BBIODEGRADABLE polyesters, polyhydroxyalkanoate (PHAs) are promising candidates for the development of environment-friendly and totally biodegradable plastics. The production of PHAs by Pseudomonas fluorescens S48 was examined using bioreactor as one-stage batch, two-stage batch, and fed-batch (pulsed, continuous and high cell density) cultures. Corn oil , soybean oil (extracted from their meal) and two types of waste frying oils (WFO) were used in the productive medium as a carbon source. The highest values of polymer content in the one-stage bioreactor fermentation (52 % and 76.53 %) were obtained after 60 h on media supplemented with extracted corn oil and soybean oil, respectively. Whereas, the highest figure obtained on WFO type 2 was 30 % under the same circumstances. Using bioreactor as a two-stage batch culture increased the polymer content with soybean, corn oil and WFO type 2 by 2.2 %, 32.11 % and 58 %, respectively as compared with that obtained in one-stage batch culture. High-cell-density (0.64 gl-1) at continuous feeding rate 0.55mll-1h-1 of WFO type 2 recorded the highest polymer content, yield and conversion coefficient after 48 h. Moreover, this application increased the polymer content by 65.7 % than that obtained in onestage batch culture as well as reduced the fermentation period 12 hr