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 morphologyReportar como inadecuado




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 - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Microbial Cell Factories

, 5:3

First Online: 25 January 2006Received: 15 December 2005Accepted: 25 January 2006

Abstract

BackgroundAlthough 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 10 to 10 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.

ResultsCell volume fraction analysis for the various inoculum levels tested revealed that by rising the spore inoculum level from 10 to 10 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 10 and 10 spores-ml, where pellets predominated. At much higher inoculum levels 10, 10 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 10 to 10 spores-ml, while in aggregated forms particle sizes and their compactness decreased.

ConclusionThe methods used in this study, allowed for the detailed quantification of the transition between the two extreme morphological forms. The impact of spore inoculum level on the detailed characteristics of the particular morphological forms produced was high. Control of mycelial morphology is often regarded as a prerequisite to ensure increased productivities in industrial applications. The research described here demonstrates that adjusting the spore inoculum level controls effectively mycelial morphology.

Electronic supplementary materialThe online version of this article doi:10.1186-1475-2859-5-3 contains supplementary material, which is available to authorized users.

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Autor: Maria Papagianni - Michael Mattey

Fuente: https://link.springer.com/







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