Optimizing cropping pattern to improve the performance of irrigation network using system dynamics-Powell algorithm.

One of the strategies for agricultural development is the optimal use of irrigation and drainage networks, which leads to higher productivity and economic benefits. In this regard, quantitative and qualitative studies of drainage water from networks are essential for efficient water management. In the present study, we develop a model using a system dynamics approach to simulate the cropping pattern of an irrigation and drainage network as well as the discharge and salinity of drainage water from network farms. We apply the Powell algorithm to optimize the economic profitability of cultivated crops by considering the salinity and discharge of drainage water from the fields. With three aims, i.e., (1) maximizing benefit-cost ratio, (2) minimizing drainage water salinity and discharge of network, and (3) economic and environmental considerations simultaneously, the optimization of cropping pattern within the Kosar irrigation and drainage network is performed. Results based on five consecutive years under different scenarios showed that some crops, such as watermelon, are not economically recommened for production due to high costs, water consumption, and low selling price causes environmental pollution. On the other hand, wheat, grain maize, silage maize, sorghum, and alfalfa have different conditions, and their production is suitable by considering all scenarios. By comparing with experimental data, we find that the proposed model is accurate to simulate and optimize the irrigation network and to detect its cropping pattern.

Bioprocess and downstream optimization of recombinant human growth hormone in Pichia pastoris.

The methylotrophic yeast Pichia pastoris is a well-established expression host, which is often used in the production of protein pharmaceuticals. This work aimed to evaluate the effect of various concentrations of ascorbic acid in mixed feeding strategy with sorbitol/methanol on productivity of recombinant human growth hormone (r-hGH). The relevant concentration of ascorbic acid (5, 10, or 20 mmol) and 50 g/L sorbitol were added in batch-wise mode to the medium at the beginning of induction phase. The rate of methanol addition was increased stepwise during the first 12 h of production and then kept constant. Total protein and r-hGH concentrations were analyzed and the results compared with sorbitol/methanol feeding using one-way analysis of variance. Moreover, an effective clarification process using activated carbon was developed to remove process contaminants like pigments and endotoxins. Finally, a three-step chromatographic process was applied to purify the product. According to the obtained results, addition of 10 mmol ascorbic acid to sorbitol/methanol co-feeding could significantly increase cell biomass (1.7 fold), total protein (1.14 fold), and r-hGH concentration (1.43 fold). One percent activated carbon could significantly decrease pigments and endotoxins without any significant changes in r-hGH assay. The result of the study concluded that ascorbic acid in combination with sorbitol could effectively enhance the productivity of r-hGH. This study also demonstrated that activated carbon clarification is a simple method for efficient removal of endotoxin and pigment in production of recombinant protein in the yeast expression system.

Evaluation of Sorbitol-Methanol Co-Feeding Strategy on Production of Recombinant Human Growth Hormone in Pichia Pastoris.

Recombinant protein production in Pichia pastoris is based on alcohol oxidase promoters which are regulated by methanol. However, the use of methanol has several disadvantages, which is why current trends in bioprocess development with Pichia pastoris (P. pastoris) are focusing on methanol mixed feeding strategies. This work aimed to develop a new experimental method and compare the effect of various fractions of sorbitol in mixed feeding strategy with stepwise addition of methanol to maximize the productivity of human growth hormone. Accordingly, fed-batch culture performed with a mixed feed of sorbitol/methanol. Sorbitol at concentrations of 30, 40, 50 and 60 gram per liter was added in batch-wise mode to the medium at the beginning of induction phase and the rate of methanol addition was increased stepwise during the first 12 h of production and then kept constant. In order to understand the effects of various co-substrate feeding strategies on P. pastoris and its production of hGH, cell mass, dry cell weight, total protein, hGH expression level and hGH concentration were analyzed and the results compared with the basic feeding protocol using one-way analysis of variance (ANOVA). According to the obtained results, sorbitol at a concentration of 50 g/L could significantly increase the production yield. Under such optimal conditions cell biomass was 108 g/L (DCW), total protein was 0.807 g/L, expression level was 83.1% and rhGH concentration was 0.667 g/L following 30 h induction.

Evaluation of thimerosal removal on immunogenicity of aluminum salts adjuvanted recombinant hepatitis B vaccine.

Thimerosal, which is approximately 50% mercury by weight is a preservative widely used in vaccines since the 1930's. It meets the requirements for a preservative as set forth by Pharmacopeia challenge test and has been shown to be effective against a broad spectrum of pathogens. In July 1999, the Public Health Service agencies and vaccine manufacturers agreed that thimerosal should be reduced or eliminated in vaccines as a precautionary measure but, due to the lack of appropriate alternative, it is still extensively used in multiple dose formulations of vaccines such as hepatitis-B in developing countries. In this study the effect of the removal of thimerosal in two formulations of hepatitis B vaccines containing either aluminum hydroxide or aluminum phosphate were evaluated in Balb/c mice. These formulations were administered interperitoneally and the titer of antibody was determined by ELISA technique after 28 days. The geometric mean of antibody titer (GMT), seroconversion and seroprotection rates, ED50 and relative potency of different formulations were determined. The ED50 of thimerosal-free formulations were reduced by more than 35% in both preparations. In addition, GMT of antibody titer, seroconversion and seroprotection indicated significantly higher immunogenicity for thimerosal free formulations for both aluminum phosphate and hydroxide adjuvants.

Biological activity analysis of native and recombinant streptokinase using clot lysis and chromogenic substrate assay.

DETERMINATION OF STREPTOKINASE ACTIVITY IS USUALLY ACCOMPLISHED THROUGH TWO ASSAY METHODS: a) Clot lysis, b) Chromogenic substrate assay. In this study the biological activity of two streptokinase products, namely Streptase®, which is a native product and Heberkinasa®, which is a recombinant product, was determined against the third international reference standard using the two forementioned assay methods. The results indicated that whilst the activity of Streptase® was found to be 101 ± 4% and 97 ± 5% of the label claim with Clot lysis and Chromogenic substrate assay respectively, for Heberkinasa® the potency values obtained were 42 ± 5% and 92.5 ± 2% of the label claim respectively. To shed some light on the reason for this finding, the n-terminal sequence of the streptokinase molecules present in the two products was determined. The results showed slight differences in the amino acid sequence of the recombinant product in comparison to the native one at the amino terminus. This finding supports those of other workers who found that n-terminal sequence of the streptokinase molecule can have significant effect on the activity of this protein.

Comparison of the adjuvanticity of aluminum salts and their combination in hepatitis B recombinant protein vaccine in assessed mice.

BACKGROUND: Several adjuvants have been evaluated for vaccine formulations but aluminum salts will continue to be used for many years due to their safety, low cost and adjuvanticity with different antigens. Two commonly used aluminum adjuvants, aluminum hydroxide and aluminum phosphate have different adjuvanticity properties. Commercial recombinant protein hepatitis B vaccines containing aluminum hydroxide is facing low induction of immunity in some sections of the vaccinated population. OBJECTIVE: In this study, to follow the current global efforts in finding more potent hepatitis B vaccine formulations, adjuvanticity of aluminum phosphate, aluminum hydroxide and their combinations has been evaluated. METHODS: The formulated vaccines were administered intra-peritoneally (i.p.) to BALB/c mice and the titer of antibody was determined after 28 days using ELISA technique. The geometric mean of antibody titer (GMT, mIU/ml), seroconversion and seroprotection rates, ED50 (ng) and relative potency (microg/dose) of different formulations were determined. RESULTS: GMT of antibody titer, seroconversion and seroprotection rates showed significantly higher adjuvanticity for aluminum phosphate than other formulations. The ED50 of aluminum phosphate was approximately two fold less than other formulations. CONCLUSION: Aluminum phosphate showed more adjuvanticity than aluminum hydroxide and their combinations in hepatitis B protein vaccine. The use of aluminum phosphate as adjuvant leads to higher immunity which may result in more protective response in vaccinated groups.