Browsing by Author "Gelmi, C"

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    Modelling Gibberella fujikuroi growth and GA(3) production in solid-state fermentation
    (ELSEVIER SCI LTD, 2002) Gelmi, C; Perez Correa, R; Agosin, E
    A simple differential equation model was developed to represent the growth and production of a secondary metabolite in solid-state cultivation (SSC) under conditions of limited nitrogen. The model was used to interpret data obtained from SSCs of the fungus Gibberella fujikuroi, under different temperatures (25 and 31 degreesC) and water activity conditions (0.985, 0.992, 0.999). The model was calibrated in two steps. An innovative procedure to achieve good initial guesses for key parameters, such as maintenance coefficients and death rates was first applied. These initial guesses were then used in a non-linear optimisation routine to get a minimum least squares fit for the model. The mathematical model was able to reproduce the measured variables: biomass, urea, starch, CO2, O-2 and GA(3) satisfactorily. Moreover. the model indicated that the fungus does not assimilate the nitrogen source, urea, directly. The model will be useful in developing optimal feeding policies and on-line biomass estimators. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.
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    Solid substrate cultivation of Gibberella fujikuroi on an inert support
    (ELSEVIER SCI LTD, 2000) Gelmi, C; Perez Correa, R; Gonzalez, M; Agosin, E
    Growth of Gibberella fujikuroi on Amberlite, an inert support, and gibberellic acid (GA,) production was studied in glass columns under different conditions of temperature and water activity (a(w)). Maximum biomass concentration and GA(3) production were respectively 40 (mg/g inert support) and 0.73 (mg/g inert support). While high specific growth rates were obtained, low initial nitrogen resulted in low biomass concentrations. Maximum GA(3) (31 degrees C, a(w)=0.985) was not produced by the maximum concentration of biomass (25 degrees C, a(w)=0.992). Peaks in the rate curves of either outlet gas, CO2 or O-2 occurred on exhaustion of urea indicating, for future works, just when to feed the culture additional nitrogen. (C) 2000 Elsevier Science Ltd. All rights reserved.