Title page for ETD etd-05122000-00440044


Type of Document Master's Thesis
Author Parakulsuksatid, Pramuk
Author's Email Address pramukp@vt.edu
URN etd-05122000-00440044
Title Utilization of a Microbubble Dispersion to Increase Oxygen Transfer in Pilot-Scale Baker’ s Yeast Fermentation Unit
Degree Master of Science
Department Biological Systems Engineering
Advisory Committee
Advisor Name Title
Agblevor, Foster Aryi Committee Chair
Cundiff, John S. Committee Member
Velander, William H. Committee Member
Yousten, Allan A. Committee Member
Keywords
  • baker’ s yeast fermentation
  • pilot-scale
  • oxygen transfer
  • microbubble dispersion
Date of Defense 2000-04-18
Availability unrestricted
Abstract
In the large-scale production of Saccharomyces cerevisiae (baker’ s yeast), oxygen transfer, which is one of the major limiting factors, is improved by using high agitation rates. However, high agitation rates subject the microorganisms to high shear stress and caused high power consumption. A microbubble dispersion (MBD) method was investigated to improve oxygen transfer at low agitation rates and thus reduce power consumption and shear stress on the microorganisms. The experiments were conducted at the 1-liter level and subsequently scaled-up to 50-liters using a constant volumetric oxygen transfer coefficient (kLa) method for scaling. In comparison to a conventional air-sparged fermentation, the MBD method considerably improved the cell mass yield, growth rate and power consumption in the50-liter fermentor. Cell mass production in the MBD system at agitation rate of 150 rpm was about the same as those obtained for a conventional air-sparged system agitatid at 500 rpm. Power consumption in the conventional air-sparged system was three-fold that required for the same biomass yield in the MBD system. However, at the 1-liter scale, the MBD system did not show any significant advantage over the air-sparged system because of the high power consumption.
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