The influence of cell concentration and morphology on yielding properties of filamentous fermentatio...

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" The influence of cell concentration and morphology on yielding properties of filamentous fermentation broths "
M. Mohseni Tonkaboni D. G. Allen

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1113280
Doc. No	:	TLpq304160542
Main Entry	:	D. G. Allen
	:	M. Mohseni Tonkaboni
Title & Author	:	The influence of cell concentration and morphology on yielding properties of filamentous fermentation broths\ M. Mohseni TonkaboniD. G. Allen
College	:	University of Toronto (Canada)
Date	:	1994
student score	:	1994
Degree	:	M.A.Sc.
Page No	:	161
Abstract	:	The influence of cell concentration and morphology on the yielding properties of filamentous broths of Aspergillus niger and Streptomyces levoris was investigated using the rotating vane technique and dynamic measurements with a cone and plate viscometer. Cell concentrations ranging from 3 to 20 gdw/L, with corresponding volume fractions between 0.005 and 0.05, were obtained with broths generated in stirred tank and shake flask fermentations. The yield stress values obtained using the vane technique (usd0.1\le\tau\sb{y}\le37usd Pa) correlated with biomass concentration (X, gdw/L) using the equation usd\tau\sb{y} = a{\bf X\sp{b}}usd, where usd2\le{\bf b}\le3.2usd. Increasing the length of organisms significantly increased the yield stress at a given cell concentration; this morphology effect was described using a "morphology factor" (range 0.016 to 0.11 Pa/ (gdw/L) ), determined by setting the value of "b" to 2.5. The vane yield strain was independent of cell concentration but increased with increasing length of organisms. Therefore, both the vane measured yield stress and strain can be used for quantifying the morphology of filamentous organisms. The storage modulus of filamentous fermentation broths was as important as the loss (viscous) modulus at very small deformations, but the storage modulus decreased more rapidly than the loss modulus as the strain increased. A comparison of the dynamic and rotating vane tests shows that the vane technique measures a combination of the viscous and elastic properties and provides a realistic representation of the yield stress at zero shear rate that is significantly higher than the yield stress obtained by extrapolating shear stress-shear rate data to zero shear rate.
Subject	:	Applied sciences
	:	Biological sciences
	:	Chemical engineering
	:	Chemical engineering
	:	Microbiology