Thesis (M.Sc.) - Cairo University - Faculty of Agriculture - Department of Microbiology

PHAs (Polyhydroxyalkanoates) are considered an energy and carbon reserve that accumulatein bacteria. They are biodegradable substances easily be converted into CO2 and water within a year by a variety of microbes. The most widely studied PHAs are Polyhydroxybutyrate (PHB). This work was conducted to isolate PHB producing bacteria from seawater (the new Suez Canal, the city of Qantara, Ismailia, Egypt) and screening the isolates using Sudan Black B (SBB) and Nile blue A (NbA). A number of twenty isolates stained with SBB gave positive results (black- blue coloring), while sixteen of them were considered as PHB producers when using NbA dye. The identity of the selected isolates was identified based on their 16S rRNA gene sequencing and deposited in the GenBank. The effect of incubation temperature and aeration was studied to obtain high productivity of PHB. The results revealed that the use of 30{u00B0}C temperature with the use of aeration was more suitable for the production of PHB, where the highest productivity obtained 2.30 g /l when growing Bacillus megaterium strain YSBM6 at 30{u00B0}C and on a shaker incubator at 110 rpm for 48 h. To maximize PHB production by the most efficient strain YSBM6, different raw materials i.e. salted whey, molasses and mixture of them were examined as a carbon source instead of pure sucrose. Also nutritional (media type, sugar and salt concentration) and cultivation (pH, inoculum size, incubation temperature and time) parameters were optimized using one-factor-at-a-time method

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