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Abstract-The purpose of this research was to evaluate, the effect of incubation temperature and some substrates on exopolysaccharides (EPS) production. The S. thermophilus BN1 an EPS-producer strain isolated from cow milk was examined in this study. Skimmed milk, whole milk and cheese whey, were selected as culture media and two different temperatures were also tested. The EPS produced in the different studied conditions was purified and quantified. The strain BN1 was able to produce EPS in all established conditions. However, significant differences were observed in the amounts of produced EPS. The strain has been shown to produce high amounts of EPS at 37°C compared to 42°C (P<0.05). In skimmed milk at 37°C, the EPS amounts reached 548 PDM mg l-1, followed by 375 PDM mg l-1 and 325 PDM mg l-1 respectively in whey and whole milk. In addition, a slight significant difference was noted on the biomass, pH and lactic acid values obtained from the three fermented substrates (p <0.05). The present results demonstrate that suboptimal growth temperature (37°C) had a significant effect on the EPS production by S. thermophilus BN1.

The ability of Pseudomonas to grow and to produce siderophores is dependent on the iron content and the type of carbon sources in the medium. Under conditions of low-iron concentration the Pseudomonas isolates studied produced yellow-green fluorescent iron-binding peptide siderophores and the biosynthesis of this siderophores was affected by several different environmental parameters. Four basal media, supplemented with different concentration of iron, were employed to study the effect of iron and different organic carbon sources on siderophore production in Pseudomonas fluorescens. The highest siderophores concentration was obtained in succinate medium. Ferric iron increased the growth yield and completely repressed siderophores production above 200 g/l, but had a positive effect below 160 g/l. Penicillin and lead elicited the production of siderophores in the presence of excess iron. Pre-treatment of the standard succinate medium with α α α α,α α α α-dipyridyl and 8-hydroxyquinoline to reduce the concentration of iron diminished both the growth yield and siderophore production, but α α α α,α α α α-dipyridyl increased significantly the amount of siderophores produced in the presence of 0.20 mg/l of the chelating ion.

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