Extraction of Fungal Fatty Acids for Gas Chromatography Analysis

Abstract

The standard method for the extraction of fatty acids from fungi recommended in association with commercially produced fatty acid analysis sys- tems (MIDI Inc., Newark, Delaware) was compared with methods utilizing a Polytron homogenizer and vortexing with glass beads for disruption of fungal mycelia. The extraction efficiencies and variability were compared utilizing two isolates of Ceratocystis fagacearum, the causal agent of oak wilt. Using a Poly- tron homogenizer significantly reduced the fatty acid levels (61%) when compared to the standard meth- od. Vortexing with glass beads (425-600 rtm) in- creased the fatty acid levels (49%) and reduced var- iability (20%) when compared to the standard meth- od. Different sizes of glass beads (150-212 jLm, 425- 600 pLm, 710-1180 jum) did not yield significant dif- ferences in extraction efficiency with the fatty acid levels with 150-212 jim and 710-1180 JUm being 71% and 59% compared to the use of 425-600 Im glass beads. The addition of 1 g glass beads/sample fol- lowed by vortexing for 2 min is easily adapted in any laboratory conducting fatty acid analysis without ad- ditional equipment. The reduction in the variability of samples would be extremely important when look- ing for minor changes in fatty acid percentages and composition. The standard recommended growth temperature (28 C) was decreased (22 C) for maxi- mal growth of C. fagacearum. No significant differ- ences were noted between the use of SDB and PDB except in the level of 14:0 fatty acid which was a mi- nor component in the total levels of fatty acids (0.7