Quantitative assessment of the degree of lipid unsaturation in intact Mortierella by Raman microspectroscopy
- 394 Downloads
Fungi of the genus Mortierella can accumulate large amounts of unusual lipids depending on species, strain, and growth conditions. Fast and easy determination of key parameters of lipid quality for these samples is required. In this contribution, we apply Raman microspectroscopy to determine the degree of unsaturation for fungal lipids directly inside intact hyphae without elaborate sample handling. Six Mortierella species were grown under varying conditions, and Raman spectra of single lipid vesicles were acquired. From the spectra, we calculate a peak intensity ratio I(1270 cm−1)/I(1445 cm−1) from the signals of =CH and –CH2/–CH3 groups, respectively. This ratio is linked to the iodine value (IV) using spectra of reference compounds with known IV. IVs of fungal samples are compared to gas chromatography results. Values from both methods are in good accordance. Lipid composition is found to vary between the investigated species, with Mortierella alpina having the most unsaturated lipid (IV up to 280) and Mortierella exigua the least unsaturated (IV as low as 70). We find Raman microspectroscopy a suitable tool to determine the IV reliably, fast, and easily inside intact hyphae without extensive sample handling or treatment. The method can also be transferred to other microscopic samples.
KeywordsOleaginous fungi Mortierellales Mortierellomycotina Lipid bodies Polyunsaturated fatty acids Arachidonic acid production
Financial support from the Jena School for Microbial Communication as well as funding of the research group “Jenaer Biochip Initiative 2.0” within the framework “Unternehmen Region—InnoProfile Transfer” from the Federal Ministry of Education and Research, Germany (BMBF, grant number 03IPT513Y) is gratefully acknowledged.
- 11.Chaudhuri S, Ghosh S, Bhattacharyya DK, Bandyopadhyay S (1998) Effect of mustard meal on the production of arachidonic acid by Mortierella elongata SC-208. J Am Oil Chem Soc 75(8):1053–1055Google Scholar
- 12.Jang H-D, Lin Y-Y, Yang S-S (2000) Polyunsaturated fatty acid production with Mortierella alpina by solid substrate fermentation. Bot Bull Acad Sinica 41(1):41–48Google Scholar
- 16.Voigt K (2012) Zygomycota. In: Frey W (ed) Syllabus of plant families—A. Engler’s Syllabus der Pflanzenfamilien part 1/1: blue-green algae, Myxomycetes and Myxomycete-like organisms, phytoparasitic protists, heterotrophic heterokontobionta and fungi p.p. Borntraeger, Stuttgart, pp 130–162.Google Scholar
- 35.Samek O, Zemánek P, Bernatov S, Pilát Z, Telle HH (2012) Following lipids in the food chain: determination of the iodine value using Raman micro-spectroscopy. Spectrosc Eur 24(3):22–25Google Scholar
- 39.Folch J, Lees M, Sloane Stanley GH (1957) A simple method for the isolation and purification of total lipides from animal tissues. J Biol Chem 226(1):497–509Google Scholar
- 41.Schimek C, Wöstemeyer J (2005) Pheromone action in the fungal groups Chytridiomycota, and Zygomycota, and in the Oomycota. In: Esser K (ed) The Mycota I: growth, differentiation and sexuality, vol 1. The Mycota, 2nd edn. Springer, HeidelbergGoogle Scholar
- 42.Gooday GW (1994) Hormones in mycelial fungi. In: Wessels JH, Meinhardt F (eds) Growth, differentiation and sexuality, vol 1. The Mycota. Springer Berlin Heidelberg, pp 401–411Google Scholar