[Biosynthesis of arachidonic acid by micromycetes (review)].

Arachidonic acid (ARA, 5,8,11,14-cis-eicosatetraenoic acid) is widely used in medicine, pharmaceutics, cosmetics, dietary nutrition, agriculture, and other fields. Microbiological production of ARA is of increased interest since the natural sources (pig liver, adrenal glands, and egg-yolk) cannot satisfy its growing requirements. Mechanisms for ARA biosynthesis as well as the regulation of enzymes involved in this process are considered. Review summarizes literature data concerning individual stages of microbiological ARA production, methods for screening of active strains-producers, physiological regulation of ARA synthesis in micromycetes (the effect of growth phase, medium composition, pH, temperature, and aeration), and effective technologies of fermentation and the product recovery. Information on the whole biotechnological process from strain selection to the ARA yield improvement and purification of the end product is presented.

[Bacterial strain characterizing by EDTA requirement].

A novel strain of bacteria (LPM-4) was isolated that is characterized by a unique EDTA requirement for cell growth. Suspensions of washed cells of strain LPM-4 degrated EDTA complexes with Ba2+, Mg 2+, Ca2+, and Mn2+ at constant rates (0.310-0.486 mmol EDTA/(g h)) and Zn-EDTA at an initial rate of 0.137 +/- 0.016 mmol EDTA/(g h). The temperature optima for cell growth and EDTA degradation were determined under pH-auxostat cultivation. As compared with the known EDTA-degrating bacteria, strain LPM-4 exhibited a higher specific growth rate (0.095 h(-1)) and lower mass cell yield (0.219 g cells/g EDTA) that is promising for its practical applications for EDTA removal in wastewater treatment plants.

[Bacterial degradation of EDTA]. / Issledovanie bakterial'noi degradatsii EDTA.

Degradation of EDTA (ethylenediaminetetraacetic acid) or metal-EDTA complexes by cell suspensions of the bacterial strain DSM 9103 was studied. The activity of EDTA degradation was the highest in the phase of active cell growth and decreased considerably in the stationary phase, after substrate depletion in the medium. Exponential-phase cells were incubated in HEPES buffer (pH 7.0) with 1 mM of uncomplexed EDTA or EDTA complexes with Mg2+, Ca2+, Mn2+, Pb2+, Co2+, Cd2+, Zn2+, Cu2+, or Fe3+. The metal-EDTA complexes (Me-EDTA) studied could be divided into three groups according to their degradability. EDTA complexes with stability constants K below 10(16) (lg K < 16), such as Mg-EDTA, Ca-EDTA, and Mn-EDTA, as well as uncomplexed EDTA, were degraded by the cell suspensions at a constant rate to completion within 5-10 h of incubation. Me-EDTA complexes with lg K above 16 (Zn-EDTA, Co-EDTA, Pb-EDTA, and Cu-EDTA) were not completely degraded during a 24-hour incubation, which was possibly due to the toxic effect of the metal ions released. No degradation of Cd-EDTA or Fe(III)-EDTA by cell suspensions of strain DSM 9103 was observed under the conditions studied.

[Growth-coupled lipid synthesis in Mortierella alpina LPM 301, a producer of arachidonic acid]. / Sopriazhennyi s rostom sintez lipidov u produtsenta arakhidonovoi kisloty Mortierella alpina LPM-301.

Mortierella alpina LPM 301, a producer of arachidonic acid (ARA), was found to possess a unique property of intense lipid synthesis in the period of active mycelium growth. Under batch cultivation of this strain in glucose-containing media with potassium nitrate or urea, the bulk of lipids (28-35% of dry biomass) was produced at the end of the exponential growth phase and remained almost unaltered in the stationary phase. The ARA content of lipids comprised 42-50% at the beginning of the stationary phase and increased continuously after glucose depletion in the medium due to the turnover of intracellular fatty acids; by the end of fermentation (189-210 h), the amount of ARA reached 46-60% of the total fatty acids (16-19% of dry mycelium). Plausible regulatory mechanisms of the growth-coupled lipid synthesis in microorganisms are discussed.

[Effect of conditions od Trichosporon pullulans culturing on the synthesis of immunomodulating glycoprotein]. / Vliianie usloviu kul'tivirovaniia Trichosporon pullulans na sintez glikoproteina-immunomoduliatora.

An extracellular glycoprotein (GP) exhibiting immunomodulating activity produced by the yeast Trichosporon pullulans grown in a defined ethanol-containing medium differed substantially in its composition from that of the yeast cell walls: therefore, it cannot be considered a structural component of the cell walls. In batch culture, the greatest GP production (40 mg/l) occurred in the exponential phase of the yeast growth. Under continuous cultivation, in both chemostat and pH-auxostat regimes, the specific rate of GP synthesis (qGP) increased with the increasing specific growth rate (mu) and reached 1.55 mg/(g h) at mumax. Under limitation of the yeast growth by zinc qGP was three times lower than under nitrogen or iron limitation. The rate of GP production depended inversely on the oxygen concentration.

[Microorganisms as potential producers of essential fatty acids]. / Mikroorganizmy kak potentsial'nye produtsenty nezamenimykh zhirnykh kislot.

The data on the importance of essential fatty acids in a balanced diet have been considered. The ways of essential fatty acid synthesis in microorganisms and their metabolism in animal tissues are being discussed. The criteria for microorganisms selection--producers of food lipids have been proposed.

[Effect of the growth rate on the biomass composition of Candida valida]. / Vliianie skorosti rosta na sostav biomassy u Candida valida.

The effect of growth rate on the biomass composition was studied with a thermotolerant strain of the yeast Candida valida grown in the chemostat at limitation of the growth by ethanol under the conditions of various temperature regimes. The temperature and the growth rate hardly influenced the content of protein and its amino acid composition. An increase in the specific growth rate of the cells caused a rise in the pool of free intracellular amino acids, in particular, glutamic acid. The degree of lipid unsaturation increased with a rise in the growth rate of the yeast as a result of intensification of oleic acid oxidative dehydration. As it had been shown earlier, the content of nucleic acids increased with a rise in the specific growth rate of the yeast.

[Biomass composition of thermotolerant yeasts of the genus Candida under elevated cultivation temperatures]. / Sostav biomassy termotolerantnykh drozhzhei roda Candida pri povyshennykh temperatureakh kul'tivirovaniia.

The effect of growth temperature on the content of nucleic acids, the content and composition of protein, and the pool of free amino acids and lipids was studied under the conditions of chemostat cultivation of yeast strains at constant flow rates and pO2. The pool of free amino acids in all of the strains decreased with an increase in the temperature of growth. Changes in the content and composition of other cellular components depending on temperature were determined by individual characteristics of the strains. A linear relationship between the content of biomass components and the temperature of growth was found only in Candida scottii. The temperature of yeast cultivation may be used as a factor regulating the pool of free intracellular amino acids and the fatty acids composition of lipids.

[Relationship between continuous cultivation conditions and the lipid composition of Hansenual polymorpha]. / Sostav lipidov Hansenula polymorpha v zavisimosti ot uslovii nepreryvnogo kul'tivirovaniia.

The effect of temperature, pH, and specific growth rate on the composition of fatty acids and lipid classes was studied in the thermotolerant yeast Hansenula polymorpha grown in the chemostat in a medium with methanol. The fatty acid composition of lipids was found to change depending on the conditions of cultivation: the degree of unsaturation of fatty acids increased when the growth temperature decreased; the proportion of linoleic acid in the lipids increased with the specific growth rate of the yeast and with the pH of the medium. The composition of lipid classes also depended on the cultivation conditions. Therefore, it is possible to find such a regime for cultivating the yeast that would be optimal for the accumulation of particular lipid classes.

[Changes in the composition of intracellular lipids and hydrocarbons in Candida tropicalis in the absence of growth]. / Izmenenie sostava vnutrikletochnykh lipidov i uglevodorodov Candida tropicalis pri otsutstvii rosta

The fatty acid composition of lipids and the composition of hydrocarbons were studied in Candida tropicalis cultivated on a medium with propionic acid and incubated in the conditions of starvation and on a medium containing glucose-1-6-14C but no nitrogen. Intracellular fatty acids with an odd number of carbon atoms were found to be easily metabolized by yeast cells. The content and composition of intracellular hydrocarbons were very labile and underwent intensive transformation caused by changes in the metabolism of the yeast cell.