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The effect of different levels of betaine and tryptophan on growth and resistance to salinities in the Caspian roach was investigated. Fish (1.90 ± 0.04 g body weight) were divided into 9 groups (4 treatments groups containing betaine (0.5 and 1), tryptophan (0.25 and 0.5), betaine and tryptophan mixtures (0.25- 0.5, 0.25, -1, 0.5-0.5 and 0.5- 1), and control group). After recording the growth factors, the fish were exposed to salinities (12, 16 and 20 ppt) and clinical symptoms and mortality rate were recorded. No mortality occurred in 12 ppt salinity. At 16 ppt, the lowest mortality (16.66%) was recorded in the treatment containing 1% betaine and 0.5% tryptophan, while the highest mortalty (59.98%) occurred in the control group. At 20 ppt salinity, 100% mortality occurred within 6 hours in the control, while in the other treatments 100%-mortality occurred after 24 hours. Behavioral symptoms, such as jerky movements, ataxia, increased respiratory rate, were more prominent in higher salinities. Tryptophan did not reduce food consumption meaningfully. Increaesd food consumption as the result of betaine did not show significant  effect on the fish growth rate.

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Sugar beet molasses is a well-known, inexpensive and available carbon source for microbial cell growth. Its sugar components are used to produce energy for microbial growth and non-sugar components, especially nitrogen components, have important roles in improvement of cell growth. On the other hand, immobilization of whole cell is establishment and physical limitation of intact cells in specific space that keeps their catalytic activity and provides the possibility of reuse of the cells. This technique allows continuous and accelerated biological processes. It also improves production efficiency and quality and simplifies recycling of product. Immobilized living cells, as controlled catalysts, are able to perform one-step enzymatic reaction and continuous fermentative processes. In this research, E.coli cells were immobilized in calcium alginate hydrogels and using sugar beet molasses as carbon source, were applied for tryptophan production reaction in the presence of its precursors, serine and indole. In comparison between free biocatalysts and immobilized bacterial cells that entrapped in alginate gels, indicated that larger amounts of amino acids (about 42/9%) can produce in calcium alginate. Also the production reaction was followed up for 9 sequential cycles, and results showed that the cells could produce tryptophan amino acid under above conditions. Use of sugar beet molasses (by-product of agriculture industries) for growth of microbial cells and tryptophan production, causes decrease in production cost and more economical production of tryptophan by immobilized E. coli.