Semi-scale Production of PHAs from Waste Frying Oil by Pseudomonas fluorescens S48

THE PRESENT study aimed at developing a strategy to improve the production of polyhydroxyalkanoates (PHAs) by Pseudomonas fluorescens S48 using waste frying oil (WFO) as the sole carbon source. Several cultivations were set up to steadily improve nutrients supply to attain high cell density and high biopolymer productivity. The production of PHAs was examined in a 14 l bioreactor as one-stage batch, two-stage batch, and high-cell-density fed-batch cultures. The highest value of polymer content in one-stage bioreactor was obtained after 60 h (33.7 %). Whereas, the two-stage batch culture increased the polymer content to 50.1 % after 54 h . High-cell-density (0.64 g/l) at continuous feeding rate 0.55 ml/l/h of WFO recorded the highest polymer content after 54 h (55.34 %). Semi-scale application (10 l working volume) increased the polymer content in one-stage batch, two-stage batch, and high cell density fed-batch cultures by about 12.3 %, 5.8 % and 11.3 %, respectively, as compared with that obtained previously by the authors in 2 l fermentation culture. Six different methods for biopolymer extraction were done to investigate their efficiency for optimum polymer recovery. The maximum efficiency of solvent recovery of PHAs was attained by chloroform– hypochlorite dispersion extraction. Gas chromatography (GC) analysis of biopolymer produced by Pseudomonas fluorescens S48 indicated that it solely composed of 3-hydroxybutyric acid (98.7%). A bioplastic film was prepared from the obtained PHB. The nucleotide sequence of the 16S rRNA gene of the studied isolate showed 98-99% similarity with Pseudomonas spp. particularly the Egyptian strain named Ps. fluorescens EG 639838