Mean drop behavior in the standard liquid-liquid extraction systems on an L-shaped pulsed sieve-plate column: experiment and modeling.

In this study, the effect of operating parameters on drop behavior was investigated experimentally in an L-shaped pulsed sieve-plate column (LPSPC). LPSPC offers enhanced efficiency due to a high mixing rate provided by pneumatic or hydraulic pulsation of the liquids, which makes the dispersed phase drops coalesce and break. The response surface methodology (RSM) based on the central composite design (CCD) approach was applied for experimental modeling of three standard systems including toluene-water, butyl acetate-water, and butanol-water. Four parameters including pulsation intensity, interfacial tension, dispersion, and continuous phase velocities were examined in the experiments. Experimental results indicated that an increase in the pulsation intensity led to a decrease in Sauter mean diameter (SMD), and an increase in the flow rates of the phase cause an increase in SMD, although the effect of the flow rates on SMD was much lower than the pulsation intensity. Based on the obtained experimental data, new correlations have been proposed to predict SMD in two sections of the column tested by the goodness-of-fit statistics through analysis of variance. The coefficient of determination was achieved at 0.998 and 0.978 for horizontal and vertical sections, respectively, which demonstrated that the presented models estimated the experimental values very well. The optimum SMDs were obtained at 0.789 mm and 0.639 mm for the horizontal and vertical sections, respectively.

Structural and molecular properties of complexes of biomolecules and metal-organic frameworks: dispersion-corrected DFT treatment.

Investigation of complexes of nanostructured materials and biomolecules has attracted much attention by various researchers as it can contribute to coherent growth and extended application of nanostructures in different technologies. In this research, following a comprehensive approach, we examined the interaction between different amino acids and metal-organic frameworks (MOFs) at atomic scale using computational chemistry. For this purpose, we employed the density functional theory (DFT-D2) calculations to afford a molecular description of the interaction properties of the amino acids and MOF-5 by examining the interaction energy and the electronic structure of the amino acid/MOF complexes. We found strong interactions between the amino acids and MOF through their polar groups as well as aromatic rings in the gas phase. However, our findings were significantly different in solvent media, where water molecules prevent the amino acids from approaching the active sites of MOF, causing weak attractions between them. The evaluation of nature of interaction between the amino acids and MOF by the atoms-in-molecules (AIM) theory shows that the electrostatic attractions are the main force contributing to bond formation between the interacting entities. Furthermore, our DFT-PBE model of theory was validated against the comprehensive MP2 quantum level of theory.

Growth kinetic models of five species of Lactobacilli and lactose consumption in batch submerged culture

Abstract Kinetic behaviors of five Lactobacillus strains were investigated with Contois and Exponential models. Awareness of kinetic behavior of microorganisms is essential for their industrial process design and scale up. The consistency of experimental data was evaluated using Excel software. L. bulgaricus was introduced as the most efficient strain with the highest biomass and lactic acid yield of 0.119 and 0.602 g g-1 consumed lactose, respectively. The biomass and carbohydrate yield of L. fermentum and L. lactis were slightly less and close to L. bulgaricus. Biomass and lactic acid production yield of 0.117 and 0.358 for L. fermentum and 0.114 and 0.437 g g-1 for L.actobacillus lactis were obtained. L. casei and L. delbrueckii had the less biomass yield, nearly 11.8 and 22.7% less than L. bulgaricus, respectively. L. bulgaricus (R 2 = 0.9500 and 0.9156) and L. casei (R 2 = 0.9552 and 0.8401) showed acceptable consistency with both models. The investigation revealed that the above mentioned models are not suitable to describe the kinetic behavior of L. fermentum (R 2 = 0.9367 and 0.6991), L. delbrueckii (R 2 = 0.9493 and 0.7724) and L. lactis (R 2 = 0.8730 and 0.6451). Contois rate equation is a suitable model to describe the kinetic of Lactobacilli. Specific cell growth rate for L. bulgaricus, L. casei, L. fermentum, L. delbrueckii and L. lactis with Contois model in order 3.2, 3.9, 67.6, 10.4 and 9.8-fold of Exponential model.

Growth kinetic models of five species of Lactobacilli and lactose consumption in batch submerged culture.

Kinetic behaviors of five Lactobacillus strains were investigated with Contois and Exponential models. Awareness of kinetic behavior of microorganisms is essential for their industrial process design and scale up. The consistency of experimental data was evaluated using Excel software. L. bulgaricus was introduced as the most efficient strain with the highest biomass and lactic acid yield of 0.119 and 0.602gg-1 consumed lactose, respectively. The biomass and carbohydrate yield of L. fermentum and L. lactis were slightly less and close to L. bulgaricus. Biomass and lactic acid production yield of 0.117 and 0.358 for L. fermentum and 0.114 and 0.437gg-1 for L.actobacillus lactis were obtained. L. casei and L. delbrueckii had the less biomass yield, nearly 11.8 and 22.7% less than L. bulgaricus, respectively. L. bulgaricus (R2=0.9500 and 0.9156) and L. casei (R2=0.9552 and 0.8401) showed acceptable consistency with both models. The investigation revealed that the above mentioned models are not suitable to describe the kinetic behavior of L. fermentum (R2=0.9367 and 0.6991), L. delbrueckii (R2=0.9493 and 0.7724) and L. lactis (R2=0.8730 and 0.6451). Contois rate equation is a suitable model to describe the kinetic of Lactobacilli. Specific cell growth rate for L. bulgaricus, L. casei, L. fermentum, L. delbrueckii and L. lactis with Contois model in order 3.2, 3.9, 67.6, 10.4 and 9.8-fold of Exponential model.

Single Cell Protein Production by Saccharomyces cerevisiae Using an Optimized Culture Medium Composition in a Batch Submerged Bioprocess.

Saccharomyces cerevisiae PTCC5269 growth was evaluated to specify an optimum culture medium to reach the highest protein production. Experiment design was conducted using a fraction of the full factorial methodology, and signal to noise ratio was used for results analysis. Maximum cell of 8.84 log (CFU/mL) was resulted using optimized culture composed of 0.3, 0.15, 1, and 50 g L(-1) of ammonium sulfate, iron sulfate, glycine, and glucose, respectively at 300 rpm and 35 °C. Glycine concentration (39.32 % contribution) and glucose concentration (36.15 % contribution) were determined as the most effective factors on the biomass production, while Saccharomyces cerevisiae growth had showed the least dependence on ammonium sulfate (5.2 % contribution) and iron sulfate (19.28 % contribution). The most interaction was diagnosed between ammonium sulfate and iron sulfate concentrations with interaction severity index of 50.71 %, while the less one recorded for glycine and glucose concentration was equal to 8.12 %. An acceptable consistency of 84.26 % was obtained between optimum theoretical cell numbers determined by software of 8.91 log (CFU/mL), and experimentally measured one at optimal condition confirms the suitability of the applied method. High protein content of 44.6 % using optimum culture suggests that Saccharomyces cerevisiae is a good commercial case for single cell protein production.

Effects of Phenylglyoxal and N-ethylmaleimide Concentration on Mycophenolic Acid Production by Penicillium brevi-compactum ATCC16024.

Mycophenolic acid is a secondary extracellular metabolite of Penicillium strains with numerous pharmaceutical properties such as antibiotic and immunosuppressive uses. The aim of this work is the survey of the effect of phenylglyoxal and n-ethylmaleimide concentration in culture medium on mycophenolic acid production by Penicillium brevi-compactum ATCC16024 was investigated. Batch submerged fermentation was performed in 250 mL shake flasks at 24 °C and 200 rpm in a rotary shaker for 300 h using a basic culture medium containing different concentrations of phenylglyoxal and n-ethylmaleimide ranged from 0 to 20 mg. L-1. For the basic medium without any amounts of phenylglyoxal and n-ethylmaleimide (control), maximum MPA production, product yield and productivity of process was in order, 1.5042 g. L-1, 20.3 mg. g-1 consumed glucose and 5.37 mg. L-1h-1. Maximum produced MPA of 2.9032 g. L-1, MPA yield of 39.23 mg. g-1 of consumed glucose, productivity of 10.37 mg. L-1 h-1 and total enhancement of 93.11% was obtained when the culture medium was contained 18 mg. L-1 of phenylglyoxal, represented more than 93% raising in compare to control. Maximum MPA concentration, yield and productivity in order was obtained 3.1123 g. L-1, 42.06 mg. g-1 of consumed glucose and 11.11 mg. L-1 h-1, with using 6 mg. L-1 of n-ethylmaleimide. N-ethylmaleimide was caused to 2.138 folds (106.89%) increase in MPA production by P. brevi-compactum ATCC16024.