Production Of Bacterial Cellulose With Gluconacetobacter Xylinum Fermentation

Effect of Gluconacetobacter xylinum AS1.1812 and NLQ127 on the production and structure of bacterial cellulose was investigated in this paper.Field emission scanning electron microscopy?SEM?,Fourier infrared spectroscopy?FTIR?,X ray diffraction?XRD?were used to characterize bacterial cellulose obtained from different caobon sources and fermentation methods.A new approach of bacterial cellulose fermentation by Gluconacetobacter xylinum was established.This study provides an important theoretical basis for industrial production and extensive application of bacterial cellulose.The difference of Gluconacetobacter xylinum AS1.1812 and NLQ127 on the growth of bacteria,the consume of carbon source,the production and performance of bacterial cellulose were compared,and the strain with higher bacterial cellulose production ability was determined.The results showed that strain AS1.1812 had obvious growth advantages than NLQ127,but Gluconacetobacter xylinum NLQ127 had higher membrane production ability.Cultivated with different carbon sources,the bacterial cellulose production ability of AS1.1812 was concluded as follow:glucose,mannitol,xylose,fructose,sucrose.However,Strain NLQ127 was concluded as follow:glucose,fructose,mannitol,xylose,sucrose.Bacterial cellulose produced by strain AS1.1812 had no regular three-dimensional structure that composed of long fibrous filament;in constract,bacterial cellulose obtained from NLQ127 using hexose as carbon source was long and sturdy,the three-dimensional contour of the fiber was distinct and regular.When the xylose was used as carbon source,the cellulose network was slender,but the fiber diameter was significantly smaller than that from hexose.The culture medium and fermentation conditions of strain NLQ127 were optimized.Medium composition,fermentation conditions and the effect of additives on the production and morphology of bacterial cellulose were investigated.It is found that glucose and soybean peptone are the optimal carbon and nitrogen source.Inorganic salts,including MgSO₄,KH₂PO₄ and Na₂HPO₄,can promote the production of cellulose.Micromolecule additives such as lactic acid and citric acid,macromolecule additives including sodium carboxymethyl cellulose,fluorescent brighteners and phytohormone abscisic acid all had positive effect on cellulose production.6.95g/L of bacterial cellulose was obtained by NLQ127 under optimum conditions after 14d.The fermentation period can be shorten by improving the size and shape of containers.Using 1000mL triangle bottle in fermentation,a higher bacterial cellulose production of 7.13 g/L was obtained in7d.The bacterial cellulose was produced from wheat straw hydrolysate by 7d and the production reached 5.22 g/L.The bacterial cellulose produced by strain NLQ127 under different rotational speeds was characterized by fourier infrared spectroscopy,X ray diffraction,scanning electron microscopy,atomic force microscopy,thermogravimetric analyzer,and tension tester.SEM observation showed that there was no significant difference in length width ratio and density between fiber ribbons,and the average diameter was about 50-80 nm.With the increase of rotational speed,the arrangement of fibers became irregular and the bending fibers increased significantly.AFM showed that the surface of bacterial cellulose cellulose produced by dynamic fermentation was coarser,the length was micron scale and the aspect ratio was higher.The crystallinity of bacterial cellulose produced by static preparation reached 88.02%,which was higher than that of dynamically produced cellulose,and the ash content was the least.The moisture content of bacterial cellulose obtained from dynamic culture was higher than that from static culture.Thermogravimetric analysis showed that the thermal stability of dynamically produced bacterial fibers was improved.The mechanical property analysis showed that the rotational speed had a certain effect on the tensile strength of bacterial cellulose membrane.