[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.

[Inhibition of Candida valida growth by copper ions]. / Ingibirovanie rosta Candida valida ionami medi.

The high toxicity of copper ions for Candida valida growth was established at pH-auxostat regime. The value of mu max decreased even at the residual Cu2+ concentration 1.0 mg/l. The inhibition constant (Ki) that characterized a copper ion concentration at which yeast specific growth rate was halved was equal to 7.7 mg/l. A linear dependence of 1/mu max on a residual concentration of copper ions indicates that yeast growth inhibition is due to inhibition of one enzymic reaction which is the most sensitive to copper. Yeast growth inhibition by copper was accompanied by accumulation of Cu2+ ions in biomass, a decrease in nucleic acid and true protein contents, and changes in amino acid composition of protein. The amounts of cystine and cysteine in protein increased and tryptophane content decreased with inhibition of yeast growth. Yeast growth inhibition by copper did not affect the lipid content but significantly reduced the degree of unsaturation due to a decrease in the amounts of polyunsaturated linoleic and alpha-linolenic acids.

[Relation between cyanide-resistant respiration, effectiveness and rate of growth of Candida valida on ethanol]. / Issledovanie vzaimosviazi mezhdu tsianidrezistentnym dykhaniem, éffektivnost'iu i skorost'iu rosta Candida valida na étanole.

The object of this work was to study the correlation between the growth rate of Candida valida and its cyanide-resistant respiration, as well as to investigate the effect of cyanide-resistant oxidase on biomass yield in the course of continuous cultivation of the yeast. The inhibition of cellular respiration by cyanide was shown to be directly correlated with the biomass yield. The intensity of cyanide-resistant respiration depended on the growth rate of the culture, and was lowest at the highest growth rates. It has been concluded that, when cyanide-resistant oxidase appears in the yeast cells, it functions simultaneously with the main respiratory chain. Cyanide-resistant respiration can be inhibited under the optimal conditions of the culture growth.

[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.