The Study Of Biosynthesis Glcnac-bc Copolymer And Mechanism

Coconut-water was used as the main culture medium to synthesize bacterial cellulose by Acetobacter xylinum in this paper. N-Acetyl-D-glucosamine (GlcNAc) was addec in the medium to prepare GlcNAc-BC copolymer with GlcNAc residual in the product molecule. The structure and performance of the product were studied. In order to explore tha metabolism mechanism of the added carbon source, a method of testing the content of N-Acetyl-D-glucosamine in the coconut-water medium by high performance liquid chromatography (HPLC) was established. The carbon sources consumption during the synthesis process and pH values were determined.BC could be obtained in short period and high yield in the coconut-water culture system prepared. The yield of GlcNAc added medium decreased than that of the contol system. When20g/L GlcNAc was added, the yield dropped to the lowest3.78g/L. But the water holding capacity of GlcNAc-BC increased than BC. When15g/L GlcNAc was added, the water holding capacity of GlcNAc-BC was the biggest1:128. SEM images showed BC with three dimensional network structure, compact and packing. The net holes of GlcNAc-BCs were larger than that of pure BC. FTIR spectra of GlcNAc-BC Samples preserved all characteristic peaks of pure BC, and still appeared one amide characteristic peaks of1560cm-1and acylamino1650cm-1. XRD profiles of the products displayed bacterial cellulose crystallization indexes were higher, but that of GlcNAc-BCs changed.TG tests showed thermal stabilities of GlcNAc-BCs reduced. XPS test showed grafting quantity of GlcNAc-BCs less. GPC results showed BC was a kind of high molecular weight of material. With the increase of GlcNAc adding in the medium, the molecular weight of the products almost keep the same.During the synthesis process of cultivation, the pH value of the control medium and GlcNAc culture medium was both gradually decreasing. Compared with the control medium, pH of GlcNAc added medium was always higher and decreased delayed. Total sugar contents of control medium and GlcNAc added medium changed with the similar trends. In the beginning3days, total sugar reduced sharply, especially in the second and the third day it reduced fastest. From the fourth day,the decreasing becomed slow. And total sugar consumption of the control medium was fastest. When the amount of GlcNAc added increased in the sysytem, total sugar consumption decreases gradually. The method of testing the medium GlcNAc content of coconut-water by high performance liquid chromatography (HPLC) was operation conveniently and high resolution. The control medium in the whole process of cultivation always did not exist GlcNAc. GlcNAc content of add GlcNAc medium in the earliest2days unchanged. Sucrose, glucose and fructose consumption trend of coconut-water medium was similar. Glucose consumption was the fastest in the first3days. Sugar and fructose contents slowly decreased. Then contents decreased slowly.