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Direct measurement of the yield stress of filamentous fermentation broths with the rotating vane technique
Author(s) -
LeongPoi Lisa,
Allen D. Grant
Publication year - 1992
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260400310
Subject(s) - fermentation , viscometer , yield (engineering) , shear stress , materials science , bioreactor , chromatography , cylinder , concentric , stress (linguistics) , chemistry , viscosity , mathematics , composite material , food science , geometry , organic chemistry , linguistics , philosophy
The existence of a yield stress in filamentous fermentation broths has important transport phenomena implications in the design and operation of bioreactors. In this study, the constant shear rate vane method was assessed for directly measuring the yield stress of filamentous Aspergillus niger fermentation broths, as well as model fluids (ketchup, yogurt, and pulp suspensions). The method involved rotating 4‐, 6‐, and 8‐bladed vanes (7.2 cm ≤ height ≤ 15 cm; 4.0 cm ≤ dia. ≤ 6 cm) at speeds of 0.01 to 0.64 rpm in the fluid and plotting the torque as a function of time. Based on visual observations, the consistency of the results with vane type and speed and comparison with previous work on nonbiological samples, it was concluded that the method is an effective and consistent technique for yield stress measurements on filamentous fermentation broths. Based on comparisons with concentric cylinder viscometer results, it was also concluded that the value determined via the vane method was a “static” yield stress (values of up to 28 Pa) which was much greater than the extrapolated (or “dynamic”) yield stress determined via the concentric cylinder viscometer. © 1992 John Wiley & Sons, Inc.