الفهرس 
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Abstract
Egypt produce about 5.65 million tons of dairy products and manufacturing about 644 thousand tons of cheese/ year. While, whey production may reach to 1,200 tons daily. It is considered as a very problematic byproduct of cheese making in milk and dairy factories, especially in traditional dairy MSMEs (Micro, Small and Medium Enterprises) in rural areas, where they perform no waste-water treatment to mitigate the negative environmental impact of discarded whey.
In most cases, traditional cheese manufacturers discard whey directly to the sewage drain. Or, in villages lacking public drainage, the whey seeps into the soil, since the cost of drainage by private trucks is very high. So, it needed to develop new methods to derivate new products from whey, especially “salted” whey, a byproduct of processing Domiati cheese.
Bacterial exopolysaccharides (EPS) plays a key role in changing the physical properties of foodstuffs, making it suitable for use as thickening, moistening or stabilizing agents in the food industry. A balance between carbon and nitrogen sources is necessary to obtain a high EPS concentration, but other factors such as growth temperature, pH and agitation affect EPS production. Using cheese whey and milk permeate as a fermentation media present the opportunity to create value-added EPSs.
Thus, present work was planned to study the use of some isolated halophilic bacteria to produce exopolysaccharides by fermentation process from salty cheese whey and milk permeate.
Part I: Isolation and Identification of Halophilic Bacteria Producing Exopolysaccharides
The obtained results could be summarized as follows:
• Forty-six isolates were isolated from dairy samples and water samples, seven isolates produced EPS from salty cheese whey and milk permeate.
• The isolates could be growing in range of 0-20% NaCl, with optimum concentration 10%, while the optimum pH was 7, and 37°C for the optimum temperature to produce the maximum yield of EPSs.
• The maximum yield of EPS was obtained by three isolates which identified by Biolog system and 16 sRNA.
• Identified strains were one strain of Alteribacillus bidgolensis and two strains of Bacillus licheniformis.
Part II: Improvement the production of exopolysaccharides from salty cheese whey and salty milk permeate and its characterization
• Addition of ammonium sulphate was more effective than urea on EPS production from selected strains.
• The highest yield of EPS was 5.41 g/l obtained when the ammonium sulphate concentration was 0.2%. for strain 16. where it was 3.85 g/l when ammonium sulphate concentration was 0.6% for strain 37. But in strain 41 the highest yield was of 4.83 g/l obtained when the ammonium sulphate concentration was 0.4%.
• The highest yield was 5.11 g/l, 3.88 g/l and 4.53 obtained when the urea concentration was 0.2%, for strains 16, 37 and 41 respectively.
• Melting point of the exopolysaccharide was evaluated by DSC, the EPS of Alteribacillus bidgolensis (isolate no. 16) showed different thermal properties than the EPS produced by Bacillus licheniformis (isolate no. 37 and 41). The endothermic peak started at 198.5°C, 209.7°C and 189.9°C for the three isolated tested strains respectively.
• The structure of isolated EPS selected strains Alteribacillus bidgolensis (isolate no. 16) and from Bacillus licheniformis (isolate no. 37 and 41) were analyzed by HPLC and we found that almost EPSs consist of the glucose monomer (73.1, 65.1 and 60.4% respectively) with some traces of another sugars.
Part Ⅲ: Effect of the isolated EPSs on Rheological and Physicochemical Properties of Yoghurt
• Lactic acid bacteria counts declined but counts were still >107 cfu/mL at the end of the storage for control and all the treatments of yoghurt, although there is no count observed for yeast and molds or total coliform during the storage period.
• A gradual decrease in pH value could be observed with extending the cold storage period and increasing in acidity of yoghurt during the storage period. Although there is no significant different in total solids, ash, and total nitrogen during storage periods. With increasing in soluble nitrogen.
• Additions of exopolysaccharides to yoghurt are effective in absorbing water, increasing viscosity, strengthening and improving the texture of yoghurt. It also maintains the morphological features of yoghurt during transportation and storage. These characteristics was evaluated by texture analyzers.
• Exopolysaccharide could improve the quality of yogurt, while having no effect on flavor of yogurt. Therefore, it could replace some commercial stabilizer.
In conclusion, the study recommends that use of both Alteribacillus bidgolensis and Bacillus licheniformis in the production of exopolysaccharides (EPSs) from whey containing high salt concentrations to increase the economic benefits, and to contribute in solving environmental pollution problems resulting from not using it and disposing it in ways that are not environmentally safe.