Kinetic model for polyhydroxybutyrate (PHB) production by Hydrogenophaga pseudoflava and verification of growth conditions

A kinetic model that describes microbial growth, biopolymer production and substrate consumption is used to predict the performance of batch fermentation of Hydrogenophaga pseudoflava. H. pseudoflava DSMZ 1034 is useful in synthesizing polyhydroxyalkanoates (PHAs).The experimental data was also fitted with the logistic equation that can provide adequate description for PHA synthesized by H. pseudoflava. The Lineweaver-Burk plot defined biokinetic coefficients which were described by a simplified Monod’s rate model. The specific growth rates, max and the Monod constants, Ks, for various substrates such as glucose, fructose were 0.36, 0.24, h-1 and 106, 80 g/l, respectively. A good agreement was found between the experimental and the predicted values, which indicated that the model with differential equations would describe fermentation process for the PHA formation

Theoretical study of fMet-tRNA and fAla-tRNA structures by using quantum calculation

AbstractIn the prokaryotes, protein synthesis always starts with N-formylmethionine amino acid. Comparison of this amino acid with other amino acids is attempted and that is why formylmethionine is always the first amino acid to begin protein synthesis, in this paper we added a formyl group to alanine amino acid and then studied it when attached to the tRNA molecule and compared this structure with formylmethionine-tRNA structure. The quantum chemical calculations have performed using Gaussian 03 suite of programs. The fAla-tRNA and fMet-tRNA structures have fully optimized at the HF and B3LYP levels with 3–21G∗ and 6–31G∗ basis sets as well as MP2/3–21G∗ level and theoretically solvent effects on the structures were investigated. Then we studied electronic structures of the compounds using Natural Bond Orbital (NBO) analysis and calculated NMR parameters at the gas-phase. Frequency analysis was also calculated at the HF and B3LYP/3-21G∗ levels in the different solvents in 298.15K, 310.15K temperatures and 1.00 atmosphere pressure

A kinetic model for citric acid production from apple pomac by Aspergillus niger

The fermentation kinetics of citric acid by Aspergillus niger were studied in a batch system. A simple model was proposed using the logistic equation for growth, the Luedeking-Piret equation for citric acid production and Luedeking-Piret-like equation for glucose consumption. The model appeared to provide a reasonable description for each parameter during the growth phase. The production of citric acid by A. niger is growth-associated

Adopting flexibility of the end-plate connections in steel moment frames

The majority of connections in moment resisting frames are considered as being fully-rigid. Consequently, the real behavior of the connection, which has some level of flexibility, is ignored. This may result in inaccurate predictions of structural response. This study investigates the influence of flexibility of the extended end-plate connections in the steel moment frames. This is done at two levels. First, the actual microbehavior of extended end-plate moment connections is explored with respect to joint flexibility. Then, the macro-behavior of frames with end-plate moment connections is investigated using modal, nonlinear static pushover and incremental dynamic analyses. In all models, the P-Delta effects along with material and geometrical nonlinearities were included in the analyses. Results revealed considerable difference between the behavior of the structural frame with connections modeled as fully-rigid and those when flexibility was incorporated regarding to natural periods, strength and maximum inter-story drift angle

GROWTH KINETIC PARAMETERS AND BIOSYNTHESIS OF POLYHYDROXY-BUTYRATE IN Cupriavidus necator DSMZ 545 ON SELECTED SUBSTRATES

A kinetic model for Cupriavidus necator in batch culture using glucose, fructose and molasses as carbon sources was obtained. The experimental data was also fitted with the modified logistic equation that can provide adequate description for PHB synthesized by C. necator. The Lineweaver-Burk plot defined biokinetic coefficients which were described by a simplified Monod’s rate model. The specific growth rates, μmax and the Monod constants, Ks, for various substrates such as glucose, fructose and molasses were 0.18, 1.25, 0.42 h-1 and 107.53, 30.342 and 188.16 g/l, respectively. The kinetic constants were evaluated on the basis of non-linear regression solved using MATLAB soft¬ware. Good agreement was found between the experimental and the predicted values, which indicated that the model with differential equations would describe fermentation process for the PHB formation

Minimum inhibitory concentration of silver nanoparticle against Staphylococcus aureus and its relation with Methicillin resistance and bacterial source of isolation

Background and Objective: The rise of antibiotic resistance particulary Methicillin resistance in pathogenic bacteria such as Staphylococcus aureus is found to be an emerging threat to human health especially in hospitals. Heavy metal nanoparticles such as Ag used for inhibition of this bacterium. This study was done to determine of minimum inhibitory concentration (MIC) Ag nanoparticle against Staphylococcus aureus which isolated in Gorgan, north of Iran and its relation with Methicillin resistance and source of bacteria. Methods: In this descriptive – analytical study, the MIC Ag nanoparticle in 183 isolates of Staphylococcus aureus by microdilution method was determined. 30 isolates, based on mecA gene was considered as MRSA. Samples were collected from patients, nose of healthy carriers and foods. Compare the MIC of isolates based on Methicillin resistance, source of the bacteria and resistance to other antibiotics were assessed. Results: Out of 183 samples MIC was varied from 1 to 16 µg/ml, and mean±std was 2.9±1.89 µg/ml. MIC mean of silver nanoparticles in isolated from foods were 2±0.7, isolared from healthy carriers were 4.1±2.4 and from patients were 3.4±2.1 µg/ml and were statically significant (P<0.05). MIC mean of silver nanoparticles in MSSA isolates are 3.9±2.3 and in MRSA isolates are 2.4±1.4 µg/ml that were statically significant (P<0.05). MIC mean of gentamycin resistant isolate were lower than sensitive one. But between MIC of silver nanoparticles and other antibiotics resistance was not significant statistically. Conclusion: There is a relation between silver nanoparticle MIC, source of sample isolation, Methicillin and gentamycin resistance. Since MIC of silver nanoparticles on isolates of Methicillin resistant is low, the possibility of its use in the control of MRSA in hospital infections can be considered as a prime attention the Gentamycine

Influence of the adsorption of toxic agents on the optical and electronic properties of B12N12fullerene in the presence and absence of an external electric field

The interaction energies and optoelectronic properties, in the presence and absence of an electric field, have been studied for the interaction of B12N12 with the toxic agents sarin (SF) and chlorosarin (SC) using density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. The results demonstrate that the PO group of SF and SC molecules can adsorb on the B12N12 with binding energies of -0.75 and -0.79 eV for the PBE functional, respectively. However, the binding energy of SC on B12N12 is slightly higher than that of SF. It was found that the electric field in the +Y direction increases the binding energies of the SF and SC molecules, while the electric field in the +X direction decreases the adsorption energy. Our computational results show the capability of B12N12 fullerene as a sensor for potential applications in the detection of toxic agents (SF and SC) under an external electric field. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique