ABSTRACT:Bacterially produced polyhydroxybutyrate (PHB) polymer has a lot of potential as an application for environmentally degradable plastics. We aimed in this study to blend PHB with the semicrystalline polymers poly(vinyl acetate) (PVAc) and poly(vinyl acetate-co-vinyl alcohol) (PACA) to obtain material with better physical properties. We investigated compatibility over a wide composition range using different techniques. Viscosity measurements were used to study polymer-polymer miscibility in dilute solutions with chloroform as cosolvent. The data is discussed according to the viscosity interaction parameters, which are treated as excess properties by similarity with those of real solutions. Dielectric investigations were carried out at different frequencies ranging from 100 Hz to 50 kHz. The obtained data indicated that more than one relaxation mechanism was present, which were ascribed to the rotation of the main chain and its related motions. A glass-transition temperature composition diagram, IR spectroscopy, and a morphological investigation were also used to give more information about the compatibility of such blends. The results of this study indicate that PHB/PVAc is semicompatible, whereas PHB/PACA is compatible at least in the assayed composition range of hydrolysis. We also extended the study to carry out some biological activity investigations, which were tested against the representative number of pathogenic organisms with the disk diffusion method. The different compositions of the investigated blend were biologically active when compared with the individual polymers.
A suitable chemically defined culture medium was selected and some optimal conditions for the production of the highly immunosuppressive compound, cyclosporin A (Cyc A) are reported. Medium of the following composition was favorable for the production of Cyc A by Fusarium roseum: glucose, 30; NaNO 3 , 2; KH 2 PO 4 , 1; MgSO 4 .7H 2 O, 0.5 and KCL, 0.5 (g/l). Maximum productivity of Cyc A was achieved at pH 6.0 when 50 ml of the fermentation medium/250 ml flask, inoculated with five fungal agar discs (6 mm, diameter) of 7-days old F. roseum culture after incubation at 30 ºC at 120 rpm for 7 days.
Out of 210 actinomycetes isolates belonged to the genus Streptomyces recovered from rhizospheric soil of Triticum vulgaris, Zea mays and Vicia faba cultivated in Assuit and New Valley Governorates of Egypt, ten isolates were capable of producing high amounts of L-glutaminase enzyme. The most potent L-glutaminase producer isolate was Streptomyces sp. ASU319 recovered from rhizosphere of Triticum vulgaris. The higher producer actinomycete isolate was identified by sequencing of 16S rRNA as Streptomyces variabilis ASU319 and was deposited in the GenBank nucleotide sequence database under accession number KC145278. Factors affecting L-glutaminase production by the Streptomyces variabilis ASU319(KC145278) were examined and the results revealed that the maximum L-glutaminase value was obtained when the isolate cultivated in the production broth medium supplemented by glutamine 8 mg/ml, adjusted at pH 4 and incubated at 35 °C. These results suggest that L-glutaminase-producing Streptomyces variabilis ASU319 could be used as a plant growth promoting rhizobacteria by increasing the ammonia content in the rhizosphere soil across degradation of the agricultural wastes. Also this isolate can be used in both pharmaceutical and food industrial application for L-glutaminase production on commercial scale.
During the period from November 2009 to April 2010, 84 out of 560 extended spectrum β-lactamase (ESBL) producing negative bacteria were isolated from patients in different departments of the Ahmadi Hospital in Kuwait. The isolates were collected from urine catheter, wound, sputum, blood and other different samples. The ESBL infection rate in the in-patients was 62% and part of them (19%) were in the intensive care unit. All the isolated bacteria were identified and tested for antimicrobial susceptibility using an automated system (VITEK 2) and different antibiotic discs (15) by standard disc diffusion. The number of the recorded isolated multi-resistant Gram's negative bacteria was 54 isolates of Escherichia coli, 18 of Klebsiella pneumoniae, 11 of Pseudomonas aeruginosa, six of Proteus mirabilis, five of Enterobacter cloacae, four of Acinetobacter baumanii and one of Enterobacter aerogenes. They were resistant to the third generation of cephalosporins; Ceftazidime, Cefotaxime and Ceftriaxone. Meropenam (MEM) was the highest effective antibiotic against all the isolated bacteria (86%). The production of the ESBL was detected by phenotypic methods using E-test (96.4%), double disk synergy test (95%) and VITEK 2 (84.5%) in all multi-resistant isolates except A. baumanii and P. aeruginosa. All ESBL producing isolates were extracted and subjected to PCR using blaSHV, blaCTX-M and blaTEM primers. The bla-CTX-M (63.1%) was the most predominant ESBL gene that was produced in abundance by 42 isolates of E. coli. The most predominant ESBL isolates producing bla-TEM, bla-CTX-M and bla-SHV genes were successfully identified by 16 S rDNA. The conjugation assay between E. coli HB101 and the most predominant ESBL producing E. coli showed that the bla-CTX-M gene was able to be transferrable suggesting that they were plasmid mediated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.