Study On Production Of Bacterial Cellulose With Different Gluconacetobacter Xylinus Strains

Bacterial cellulose(BC) is a pure cellulose synthesized by microbial cells. It is widely applicatied in the field of food ingredients, paper industry, cosmetics, medical materials for its excellent physical and chemical properties.Its wide application and large-scale production is limited in the low yield of BC which is one of the main factors. The low productivity of the BC-producing strains is the main factor that caused the low yield of bacterial cellulose. Therefore, to improve the production efficiency of the producing strains is the important solution. Gluconacetobacter xylinus is an important bacterial cellulose producing strain and different species of Gluconacetobacter bacteria have different physiological and biochemical characteristics. Besides, the production process of different strans is also distinct from each other.This study chose four G·xylinus strains(DHU-ZCY-1, DHU-YQ-1, DHU-ZGD-1,DHU-ATCC-1) to produce BC compared with G·xylinus ATCC23770 by static culture. This study chose the D-glucose and D-fructose as the carbon source. The effects of sugar concentrations on the growth of the bacteria, the determination of bioconversion products in the medium, the changes of pH value, the consumption of carbon source and the yield of BC were studied. X-ray diffraction analysis and scanning electron microscopy and universal material testing machine bacterial cellulose were used to characterize BC.The major results of the dissertation are summarized as follows:1. Using the D-glucose with concentrations of 40 g/L as the carbon source as the feedstock, the effect of different strains on the production of BC was studied. The result revealed that the DHU-ZCY-1 was the best G. xylinus strain could utilize the D-xylose with concentrations of 40 g/L to produce BC, the yield of BC was as high as 3.91 g/L. It showed that different strains had different effect and the influencing order of the strains from strong to weak was DHU-ZCY-1> DHU-ATCC-1 > DHU-ZGD-1 > DHU-YQ-1 > ATCC23770. The Elastic Modulusof BC made by DHU-ZGD-1was as high as 10 KPa. It was four times high than that made by DHU-ATCC-1.2. Using the D-glucose with concentrations of 80 g/L as the carbon source as the feedstock, the effect of different strains on the production of BC was studied. The result revealed that the DHU-ZGD-1 was the best G. xylinus strain could utilize the D-xylose with concentrations of 80 g/L to produce BC, the yield of BC was as high as 4.73 g/L. It showed that different strains had different effect and the influencing order of the strains from strong to weak was DHU-ZGD-1> DHU-ATCC-1> DHU-ZCY-1> ATCC-23770 > DHU-YQ-1. The Elastic Modulusof BC made by DHU-ATCC-1 was as high as 4.3 KPa. It was four times high than that made by DHU-YQ-1.3. Using the D-fructose with concentrations of 40 g/L as the carbon source as the feedstock, the effect of different strains on the production of BC was studied. The result revealed that the DHU-ZGD-1 was the best G. xylinus strain could utilize the D-xylose with concentrations of 40 g/L to produce BC, the yield of BC was as high as 2.2 g/L. It showed that different strains had different effect and the influencing order of the strains from strong to weak was DHU-ZGD-1 > DHU-ZCY- 1> DHU-ATCC-1 > DHU-YQ-1 > ATCC23770.The Elastic Modulusof BC made by DHU-ZGD-1 was as high as 10 KPa. It was six times high than that made by DHU-ATCC-1.4. Using the D- fructose with concentrations of 80 g/L as the carbon source as the feedstock, the effect of different strains on the production of BC was studied. The result revealed that the DHU-ZGD-1 was the best G. xylinus strain could utilize the D-xylose with concentrations of 80 g/L to produce BC, the yield of BC was as high as 3.26 g/L. It showed that different strains had different effect and the influencing order of the strains from strong to weak was DHU-ZGD-1 > DHU-ZCY-1 > DHU-ATCC-1 > DHU-YQ-1 > ATCC23770. The Elastic Modulusof BC made by DHU-ZGD-1 was as high as 6.3 KPa. It was three times high than that made by DHU-ZCY-1.The above investigation indicated that different G. xylinusm strains had the strongest effect on BC yield and performance. The difference in the utilization efficiency of sugars by the microorganisms was probably due to the different metabolic pathway that they took part in.