Dielectric analysis for estimation of oil content in the mycelia of Mortierella alpina

✍ Scribed by Kenichi Higashiyama; Takeshi Sugimoto; Takeshi Yonezawa; Shigeaki Fujikawa; Koji Asami

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 154 KB
• Volume: 65
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/(sici)1097-0290(19991205)65:5<537::aid-bit6>3.0.co;2-o

✦ Synopsis

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 (⌬) 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 ( a ) was also measured. The value of ⌬ 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 ( i ) was calculated from the experimental values of f c and a , using a theoretical equation based on an ellipsoidal cell model. As a result, good correlation between the calculated 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.