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The present study aimed at developing a strategy to improve the volumetric production of PHAs by Pseudomonas fluorescens S48 using waste frying oil (WFO) as the sole carbon source. For this purpose, 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 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 PHA 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-hydrobutyric acid (98.7%). A bioplastic film was prepared from the obtained PHB. The isolate studied shares the same identical sequence, which is nearly the complete 16S rRNA gene. The identity of this sequence to the closest pseudomonads strains is about 98–99%. It was probably closely related to support another meaningful parsiomony analysis and construction of a phylogenetic tree. The isolate is so close to Egyptian strain named EG 639838.

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Soil samples were collected from different rhizosphere plants grown in SEKEM farm, Bilbis, El-Sharkyia governorate, Egypt. Four fluorescent pseudomonads isolates, out of seventy one, were selected according to their efficiency to produce IAA, cyanide, antagonistic effect and high ability to solubilize potassium and phosphorus. These isolates were identified using 16S rRNA gene sequencing technique to be different strains of Pseudomonas otitidis. Growth curve and growth kinetics were determined on king's broth medium. Ps. otitidis SE8 gave the highest specific growth rate, multiplication rate and number of generation being 0.287 h À1 , 0.4147 h À1 and 4.98 h À1 , respectively. This strain also showed the lowest of doubling time. Ps. otitidis SE8 and OL2 had higher activity to solubilize phosphorus than other tested strains. Bacterial strain SE8 also gave a considerable amount of soluble potassium as compared with other strains being 80.7 ppm. The maximum IAA and gibberellic acid production was also recorded by Pseudomonas SE8 and OL2. A remarkable quantity of siderophores was detected in the case of Ps. otitidis SE8 being 28.20 mM DFOM. Application of these isolates as inoculants for tomato plants in green house was performed. The results showed that inoculation of tomato seedling with Pseudomonas strains led to suppress the soil-borne pathogen, increased of NPK uptake and supported tomato plant growth. ª 2015 Production and hosting by Elsevier B.V. on behalf of Faculty of Agriculture, Ain Shams University.

Growth promotion and disease control by rhizobacteria are complex interrelated processes that involve direct and indirect mechanisms. The mechanisms include synthesis of some metabolites (auxin, cytokinin and gibberellins), induction of 1-aminocyclopropane-1-carboxylate (ACC) deaminase, production of siderophore, antibiotics, hydrogen cyanide hydrogen cyanide (HCN) and volatile compounds. They also include mineral solubilization competition, and induction of systemic resistance. These bacteria are suitable as soil inoculants because they have the potential for rapid and aggressive colonization. This feature alone is characterised as a disease control mechanism, which prevents the invasion of detrimental soil microorganisms onto the root surface. Inoculant-based plant growthpromoting rhizobacteria (PGPR) is applied extensively on agricultural crops to improve plants' growth and simultaneously reduce chemical inputs like fertilizer and pesticide which can cause environmental degradation. The structure of the rhizobacterial community is affected by several factors including plant genotype and is determined by the amount and composition of root exudates. In addition, soil type and fertility are the contributing factors that shape the community. This form of communication can affect plants' growth, nutrient status and also susceptibility to stress and pathogens in the host plant. PGPR inoculants cause diverse beneficial interactions among plants, which leads to sustainable and environment-friendly agriculture. The application of rhizosphere soil of agricultural crops with desirable bacterial populations is considered promising in both laboratory and greenhouse experiment. Further, a clearer understanding of the way PGPRs promote plants' growth can lead to expanded exploitation of these 'biofertilizers' in order to reduce the potential negative environmental effects associated with food and fiber production.

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The ability of microorganisms to reduce inorganic metals has launched an exciting eco-friendly approach towards developing green nanotechnology. Thus, the synthesis of metal nanoparticles through a biological approach is an important aspect of current nanotechnology. In this study, Streptomyces aizuneusis ATCC 14921 gave the small particle of silver nanoparticles (AgNPs) a size of 38.45 nm, with 1.342 optical density. AgNPs produced by Streptomyces aizuneusis were characterized by means of UV-VIS spectroscopy and transmission electron microscopy (TEM). The UV-Vis spectrum of the aqueous solution containing silver ion showed a peak between 410 to 430. Moreover, the majority of nanoparticles were found to be a spherical shape with variables between 11 to 42 nm, as seen under TEM. The purity of extracted AgNPs was investigated by energy dispersive X-ray analysis (EDXA), and the identification of the possible biomolecules responsible for the reduction of Ag+ ions by the cell filtrate was carried out by Fourier Transform Infrared spectrum (FTIR). High antimicrobial activities were observed by AgNPs at a low concentration of 0.01 ppm, however, no deleterious effect of AgNPs was observed on the development and occurrence of Drosophila melanogaster phenotype. The highest reduction in the viability of the human lung carcinoma and normal cells was attained at 0.2 AgNPs ppm.