Identification and Characterisation of an Oleaginous Fungus Producing High g-Linoleneic Acid

Abstract

Oleaginous fungi serve as good alternatives for the production of essential, polyunsaturated fatty acids (PUFA) such as glinolenic acid (GLA; 18:3). In this study, a locally isolated fungus, isolate 2A1, was evaluated for its lipid and GLA production, and its identity was determined. The fungus was grown in nitrogen-limited media and the amount of lipid and GLA produced were determined every 12 hours. The highest percentage of lipid produced per cell dry weight was 38.64% (w/w) while the highest amount of GLA produced was 0.65 g/L. These observations indicate that isolate 2A1 is a good lipid producer and capable of accumulating high amounts of GLA. To identify isolate 2A1 to the species level, its morphology was observed under the light and electron microscope. Subsequently, its 18S rDNA and the internal transcribed spacer (ITS) sequences were cloned, sequenced and analysed phylogenetically to 18S rDNA and ITS1 sequences of related fungi. Microscopic observation showed that isolate 2A1 produced coenocytic hyphae and self-bearing globose sporangioles, with a diameter between 6-8 μm. Neighbour-joining tree built based on the 1.6 kb 18S rDNA region clustered isolate 2A1 with fungi of the genus Cunninghamella. Maximum parsimony tree analysis based on a 154 bp ITS1 sequence grouped isolate 2A1 together with Cunninghamella bainieri strain NRRL 1375 with 100% bootstrap value. Thus, based on morphological and molecular phylogenetic data, isolate 2A1 is designated as C. baineri strain 2A1.