53 research outputs found
Morphological development of Aspergillus niger in submerged citric acid fermentation as a function of the spore inoculum level. Application of neural network and cluster analysis for characterization of mycelial morphology
No full textAlthough the citric acid fermentation by Aspergillus niger is one of the most important industrial microbial processes and various aspects of the fermentation appear in a very large number of publications since the 1950s, the effect of the spore inoculum level on fungal morphology is a rather neglected area. The aim of the presented investigations was to quantify the effects of changing spore inoculum level on the resulting mycelial morphology and to investigate the physiology that underlines the phenomena. Batch fermentations were carried out in a stirred tank bioreactor, which were inoculated directly with spores in concentrations ranging from 104 to 109 spores per ml. Morphological features, evaluated by digital image analysis, were classified using an artificial neural network (ANN), which considered four main object types: globular and elongated pellets, clumps and free mycelial trees. The significance of the particular morphological features and their combination was determined by cluster analysis. Cell volume fraction analysis for the various inoculum levels tested revealed that by rising the spore inoculum level from 104 to 109 spores per ml, a clear transition from pelleted to dispersed forms occurs. Glucosamine formation and release by the mycelium appears to be related to spore inoculum level. Maximum concentrations detected in fermentations inoculated with 104 and 105 spores/ml, where pellets predominated. At much higher inoculum levels (108, 109 spores/ml), lower dissolved oxygen levels during the early fermentation phase were associated with slower ammonium ions uptakes and significantly lower glucosamine concentrations while the mycelium developed in dispersed morphologies. A big increase in the main and total hyphal lengths and branching frequency was observed in mycelial trees as inoculum levels rise from 104 to 109 spores/ml, while in aggregated forms particle sizes and their compactness decrease
Effects of California migration
No full textCalifornia ; Emigration and immigration ; West (U.S.) ; Federal Reserve District, 12th
Changes in primary metabolism leading to citric acid overflow in aspergillus niger
No full textFor citric acid-accumulating Aspergillus niger cells, the enhancement of anaplerotic reactions replenishing tricarboxylic acid cycle intermediates predisposes the cells to form the product. However, there is no increased citrate level in germinating spores and a complex sequence of developmental events is needed to change the metabolism in a way that leads to an increased level of tricarboxylic acid cycle intermediates in mycelia. A review of physiological events that cause such intracellular conditions, with the special emphasis on the discussion of hexose transport into the cells and regulation of primary metabolism, predominantly of glycolytic flux during the process, is presented
A Universal Anaphylaxis Emergency Care Plan: Introducing the New Allergy and Anaphylaxis Care Plan From the American Academy of Pediatrics
No full text Anaphylaxis is a life-threatening emergency. In the school setting, school nurses prepare plans to prevent an emergency, educating staff and students on life-threatening allergies. A critical component of any emergency plan is a plan of care in the event of accidental ingestion or exposure to an antigen to prevent the sequelae of untreated anaphylaxis. A universal anaphylaxis emergency care plan developed by the American Academy of Pediatrics and reviewed by NASN offers an opportunity for schools, family, and health care providers to use one standard plan and avoid confusion. The plan and benefits of use are described in this article. </jats:p
Bacteriophage therapy - cooked goose or Phoenix rising?
No full textRecent animal and human trials of bacteriophage therapy have demonstrated its potential to alleviate bacterial diseases, both in internal and in external applications. The regulatory requirements are becoming clearer as more examples are presented. A core of GLP (Good Laboratory Practice) studies will be needed to validate safety and clinical trials to validate efficacy. GMP (Good Manufacturing Practice) production requirements and quality issues will mean that comparable costs to the production of conventional antibiotics should be anticipated. The definition of the 'active substance' will be central to the success of bacteriophage therapy to ensure that the variety and evolutionary potential of bacteriophages are exploited
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Premature germination of resting spores as a means of Protecting brassica crops from Plasmodiophora brassicae Wor., (clubroot)
No full textPremature germination of resting spores as a means of protecting brassica crops from Plasmodiphora brassicae Wor., (Clubroot). Crop Protection. Clubroot disease causes substantial yield and quality losses in broadacre oil seed and intensive vegetable brassica crops worldwide. The causal microbe Plasmodiophora brassicae Wor., perennates as soil-borne dormant resting spores. Their germination is triggered by exudates from host roots. A valuable addition to sustainable integrated control strategies could be developed by identifying and synthesising the molecules responsible for stimulating resting spore germination. This paper reports experiments in which stimulatory exudates were collected from brassica roots following exposure to infective stages of P. brassicae. Analyses identified a germination signalling molecule of circa 1 kDa formed of glucose sub-units. Mass spectral analyses showed this to be a complex hexasaccharide carbohydrate with structural similarities to the components of plant cell walls. This is the first report of a host generated hexasaccharide which is capable of stimulating the germination of resting spores of P. brassicae. The implications for environmentally benign control of clubroot are discussed briefly
Improving Parametric Mortgage Prepayment Models with Non-parametric Kernel Regression
No full textDeveloping a good prepayment model is a central task in the valuation of mortgages and mortgage-backed securities but conventional parametric models often have bad out-of-sample predictive ability. A likely explanation is the highly non-linear nature of the prepayment function. Non-parametric techniques are much better at detecting non-linearity and multivariate interaction. This article discusses how non-parametric kernel regression may be applied to loan level event histories to produce a better parametric model. By utilizing a parsimonious specification, a model can be produced that practitioners can use in valuation routines based on Monte Carlo interest rate simulation.
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