Heavy ion mutagenesis combined with triclosan screening provides a new strategy for improving the arachidonic acid yield in Mortierella alpina.

BACKGROUND: Arachidonic acid (ARA), which is a ω-6 polyunsaturated fatty acid, has a wide range of biological activities and is an essential component of cellular membranes in some human tissues. Mortierella alpina is the best strain for industrial production of ARA. To increase its yield of arachidonic acid, heavy ion beam irradiation mutagenesis of Mortierella alpina was carried out in combination with triclosan and octyl gallate treatment. RESULTS: The obtained mutant strain F-23 ultimately achieved an ARA yield of 5.26 g L- 1, which is 3.24 times higher than that of the wild-type strain. In addition, quantitative real-time PCR confirmed that the expression levels of fatty acid synthase (FAS), Δ5-desaturase, Δ6-desaturase, and Δ9-desaturase were all significantly up-regulated in the mutant F-23 strain, especially Δ6- and Δ9-desaturase, which were up-regulated 3- and 2-fold, respectively. CONCLUSIONS: This study confirmed a feasible mutagenesis breeding strategy for improving ARA production and provided a mutant of Mortierella alpina with high ARA yield.

[Screening of high-yield PUFAs Mortierella isabellina strain].

The original strain Mortierella isabellina As3.3410 was treated by microwave and ultraviolet. Mutated strains were screened by acetyl salicylic acid and low temperature (15°C). A high-yield strain named as A35-4 was successfully selected. The biomass of this strain was 17.9 g/L, oil content was 67.8%, oil production was 12.12 g/L, polyunsaturated fatty acids (PUFAs) content was 20.2%, and production of PUFAs was 2.46 g/L, which increased 32.6%, 49.8%, 98.69%, 14.0%, and 125.7% compared with the original A0 stain, respectively. The continuous slope transmission experiments confirmed that the strain had a good genetic stability. The study is beneficial for cloning high efficiency genes for PUFAs and producing PUFAs in this stain, and lays the ground work for creation of transgenic plants containing high levels of PUFAs.

[Comparative analysis of radial linear growth velocity of micromycetes isolated from different ecotopes]. / Sravnitel'nyi analiz skorosti radial'nogo rosta mikromitsetov, vydelennykh iz razlichnykh ékotopov.

The work aim was the discovering of peculiarities of microscopic fungi responding to radioactive pollution by growth velocity change. The linear growth velocity of a broad range of micromycetes was analyzed. They were chosen in such a way that every species, as far as possible, was presented by the strains isolated from radioactive polluted and clean regions. Most of the studied species were characterized by the absence of reliable growth velocity differences of strains of the same species growing on rich and starving media. Only two species--Aureobasidium pullulans and Penicillium spinulosum were the exception. Their growth velocities on malt-agar were much more then those on starving medium (1.7-3.6. times). Species Hormonema dematioides did not have reliable differences of growth velocity on optimal and starving media, but A. pullulans had this difference (2.3-3.6 times). It is supposed to use this observation to simplify identification of these species. Only strains within species Cladosporium sphaerospermum and especially P. funiculosum isolated from radioactive polluted ecotopes had growth velocity which was less then that of the strains from clean regions. The delay of growth velocity in such conditions can testify to adaptive change of metabolic processes of these strains. The strains which were characterized by delay of growth velocity existed at the substrates with high radioactive pollution for a long time.