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Production of dextran by some local isolates of bacteria
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Abstract: Dextran-a polymer of glucose- has many industrial and pharmaceutical uses. Up till now, there is a lack of studies concerning its production on large scale in Egypt. In view of that, the present study was designed to study dextran production by local isolates obtained from different dextran producing bacteria, nutritional and environmental factors affecting the production under laboratory conditions, use of some raw materials and by-products for large scale production, growth in fermentor as batch and continuous process as well as determination of physico-chemical properties of dextran.
A number of 63 dextran producing bacteria were isolated and identified as Leuconostoc (40 isolates) and Streptcoccus (23 isolates) strains. Of these, three Leuconostoc and two streptococcus were selected as high efficient strains. In a series of experiments, recommended medium for dextran production under lab conditions were found to contain 10% sucrose, 1% peptone and 0.5% yeast extract and 0.7% CaCO3, initial pH 6.7. Incubation for 48 h at 20 °C as a barch static culture provided high dextran productivity. Most efficient isolates were completely identified as Leuconostoc mesentroides strains.
Different molasses and sugar can juice failed to support dextran production by L. mesentroides strains. On the contrary, 2% corn steep liquor and 0.8% K2PO4 supported high dextran productivity and thus was selected as productive medium for production of dextran on large scale.
Biological activity of Lpcu 49 strain in the bioreactor under batch and continuous process were followed. All parameters determined showed the superiority of continuous over batch process. Dilution rate of 0.012 h-1 was recommended for dextran production, since it favoured higher viscosity and higher percentage of dextran production (2.22%).
Cell-free supernatant of fermented liquor in reservoir proved to be active in producing dextran from molasses when reaction mixture was incubated at 20 °C for 24 h. Dextran produced was white in colour and soluble in water. It contained 38.6% carbon, 0.465% nitrogen and 0.059% ash.
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| Publication year |
1998
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| Availability location |
كلية الزراعة جامعة عين شمس(معهد بحوث الاراضى والمياه والبيئة)
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| Availability number |
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| Organization Name |
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| Country |
Egypt
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| Department |
Agricultural Microbiology Research
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| Author(s) from ARC |
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| Agris Categories |
Agricultural research
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AGROVOC
TERMS |
Dextrans.
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| Proposed Agrovoc |
Dextran production;Bacterial polysaccharide ;Dextransucrase;Leuconostoc mesentroides;
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| Publication Type |
Master Thesis
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