الفهرس 
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Abstract
ABSTRACT
Different bacterial strains such as species of Gluconacetobacter formerly Acetobacter have been reported since 1886 to produce BC. Bacterial cellulose (BC) is very important exopolysaccharides with many applications in the pharmaceutical, textiles and paper Industries. The BC has better qualitative properties than plant cellulose. Therefore, this investigation was designed to study the production of BC by local bacterial strain.
In the present study, Thirty nine of cellulose producing bacteria were isolated from some rotten fruits and tested for cellulose production. One isolate was selected as high effect cellulose producing bacteria and completely identified as Komagataeibacter saccharivorans PE 5 through 16S ribosomal DNA sequencing, morphological, culture and biological characteristics. This isolate in addition to Acetobacter xylinum ATCC 10245(as a reference strain) were tested for cellulose production using static culture technique. In a series of experiments, two modifications in GAM medium were recommended to obtain the maximum growth and cellulose production by Komagataeibacter saccharivorans PE 5 and Acetobacter xylinum ATCC 10245 on the first and second modification media, respectively. Modified GAM medium No.1 contains (g/l) mannitol, 15; trypton ,6; ethanol 0.7% (v/v); acetic acid 0.2% (v/v); nicotinic acid, 0.0002 and CaCl2.2H2O, 0.1.Whereas the contains of modified GAM medium No.2 was (g/l) glucose, 15; yeast extract,3;peptone,3; ethanol 0.5%(v/v); acetic acid 0.3% (v/v); folic acid, 0.0004 and NaCl, 0.1. After optimization of culture condition including pH (3.5) and temperature (30 ºC).The cell growth and cellulose yield of Komagataeibacter saccharivorans PE 5 and Acetobacter xylinum ATCC 10245 on modified GMA media increased about 4.09 & 4.86 fold and 1.76 &1.39 fold, respectively than that recorded on GAM medium after 7 days static culture. Using agitated culture at 150 rpm led to decrease of cellulose production by these strains about 64% and 53% respectively. Modified GAM media supplemented with molasses as sole carbon source enhanced the bacterial cellulose yield which increased about 76.94% for Komagataeibacter saccharovorans PE 5 and about 28.40% for Acetobacter xylinum ATCC 10245 compared to control treatment.
The structure of BC produced from the two strains was studied by means of scanning electron microscope, fourier transform- infrared spectrum (FT-IR) and x-ray diffraction, as well as mechanical and optical prosperities of BC sheet produced. It was revealed the diameter of thin ribbons ranged from 34.34 nm to 39.16 nm and the shape of FT-IR curve for the two stains is similar to pure cellulose. The crystalinity index of A. xylinum ATCC 10245 is 54.14% and 52.76% for K.saccharivorans PE 5. Also, the properties of k.saccharivorans PE 5 cellulose increased about 1.19, 1.25, 1.33, 1.91 and 1.27 fold for wet tensile strength, dry tensile strength, degree of polymerization, brightness and opacity, respectively than A. xylinum ATCC 10245 cellulose.
Keywords. Bacterial Cellulose, A.xylinum, K.Saccharivorans, Molasses, Process Optimization, BC Sheet, Scan Electron Microscope (SEM), Fourier Transform Infrared (FT-IR), X-ray Diffraction (XRD).