bacterial cellulose,which makes the production cost of bacterial cellulose is higher,and the fermentation cycle is long.Pure bacterial cellulose does not have diverse functions.In order to expand the applications,bacterial cellulose should be chemically modified on its surface.But the restricted water in bacterial cellulose hydrogel limits the diffusion of reactants in the gel,increasing the difficulty of modification reaction.Usually,chemical modification may also weaken the mechanical properties of bacterial cellulose hydrogels.Therefore,the production of high-strength nanocellulose hydrogels by microbial fermentation is faced with problems such as limited productivity,high cost and difficulty in functionalization.In order to solve the above problems,we developed a method to efficiently produce high-strength bacterial cellulose composites based on microbial static fermentation technology.In the process of microbial static fermentation,biomass nanomaterials from different sources were regularly and quantitatively supplied via an automatic spray method.The bacterial cellulose synthesized in situ by microorganisms tangled with the biomass nanomaterials through intermolecular interactions,including hydrogen bonding and electrostatic interaction,and formed a natural three-dimensional network structure.Biomass nanomaterials had a wide range of sources and were rich in chemical groups on their surfaces.On one hand,biomass nanomaterials could be used to improve the productivity of microbial fermentation.On the other hand,the functionalization of bacterial cellulose can be achieved by incorporating biomass nanomaterials with native chemical groups,or the biomass nanomaterials with additional modification before fermentation.In this study,we developed a static fermentation device incorporated with an automatic spray equipment,and selected the Acetobacter xylinum as mode bacteria.We synthesized three kinds of biomass nanomaterials including physically-fibrillated cellulose nanofibers,carboxymethylated cellulose nanofibers and chitosan nanofibers.By incorporating these three biomass nanomaterials into the network of bacterial cellulose through automatic spray,we obtained three kinds of bacterial cellulose/biomass nanofibers composites.The strategy successfully enhanced the yield of bacterial cellulose hydrogel by 0.3-1.3 times.The microstructure of the composite was characterized.It was found that the composite nanomaterials formed similar network structure with the one of bacterial cellulose,and the composite still maintained high crystallinity and excellent mechanical properties.The bacterial cellulose/chitosan nanofiber composite(BC/CSNF)exhibited great anti-bacterial capability on both Gramnegative Escherichia coli and Gram-positive Staphylococcus aureus,which facilitated its biomedical application in wound dressing,hemostatic material and so on.In summary,we successfully prepared a variety of bacterial cellulose/biomass nanomaterial composites via a static fermentation device armed with an automatic spray equipment,which improved the yield of bacterial cellulose and faciliated the functionalization of bacterial cellulose.Overall,our study developed a new strategy for the preparation of bacterial cellulose composite and their application.