ISSN:
0006-3592
Keywords:
specific growth rate
;
hyphal morphometry
;
Aspergillus niger
;
surface growth kinetics
;
glucose effect
;
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Development of surface grown cultures of Aspergillus niger no. 10 was studied at two experimental levels: (a) following the time course of the biomass density (X [=] mg cm-2) and fitting the data by the logistic expression, which yielded a macroscopic specific growth rate expressed as μobs = (dX/Xdt)[1-(X/Xmax)]-1; and (b) measuring morphometric parameters like the specific elongation rate (k) of the germ tubes and their diameters (Dh), the colony rate of radial extension (ur), and the mean length of distal hyphae (Lav) to estimate the specific growth rate with the following proposed expression: μcalc = urln2[Lavln(Lav/Dh)]-1. Increases in the initial glucose concentration (10, 40, 70, 120, 200, and 300 g L-1) caused reductions in the specific growth rates, the elongation kinetics of the germ tubes, and the hyphal diameter, nevertheless, ur and Xmax presented parabolic behavior, showing their maxima in the interval of 90 to 120 g L-1 of glucose. The overall macroscopic effect of the tested concentrations of glucose on surface grown cultures of A. niger was to produce densely packed and slowly extending colonies, where changes in hyphal lengths and diameters were significant. There was good agreement between μobs and μcalc values. Hence, this work validates a kinetic model based on morphometric data to estimate the specific growth rate of molds, obtained from dry weight data, using mold cultures grown in the same solid medium i.e., agar plates. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 287-294, 1997.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
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