Design and physical characteristics of a multistage,continuous tower fermentor

A multistage tower laboratory fermentor has been constructed consisting of eight compartments separated by sieve plates. Flow of substrate and air is concurrent from the bottom to the top of the column. It, was hoped that this system could be used to reproduce, simultaneously on a continuous basis, eight distinct phases of a batch growth curve. It was believed that the extent of batch curve simulation would depend upon the character of hydraulic mean residence time of broth in the column and in the individual compartments. The expected relationship did not occur. Rather it was found that growth in the column involved residence time characteristics not only for the fluid but also for the microorganisms, and for the growth limiting substrate. Depending upon the column operation, these could be distinct and different. The purpose of this investigation was to study the residence time distribution (RTD) of the continous (fluid) and dispersed (microorganisms) phases for model systems as well as for a yeast fermentation. Various degrees of flow nonideality, i.e., fluid blackflow and dispersed phase sedimentation, were noticed. The former seems to be due to interaction of the concurrent gas and liquid flow; it is particularly dependent upon void area of the sieve plate holes. Sedimentation is probably a function of plate design as well as cell size and density. It wa concluded that for a particular plate design the gas hold-up wass controlled by superficial air velocity and was the main parameter governing the differences between dispersed and continous phase(Rt1). This conclusion was supported by a computeraided styudy utilizing a mathematical model of fluid flow to fit the growth kinetics and cell distribution observed experimentally throughout the fermentor. Some advantages of foam control in the tower fermentor by surface active compounds are mentioned. Also, suggestions are made for carrying out fermentations that have two liquid phases, such as a hydrocarbon fermentation. The possibility of closely approximating plug-flow conditions in the multistage tower fermentor, a necessary condition for batch growth simulation, is discussed from a practical point of view.     

Relationship between adenohypophyseal and steroid hormones and variations in serum and urinary melatonin levels during the ovarian cycle, perimenopause and menopause in healthy women

Morning levels of serum melatonin, FSH, LH, prolactin (PRL), progesterone and estradiol were studied by RIA during the ovarian cycle, perimenopause and menopause in 79 healthy women. FSH and LH levels showed a slight nonsignificant increase from the fertile period to perimenopause, exhibiting a significantly greater increase during menopause. PRL, progesterone and estradiol showed parallel changes, reaching lower levels during menopause. Serum melatonin levels decreased with age, attaining minimum levels in menopause. FSH and estradiol were significantly correlated with melatonin in the follicular phase, while in the luteal phase a negative correlation was found between melatonin, progesterone and estradiol. No significant correlations were noted between serum hormone levels during the perimenopausal period. In menopause, as during the follicular phase, melatonin and FSH were negatively correlated. As expected, a significant positive correlation was found between morning serum levels of melatonin and nocturnal urinary excretion of this indoleamine in all groups studied.     

Genetic studies on the acidification capacity of sunflower roots induced under iron stress

Under stress of iron deficiency roots of sunflower (Helianthus annuus L.) increase proton efflux which acidifies the root medium, increase the ferric reducing capacity and the exudation of phenolic compounds. Differences have been found previously among sunflower inbred lines in the capacity of their roots to lower pH and it was also found that this character is under genetic control.This work presents the results of an inheritance study made by crossing two genotypes, one (CMS HA 89) without acidification capacity and another (RHA 271) with it. Plants were grown individually in 75 mL vessels with an aerated solution low in iron. After 4 days, solutions were changed to one without iron and the pH of the medium was measured during the following days. Results from F₁, F₂, and backcross generations can be explained with two pairs of alleles controlling the character, being the relation between alleles of complete dominance at both gene pairs, but either gene, when dominant is epistatic to the other.     

Internal protein sequence analysis: enzymatic digestion for less than 10 micrograms of protein bound to polyvinylidene difluoride or nitrocellulose membranes.

A procedure for the generation and isolation of internal peptide fragments for less than 10 micrograms of protein bound to either polyvinylidene difluoride (PVDF) or nitrocellulose membranes after electrophoretic transfer from sodium dodecyl sulfate-polyacrylamide gels (SDS-PAGE) is presented. This technique has produced internal sequence data for 120 peptides, with an average initial yield of 20 pmol. Membrane-bound proteins were enzymatically digested with either trypsin or endoproteinase Lys-C in the presence of 1% hydrogenated Triton X-100/10% acetonitrile/100 mM Tris-HCl, pH 8.0, for 24 h at 37 degrees C. The eluted peptides were then directly isolated by microbore HPLC for subsequent sequence analysis. One percent hydrogenated Triton X-100 did not inhibit enzymatic activity, distort HPLC resolution of peptides, or contain uv-absorbing contaminants that could interfere with peptide identification. Reproducible peptide maps and consistent recoveries are presented for standard proteins (3.5-8.0 micrograms) bound to either membrane, with higher recoveries for PVDF-bound proteins. Ninety percent of the proteins analyzed by this technique have produced results; representative peptide maps and sequence data are presented. This technique has a wide range of applications, particularly for proteins with blocked amino termini or those that can only be purified by SDS-PAGE or 2D isoelectric focusing SDS-PAGE.     

Acyl carrier protein (ACP) import into chloroplasts does not require the phosphopantetheine: evidence for a chloroplast holo-ACP synthase.

Import of the acyl carrier protein (ACP) precursor into the chloroplast resulted in two products of about 14 kilodalton (kD) and 18 kD when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Time course experiments indicate that the latter is a modification derivative of the 14-kD peptide after the removal of the transit peptide. Substitution of serine 38 by alanine, eliminating the phosphopantetheine prosthetic group attachment site of ACP, produced a precursor mutant that gave rise to only the 14-kD peptide during import, showing that the modified form depends on the presence of serine 38. Furthermore, these results demonstrate that the prosthetic group is not essential for ACP translocation across the envelope or proteolytic processing. Analysis of the products of import by nondenaturing, conformationally sensitive gels showed reversal of the relative mobility of the 14-kD peptide and the modified form, raising the possibility that the modification is the addition of the phosphopantetheine. Proteolytic processing and the modification reaction were reconstituted in an organelle-free assay. The addition of coenzyme A to the organelle-free assay completely converted the 14-kD peptide to the modified form at 10 micromolar, and this only occurred with the wild-type substrate. Reciprocally, treatment of the products of a modification reaction with Escherichia coli phosphodiesterase converted the modified ACP from back to the 14-kD peptide. These results strongly support the conclusion that there is a holo-ACP synthase in the soluble compartment of the chloroplast capable of transferring the phosphopantetheine of coenzyme A to ACP.     

Ultrastructural analysis of mineralized matrix from human osteoblastic cells: Effect of tumor necrosis factor-alpha

The study, addressed to understand whether or not human platelets possess a unique thiol-oxidase whose activity could be modulated by signalling pathway initiated upon the activation of Receptor-C_k revealed the existence of disulphide-dependent oxidation within these cells and this phenomenon was regulated by Receptor-C_k-dependent generation of second messengers especially phosphatidic acid (PA); cAMP and cGMP. Purification of this activity revealed the existence of 47 kDa protein having thiol-oxidase activity. Keeping in view these results we propose that the existence of this novel 47 kDa Thiol-oxidase within human platelets may provide a crucial switch for the regulation of Receptor-C_k-dependent mevalonate pathway in human platelets.