Fermentation and oxygen transfer characteristics in recombinant human growth hormone production by Pichia pastoris in sorbitol batch and methanol fed‐batch operation

BACKGROUND: The influence of methanol feed rate on recombinant human growth hormone (rhGH) production by Pichia pastoris hGH‐Mut⁺ in medium containing sorbitol was investigated at three different specific growth rates (µ), namely, 0.02 (MS‐0.02), 0.03 (MS‐0.03), and 0.04 (MS‐0.04). RESULTS: Increasing methanol feed rate above MS‐0.03 did not affect sorbitol consumption, showing that µ = 0.03 h^?1 is a threshold limiting value, above which sorbitol utilization became independent of methanol feed rate. Moreover, when sorbitol was consumed, no further cell growth was observed. Increase in methanol feed rate triggered cell synthesis and the highest cell concentration was obtained at MS‐0.04 as 48 g L^?1 (t = 18 h); whereas, the highest rhGH production, 270 mg L^?1, was obtained at MS‐0.03 as a consequence of lower extracellular protease production and higher AOX activity (41 U g^?1 CDW). Oxygen uptake rate increased with increasing µ, having the maximum value, 76.6 mmol m^?3 s^?1, at MS‐0.04. K_La had a tendency to increase with µ, having a maximum value of 0.15 s^?1 at MS‐0.04 (t = 15 h). CONCLUSION: By considering rhGH concentration and oxygen transfer characteristics, the bioprocess can be improved by a two‐stage feeding strategy, operating at MS‐0.04 at the beginning of fermentation, and thereafter shifting to MS‐0.03. Copyright © 2009 Society of Chemical Industry     

Metals (major,essential to non-essential) composition of the different tissues of three demersal fish species from İskenderun Bay,Turkey

This study was performed to investigate certain major and toxic metal concentrations in different tissues of three demersal fish species (Triglia lucerna, Lophius budegassa, Solea lascaris). Generally, skin and liver exhibited higher metal concentrations than did muscle. Sodium and arsenic concentrations were found at higher levels in muscle tissues than in livers and skin, while zinc and nickel in different organs were classified as follows: skin > liver > muscle tissues. The concentrations of trace metals in fish samples indicated that S. lascaris was more contaminated than were other fish species, followed by L. budegassa and T. lucerna. It may be concluded that consumption of these species from this region is not likely to pose a threat for human health. However, although the concentrations are below the limit values for fish muscles, a potential danger may emerge in the future, depending on domestic waste waters and industrial activities in the region. Therefore, further monitoring programmes should be conducted.     

Thermal and mechanical properties of polypropylene nanocomposite materials reinforced with cellulose nano whiskers

We use polypropylene (PP, an apolar polymer) and cellulose nano whiskers (CNW, a polar material) to produce nano polymer composites with enhanced mechanical and thermal properties. To improve compatibility, maleic anhydride grafted PP has also been used as a coupling agent. To enhance the uniform distribution of CNW in the composite, the matrix polymer is dissolved in toluene, and sonification and magnetic stirring are applied. Good film transparency indicates uniform CNW dispersion, but CNW domains in the composite film observed under an scanning electron microscope may indicate slight agglomeration of CNW in the composite film. The tensile strength of the composite compared with neat PP improves by 70–80% with the addition of CNW. The crystallinity has also been improved by about 50% in the CNW reinforced samples. As the content of CNW increases, the composite exhibits higher thermal degradation temperature, higher hydrophilicity, and higher thermal conductivity. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

An Efficient Algorithm for the Single Machine Total Tardiness Problem

This paper presents an exact algorithm for the single machine total tardiness problem (1// Σ T_i). We present a new synthesis of various results from the literature which leads to a compact and concise representation of job precedences, a simple optimality check, new decomposition theory, a new lower bound, and a check for presolved subproblems. These are integrated through the use of an equivalence concept that permits a continuous reformation of the data to permit early detection of optimality at the nodes of an enumeration tree. The overall effect is a significant reduction in the size of the search tree, CPU times, and storage requirements. The algorithm is capable of handling much larger problems (e.g., 500 jobs) than its predecessors in the literature (≤ 150). In addition, a simple modification of the algorithm gives a new heuristic which significantly outperforms the best known heuristics in the literature.     

A force analogy method (FAM) assessment on different static condensation procedures for frames with full Rayleigh damping

In this paper, influence of different static condensation methods on nonlinear time history response of structures in presence of full Rayleigh damping matrix has been studied. Equation of motion is derived in details for 2 newly introduced cases; Full Static Condensation Model and Reduced Static Condensation Model (RSCM or RSCM‐1). Nonlinear analyses are performed with state‐space form of equation of motion along with force analogy method. A novel aspect of this study in comparison with previous researches is to consider full Rayleigh damping in formulations for static condensation in nonlinear structural analysis. Numerical examples are presented for the proposed methods. In addition, the same structure was modeled in finite element method and analyzed by the OpenSEES program. Comparisons demonstrate that results, which are obtained from introduced methods in this article, are in good agreement with the finite element method results. In addition to explaining the equation derivations in main article, proofs for some equations have been demonstrated in appendices. The comparisons show that both RSCM and Full Static Condensation Model lead to almost the same results but in case of using RSCM‐1, the responses have some deviation from other condensation methods.     

Influences of sex and seasons on levels of heavy metals in tissues of green tiger shrimp (Penaeus semisulcatus de Hann, 1844)

Seasonal changes in heavy metal (Ag, Cr, Ni, Pb, Cu, Fe, Zn) concentrations in muscle, gill, hepatopancreas and gonad tissues of both male and female green tiger shrimp (Penaeus semisulcatus) from Iskenderun Bay (Northern East Mediterranean Sea, Turkey) were measured for a year period by using ICP-AES. The relationships in various heavy metal concentrations in organs were compared according to sex and seasons. Heavy metal content varied with type of metals, seasons and sex. Accumulations also differed significantly in certain organs. Metal concentrations (as μg g⁻¹ w.w.) were highest in male gonads whereas lowest in the muscle of all shrimp species. From the human consumption point of view, heavy metal concentrations except for copper in male and female green tiger shrimp’s muscle were below the admissible limits. Thus, precautions should be taken on account of higher content of heavy metals as well as in other organs that could be affected by industrial pollution.     

COUPLED THERMOELASTICITY OF A LAYERED MEDIUM

The transfer matrix method recently developed by the authors is applied to a layered medium. The components of the state vector are taken as the temperature, the displacement, the heat flux, and the strain. Interface conditions are automatically satisfied by multiplying the initial state vector by a layer matrix, and then by a point matrix that accounts for the finite discontinuity of the strain across the interface. The missing components of the initial state vector are determined from the corresponding boundary conditions. Global and local response is then determined by continued matrix multiplication.     

STATE SPACE AFPROACH TO THERMOELASTICITY

The method of the matrix exponential, which constitutes the basis of the state space approach of modern control theory, is applied to the nondimensional equations of coupled thermoelasticity. The disadvantages of using the thermoelastic potential are thus avoided. The results obtained can be used to generate solutions in the Laplace-transform domain to a broad class of problems in thermoelasticity. Applications to problems pertaining to a half-space and a layer are presented.     

Unilateral digital clubbing in a hemodialysis patient

We present an unusual case of a chronic hemodialysis patient with moderate diffuse acrocyanosis and prominent unilateral clubbing of his right hand fingers, with classic physical features of hypertrophic osteoarthropathy. The patient's left hand, which had a functioning arteriovenous fistula, did not show any evidence of clubbing. We briefly discuss the different theories in regards to the pathogenesis of clubbing, and the potential role of arteriovenous fistula in preventing its occurrence.