Microbial production of dihomo-γ-linolenic acid by Δ5-desaturase gene-disruptants of Mortierella alpina 1S-4

We constructed dihomo-γ-linolenic acid (DGLA)-producing strains with disruption of the Δ5-desaturase (Δ5ds) gene, which encodes a key enzyme catalyzing the bioconversion of DGLA to arachidonic acid (ARA), by efficient gene-targeting, using Δlig4 strain of Mortierella alpina 1S-4 as the host. In previous study, we had already identified and disrupted the lig4 gene encoding DNA ligase 4, which involves in non-homologous end joining, in M. alpina 1S-4, and the Δlig4 strain had showed efficient gene-targeting. In this study, the uracil auxotroph of Δlig4 strain was constructed, and then transformed for disruption of Δ5ds. The isolation of nine Δ5ds-disruptants out of 18 isolates indicated that the disruption efficiency was 50%. The ratio of DGLA among the total fatty acids of the Δ5ds-disruptants reached 40.1%; however, no ARA was detected. To our knowledge, this is the first study to report the construction of DGLA-producing transformants by using the efficient gene-targeting system in M. alpina 1S-4.