[The effect of pH, aeration, and temperature on arachidonic acid synthesis by Mortierella alpina].

The effects of pH, aeration, and temperature on the growth of fungal strain Mortierella alpina LPM-301 and the synthesis of lipids and arachidonic acid in glycerol-containing medium were studied. Arachidonic acid production in the stationary growth phase was found to depend considerably on the pH value; it reached the optimum at pH 6.0 and was irreversibly inhibited at a pH of 3.0. The PO2 values in a range from 10 to 50% showed no marked effect on mycelium growth or the synthesis of lipids and arachidonic acid. The temperature optimum for arachidonic acid production was 20-22 degrees C. Under continuous cultivation, the amount of arachidonic acid reached 29.8% of lipids and 7.4% of biomass. The arachidonic acid yield from the glycerol consumed was 4.1% by mass and 8.8% by energy. It is suggested that arachidonic acid synthesis at an unfavorable pH and elevated temperatures was limited by the activity of A-12-desaturase and by the conversion of linoleic to arachidonic acid, respectively.

EDTA-dependent assimilation of glucose and organic acids by an EDTA-degrading bacterium.

Bacterial strain VKM B-2445 is characterized by ethylenediaminetetraacetate (EDTA) requirement for cell growth. This strain could not grow on glucose and organic acids as the sole sources of carbon and energy, but it was able to metabolize these substrates added to EDTA medium. EDTA initiated assimilation of glucose, succinate, fumarate, malate, and citrate and supplied nitrogen for the biomass production from these substrates. Utilization of primarily nongrowth substrates by strain VKM B-2445 started when EDTA was exhausted or at least considerably degraded.

Biosynthesis of citric and isocitric acids from ethanol by mutant Yarrowia lipolytica N 1 under continuous cultivation.

The effect of ethanol, zinc, and iron (Fe(2+) and Fe(3+)) concentration and of oxygen supply on cell growth and the production of citric acid (CA) and isocitric acid (ICA) from ethanol by mutant Yarrowia lipolytica N 1 was studied under continuous cultivation. The following peculiarities of Y. lipolytica metabolism were found: (1) intensive CA production occurred under yeast growth limitation by nitrogen; (2) inhibition of yeast growth by ethanol was accompanied by significant alterations in fatty acid composition of lipids; (3) the production of CA and ICA from ethanol required high concentrations of zinc and iron ions; (4) the intracellular iron concentration determined whether CA or ICA was predominantly formed; (5) the cell's requirement for oxygen depended on the intracellular iron concentration. The events taking place in the production of CA and ICA were evaluated through the activities of enzyme systems involved in the metabolism of ethanol and CA in this strain.

Arachidonic-acid production by species of Mortierella.

A growth-inhibiting, aspirin-containing medium was developed to select arachidonic-acid-(ARA)-producing Mortierella species and to determine the fatty-acid content of 87 Mortierella strains. ARA was detected in 66 strains from 33 species and its production may prove useful for systematic studies on Mortierella spp. The ARA content of the 66 producing strains tested ranged from 4% to 55% of total lipids. Most of the ARA-producing strains of Mortierella (59 strains) grown on potato/glucose/agar synthesized <20% ARA. Four strains produced between 20% and 25% ARA and three produced >40%. An inverse relationship was observed between ARA and oleic-acid contents.