Isolation and identification of native lower fungi for polyunsaturated fatty acid (PUFA) production in Thailand, and the effect of carbon and nitrogen sources on growth and production

摘要

This research focuses on isolation and identification of polyunsaturated fatty acid (PUFA) producing fungi from natural sources of Thailand, followed by experimental designs for carbon and nitrogen utilizations of the potential strains. The results show that 8 and 16 isolates of lower fungi from freshwater and wet-fallen leaves, respectively, could produce PUFAs. Among these isolates, the NR06 that was isolated from wet-fallen leaves at Tad Ta Phu waterfall, Nakhon Ratchasrima province. They showed the highest level productions of both biomass (15.49±0.24 g×l-1) and total fatty acids (16.44±0.30%). The major essential fatty acid composition was found to be arachidonic acid (ARA; C20:4n6) (32.24±0.35%). The minors were linoleic acid (C18:2n6) (8.26±0.59%) and γ-linoleic acid (GLA; C18:3n6) (5.48±0.08%). Besides the morphological characterization, taxonomic identification by the 636 bp-ITS region sequencing and phylogenetic analysis were performed. It was demonstrated that the fungal isolate NR06 was classified in the closest species of Mortierella elongata with 99% similarity (GenBank accession no. KF181625). Statistically based experimental designs (Design Expert 7.1 software) were applied to the optimization of biomass and fatty acid production in the NR06 culture. Using the glucose as a carbon source, there was a significant effect on both biomass and ARA production (p-values < 0.0001), whereas using yeast extract as a nitrogen source affected only ARA production (p-value = 0.02). It was suggested that the NR06 isolate could be further optimized for an improvement as a potential ARA producing strain.