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Production of savinase and population viability of Bacillus clausii during high‐cell‐density fed‐batch cultivations
Author(s) -
Christiansen Torben,
Michaelsen Søren,
Wümpelmann Mogens,
Nielsen Jens
Publication year - 2003
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.10675
Subject(s) - biology , population , flow cytometry , propidium iodide , membrane permeability , membrane , chromatography , chemistry , biochemistry , microbiology and biotechnology , apoptosis , demography , programmed cell death , sociology
The growth and product formation of a Savinase‐producing Bacillus clausii were investigated in high‐cell‐density fed‐batch cultivations with both linear and exponential feed profiles. The highest specific productivity of Savinase was observed shortly after the end of the initial batch phase for all feed profiles applied and, in addition, there was a time‐dependent decrease in specific productivity. The specific glucose uptake rate increased with time for constant specific growth rate indicating that the maintenance requirements increased with time, possibly due to a decreasing K + concentration. The physiological state of the cells was monitored during the cultivations using a flow cytometry assay based on the permeability of the cell membrane to propidium iodide. In the latter parts of the fed‐batch cultures with a linear feed profile, a large portion of the cell population was found to have a permeable membrane, indicating a large percentage of dead cells. By assuming that only cells with a nonpermeable membrane contributed to growth and product formation, the physiological properties of this subpopulation were calculated. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 344–352, 2003.