الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Summary
The distinctive properties of cellulose as being renewable, biodegradable polymer with high strength, low density and high modulus, afforded it to be incorporated in many industrial applications. Most of the cellulose used in different industries is extracted from higher plants; some species of bacteria has the ability to produce cellulose which is called bacterial cellulose (BC). On the contrary to plant cellulose, BC is in pure form, has high crystallinity index, degree of polymerization, tensile strength, water holding capacity and being nontoxic, so it has been used in medical, textiles and cosmetics applications.
The high costs of substrates used in production of BC and the low yield of the produced cellulose are considered great obstacles that hinder its utilization on an industrial scale. Replacing these substrates with industrial by-products receive the attention of researchers as they decrease the production costs, enhance the production process because of the valuable components of these by-products including nitrogen and carbohydrates as well as vitamins and mineral salts.
Kombucha tea is the fermented drink that resulted from the fermentation of a sugared black or green tea with a precultured tea fungus sample that is an association of bacteria and yeast for 7-14 days producing many acids and ethanol as the main metabolic products and a new daughter tea fungus layer (BC) is produced on the surface of the tea medium.
The present study aimed to utilize the available industrial by-products as an inexpensive carbon and nitrogen sources for BC production by Kombucha tea fungus. Crude and acid treated molasses, black liquor and acid whey are considered the alternative carbon sources instead of sucrose while corn steep liquor is the suggested alternative nitrogen source instead of black tea in black tea media. The produced cellulose was coded as the kombucha bacterial cellulose (KBC). Estimation of the yield and productivity of the KBC produced from the alternative media are compared to those obtained from the synthetic media (black tea medium). The bacterial strains found in tea fungus, which are responsible for producing cellulose, are isolated and identified by different biochemical tests and by 16SrRNA. The bacterial isolates were inoculated in the media of the highest KBC yield to evaluate their efficiency to produce BC. Paper sheets obtained from KBC and BC, by pressing and drying, were characterized to detect their morphological and mechanical characteristics using scanning electron microscopy (SEM) and tensile strength respectively. Also, the structural characteristics were analyzed using Fourier transform infra-red, x-ray diffraction (XRD) and degree of polymerization (DP).
The results are summarized as follow:
1. Production of KBC using 10% crude molasses (CM) as alternate carbon source with different nitrogen sources as black tea, green tea, yeast extract and peptone in static conditions at 30oC in the duration of 14 days was studied. The highest yield being 3.58 g/L was obtained in CMY medium.
2. The treatment of molasses with 1N H2SO4, HCL or HNO3 to remove its harmful components and testing the efficiency of the resultant treated molasses at concentration 10% with 1% of black tea as nitrogen source for producing KBC in the optimum conditions was investigated. It was found that treated molasses with 1N H2SO4 gave the highest yield of KBC (7.9 g/L).
3. 1N H2SO4 treated molasses (10%) was tested with many nitrogen sources as black tea, green tea, yeast extract and peptone in the culture media used for the production of KBC in the optimum conditions. The maximum yield (9.74 g/L) was obtained in TMY medium.
4. After removal of impurities containing nitrogen, AW as a carbon source was used with black tea, green tea, yeast extract and peptone as nitrogen sources for KBC production for 14 days at 30oC. The highest yield was that of AWY medium being (8.16 g/L).
5. After removal of lignin from the black liquor by acidification and precipitation, it was tested in concentration 10% with synthetic nitrogen sources as black tea, green tea, yeast extract and peptone for producing KBC in the optimum conditions. The highest yield was 0.83 g/L obtained in BLY medium.
6. Corn steep liquor was tested as alternate nitrogen source in the concentration 1% with different synthetic carbon sources as glucose, sucrose and fructose to detect its ability to produce KBC in the optimum conditions. The maximum yield was (7.92 g/L) in FCSL medium.
7. Among all the by-products used as a nutrient medium, AW gave a considerable KBC yield (4 g/L) with respect to the others.
8. The efficiency of producing KBC in the optimum conditions was tested by using 1% corn steep liquor as nitrogen source with 10% crude molasses or 1N H2SO4 treated molasses or black liquor or acid whey as carbon sources. The highest yield was 11.72 g/L produced in TMCSL medium followed by 8.5 g/L that obtained in AWCSL medium.
9. Different ratios of the by- products used as carbon sources were mixed giving the final concentration 10% and tested with 1% CSL for the production of KBC in the optimum conditions. The highest yield was recorded for the ratio 9:1 of TM: AW, TM: BL, AW: BL, AW: CM and CM: BL mixture with 1% CSL giving 9.56, 6.1, 5.14, 5.76 and 2.16 g/L of KBC yield respectively.
10. Different types of media (HS, Glucose ethanol, Watanabe and Yamanaka and Gluconobacter oxydans medium) were used to isolate the bacteria responsible for production of BC from kombucha tea fungus and two different bacterial isolates were detected.
11. The isolated bacteria were identified morphologically, characterized by many biochemical tests and the results were compared to Bergey,s manual systematic which revealed that the first one was belonging to the Acetobacter while the second one belonged to Gluconobacter.
12. The two isolates were identified using 16S rRNA, the first strain showed homology with the strain Acetobacter pasteurianus while the second one showed homology with Gluconobacter oxydans.
13. TMCSL medium, of the highest KBC yield, was chosen to produce BC by Acetobacter pasteurianus and Gluconobacter oxydans strains in the optimum conditions.
14. KBC and BC obtained from TMCSL medium as well as those produced from the reference one (black tea) were purified, pressed and dried to produce paper sheets then tested to estimate their morphological, structural and mechanical characteristics.
a- FTIR data and XRD patterns approved that all the obtained KBC and BC sheets are similar to pure cellulose. The crystallinity index values of SBT, TMCSL and AWCSL media were 80.2%, 84.4% and 81.9%, respectively, while that produced by Acetobacter pasteurianus and Gluconobacter oxydans was 89% and 91%, respectively.
b- SEM micrographs indicated the three dimensional ultrafine network structure of all samples where the width of ribbons ranged from 29 to 62 nm.
c- The tensile strength values of the BC paper sheets produced by Acetobacter pasteurianus and Gluconobacter oxydans were 96.72 MPa, 95.72 MPa respectively, while those of the KBC paper sheets produced in SBT, TMCSL and AWCSL media was 77.52MPa, 53.91MPa and 75.52 MPa.
d- The degree of polymerization values of bacterial cellulose produced by Acetobacter pasteurianus and Gluconobacter oxydans were 2597, 2714 respectively which are slightly higher than those obtained in the KBC samples produced in SBT, TMCSL and AWCSL media (2328, 2186 and 2430) respectively