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Dielectric analysis for estimation of oil content in the mycelia of Mortierella alpina
Author(s) -
Higashiyama Kenichi,
Sugimoto Takeshi,
Yonezawa Takeshi,
Fujikawa Shigeaki,
Asami Koji
Publication year - 1999
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/(sici)1097-0290(19991205)65:5<537::aid-bit6>3.0.co;2-o
Subject(s) - dielectric , conductivity , mycelium , permittivity , relaxation (psychology) , volume fraction , materials science , chemistry , analytical chemistry (journal) , botany , chromatography , biology , composite material , optoelectronics , neuroscience
The dielectric behavior of the filamentous fungi Mortierella alpina SAM2104 and 1S‐4, which produce polyunsaturated fatty acid enriched oil in the mycelia, was investigated. During the cultivation carried out in a 10‐kL fermentor for 12–15 days, the relative permittivity and conductivity of the broth were measured in the frequency range of 100 kHz to 30 MHz. The dielectric parameters, i.e., the amplitude of dielectric relaxation (Δϵ) and the characteristic frequency ( f c ), were obtained by fitting the Cole–Cole equation to the observed dielectric relaxation, and the conductivity of the medium (κ a ) was also measured. The value of Δϵ gradually increased from the second day through the end of cultivation, suggesting that volume fraction of the cell increased with oil accumulation. The conductivity of the cytoplasm (κ i ) was calculated from the experimental values of f c and κ a , using a theoretical equation based on an ellipsoidal cell model. As a result, good correlation between the calculated κ i and the oil content was obtained. These findings indicate that dielectric analysis enables us to estimate the oil content in the mycelia of oleaginous fungi and also provides a useful tool for monitoring cell growth and for controlling the cultivation process. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 65:537–541, 1999.