Selection And Identification Of Strain With High-yield Bacterial Cellulose And Optimization Of Fermentation Process

Bacterial Cellulose (BC) is a kind of gelatinous membrane produced by bacteria such asAcetobacter on heterotrophic mechanism. Compared with plant fibers and animal fibers, it is akind of "super-pure" cellulose and isn’t mixed with any other polysaccharide. It has a lot ofgood qualities. BC has been widely used in the areas of food, high-grade acoustics, papermaking, oil drilling and medicine etc today.Persimmon vinegar with BC membrane was used as raw materials to isolate and obtain acellulose-producing strain with highproductivity and genetic stability, and the parameters offermentation process were optimized. Synthesis kinetics of the production was preliminarilyexplored and the structure and property of the BC was studied. The main research results areas follows:(1) Through separation and purification, a cellulose-producing strain—L96, with highproductivity and genetic stability was obtained. Accroding to the16S rDNA sequenceanalysis and phylogenetic tree analysis and physiological and biochemical analysis, this strainwas identified to be Gluconacetobacter xylinus.(2) The optimum cultivation conditions were as follows: seed ages20h, initial pH value4.0, inoculums amount11%, incubation time9d. The optimum fermentation medium were asfollows: sucrose5%(w/v), yeast extract0.9%(w/v), peptone0.5%(w/v), K2HPO40.3%(w/v),MgSO42%(w/v), acetic acid0.2%(v/v), ethanol1.5%(v/v). Using the optimized fermentationculture conditions and fermentation medium formula, the wet film weigh of BC was68.37g/100mL, which was as1.4times as that under initial fermentation medium(48.93g/100mL).(3) Bacteria density and BC production increased with the sugar concentration decreased.The fermentation process of producting BC belonged to the process of growth wasmembrane-associated. The pH value decreased with the bacteria density and BC productionincreased.(4) The average dry film weighs of BC synthesized by L96was0.37g/100mL, cellulosecontent in dry membrane was89.24%, protein content was6.33%, and fat content was0.96%.The images of scanning electron microscope (SEM) showed that BC synthesized by L96was ultrafine network structure. Moisture content of per gram of dried cellulose was130~210g, average rehydration rate of dried cellulose was70.60%.