Search results for "Bioengineering"
showing 10 items of 1963 documents
Ultrasound-assisted green solvent extraction of high-added value compounds from microalgae Nannochloropsis spp.
2015
Abstract The aim of this work was to investigate ultrasound (US)-assisted green solvent extraction of valuable compounds from the microalgae Nannochloropsis spp. Individual green solvents (water, ethanol (EtOH), dimethyl sulfoxide (DMSO)) and binary mixture of solvents (water-DMSO and water-EtOH) were used for the extraction procedures. Maximum total phenolic compounds yield ( Y p ≈ 0.33) was obtained after US pre-treatment ( W = 400 W, 15 min), being almost 5-folds higher compared to that found for the untreated samples and aqueous extraction ( Y p ≈ 0.06). The highest yield of total chlorophylls ( Y c ≈ 0.043) was obtained after US ( W = 400 W, 7.5 min), being more than 9-folds highe…
Cr(VI) sorption by intact and dehydrated Candida utilis cells in the presence of other metals
2002
This study examined the Cr(VI), Cu(II), Zn(II), Cd(II), Pb(II) sorption by intact and dehydrated Candida utilis cells. The anion [Cr2O7]2− and cation Me2+ sorption kinetics was investigated in both single- and dual-metal situations. Uptake of chromate anions occurred much more slowly singularly than with metal cations. A combination of Pb or Cu and chromate anions gave a synergistic effect for Cr(VI) sorption, but not Cd and Zn, which inhibited Cr(VI) sorption by dehydrated cells. The use of alcian blue to occupy maximum vacant adsorption sites on the cell surface unexpectedly did not influence further adsorption of Me2+. Metal uptake by C. utilis was 7 mg (135 μM) Cr, 23 mg (362 μM) Cu, 39…
Pullulan and dextran: uncommon composition dependent Flory-Huggins interaction parameters of their aqueous solutions.
2008
Vapor pressure measurements were performed for aqueous solutions of pullulan ( M w 280 kg/mol) and dextran ( M w 60 and 2100 kg/mol, respectively) at 25, 37.5, and 50 degrees C. The Flory-Huggins interaction parameters obtained from these measurements, plus information on dilute solutions taken from the literature, show that water is a better solvent for pullulan than for dextran. Furthermore, they evince uncommon composition dependencies, including the concurrent appearance of two extrema, a minimum at moderate polymer concentration and a maximum at high polymer concentration. To model these findings, a previously established approach, subdividing the mixing process into two clearly separa…
Simulation Analysis of the Influence of Hemodialysis Control Parameters on Exchange Processes during Therapy
1992
The effect of dialysis control parameters (dialysate composition, ultrafiltration rate, blood flow rate) on the patient's internal milieu were studied using a mathematical model for the description of the dynamic exchange processes during hemodialysis. This model simulates the electrolyte and water distribution, the acid-base and the oxygenation state as well as the ventilation. The dialysate sodium concentration affects mainly the intra-/ extracellular water and the potassium distribution. The dialysate bicarbonate and acetate concentrations control the acid-base state and the electrolyte distribution (sodium and potassium). In addition, the dialysate acetate concentration has a strong ef…
Evaluation of dynamic microbial communities in a styrene-degrading biotrickling filter using 16S rDNA tag pyrosequencing and denaturing gradient gel …
2014
Accurately characterizing microbial communities within bioreactors undergoing dynamic operating conditions is an essential first step towards understanding the relationship between microbial community structure and bioreactor performance. A detailed assessment of the changes in microbial populations within a styrene-degrading biotrickling filter was carried out using samples collected at multiple time points ranging from 21 to 155 days of biotrickling filter operation. Examination of microbial populations was conducted by 16S rDNA tag pyrosequencing and denaturing gradient gel electrophoresis (DGGE). Validation of pyrosequencing results was performed by quantitative polymerase chain reactio…
Modeling of continuous Ph-stat stirred tank reactor withLactococcus lactisssp.lactisbv.diacetylactisimmobilized in calcium alginate gel beads
1995
A dynamic diffusion-reaction-growth model is proposed for the study of lactic fermentation, the bioconversion of citric acid, and cell release in an immobilized cell reactor [pH-stat continuous stirred tank-reactor (CSTR)]. The model correctly simulates the onset of fermentation and colonization of the gel, followed by the steady state. External diffusion is nonlimiting and internal diffusion is limited by high cell densities at the periphery of the gel beads. Lactose-citrate cometabolism in the gel is related to the distribution of active included biomass within the gel and to gradients of substrates (lactose, citrate) and products (lactate, pH) in the beads. The utilization of lactose is …
Levan-ethanol biosynthesis using Zymomonas mobilis cells immobilized by attachment and entrapment
2001
Fermentation of sucrose by Zymomonas mobilis cells attached to stainless steel wire spheres (WS) and to Al2O3 granules was compared with sucrose fermentation by cells entrapped in Ca-alginate. Similar amounts of cell biomass were applied at the beginning of the immobilized fermentation systems. The immobilization of Z. mobilis cells to the carrier surface was checked by scanning electron microscopy (SEM). Most cells were present in holes and pores of Al2O3 surfaces following colonization. Observation of the carrier after repeated fermentation cycles showed that a surface of Al2O3 granules was partly covered by levan. Alginate beads were extended in volume and partly disrupted. Changing the …
Purification and Characterization of <I>Bacillus cereus</I> Protease Suitable for Detergent Industry
2005
An extracellular alkaline protease from an alkalophilic bacterium, Bacillus cereus, was produced in a large amount by the method of extractive fermentation. The protease is thermostable, pH tolerant, and compatible with commercial laundry detergents. The protease purified and characterized in this study was found to be superior to endogenous protease already present in commercial laundry detergents. The enzyme was purified to homogeneity by ammonium sulfate precipitation, concentration by ultrafiltration, anion-exchange chromatography, and gel filtration. The purified enzyme had a specific activity of 3256.05 U/mg and was found to be a monomeric protein with a molecular mass of 28 and 31 kD…
Comparative studies on cytotoxic effects of dental amalgams and alternative alloys according to ISO standards in vitro
1995
Deleterious effects of dental alloys, especially those of dental amalgams, have become an important issue in current discussions on biomaterials. Cytotoxicity and further related risks of amalgams are discussed in a controversial way in the literature without leading to a final conclusion. There is still a need for basic clinical and pre-clinical research, especially with respect to the wide distribution of dental amalgams. Standardized methods of cytotoxicity testing have been established by the ISO. It was the aim of the present study to detect and compare possible cytotoxic effects of dental amalgams and alternative non-amalgam alloys in vitro. According to the ISO standards, direct cont…
Aerobic granular sludge treating shipboard slop: Analysis of total petroleum hydrocarbons loading rates on performances and stability
2018
Abstract The work focuses on the feasibility of treating slop with aerobic granular sludge. For this purpose, a 3.5 L granular sequencing batch reactor was activated and it was monitored for 156 days. The experimental campaign was divided into two periods, named Period I (100 days) and Period II (56 days). Total Petroleum Hydrocarbon (TPH) concentration in the slop was, on average, equal to 6.8 ± 1.5 mg L−1 and 13 ± 1.5 mg L−1 in Period I and Period II respectively. The obtained results during the first experimental period indicated that about 80 days were required to reach steady state with mature granules, when TPHs removal efficiency was approximately 90%. The results indicated that both…