[Influence of lignin and oxygen on the growth and the lipid formation of the fungus Lentinus tigrinus].

During cultivation of the filamentous fungus Lentinus tigrinus on a medium containing lignin, a high oxygen content stimulated the growth of the fungus and contributed to the yield of lipids. A high content of phosphatidic acid and a reduction in the level of phosphatidylethanolamine and phosphatidylserine were first detected in the composition of phospholipids. Changes in the composition of neutral lipids, such as variation in the ratio of esterified and free sterols, have occurred; thus, the amount of sterol esters reduced simultaneously with a decrease in the content of free fatty acids. Based on the obtained results, the possible role of phosphatidic acid as a second messenger in the process of the consumption of lignin by the fungus Lentinus tigrinus is discussed.

[Biodiesel fuel production from lipids of filamentous fungi].

The main stages in the production of biodiesel fuel from lipids of filamentous fungi belonging to the order Mucorales are described. Fungi of the family Cunninghamellaceae have been screened; the lipogenic activity of the examined strains has been assessed; and a producer generating up to 50% of lipids, represented by triacylglycerols, has been found. The substitution effect of a source of carbon and nitrogen with less expensive components (in particular, various industrial wastes) has been studied, as well as their influence on the quantity and major characteristics of the final product. An ecologically friendly method for extracting lipids from fungal mycelia, utilizing supercritical technologies, has been used. A correlation between the lipid content in the spore inoculum and the maximal lipid content in biomass has been discovered; this correlation is proposed for optimizing the biotechnology and increasing the yield of final products.

[Effects of conditions for obtaining sporangiospores of the inoculum on the morphology and productivity of the fungus Mucor circinelloides var. lusitanicus 12 M, a producer of gamma-linolenic acid].

Effects of lipid composition of sporangiospores of the fungus Mucor circinelloides var. lusitanicus 12 M, obtained within diverse time frames using distinct nutritive media, on the morphology of the fungus in submerged cultures, the yield of the biomass, and its content of gamma-linolenic acid have been studied. The levels of base phospholipids and individual fractions of neutral lipids in sporangiospores were correlated with the character of their germination. The spores characterized by a high rate of germination and giving rise to a well-developed mycelium contained more phosphatidylcholine and phosphatidylserine, but the level of diacylglycerols was low. An increase in diacylglycerols, free fatty acids, and sterols in lipids of sporangiospores of the inoculate was associated with deterioration of the mycelium development, dimorphism, and lowering of the yield of the biomass of the fungus.

[Activity of NAD-dependent isocitrate dehydrogenase, isocitrate lyase, and malate dehydrogenase in Mucor circinelloides var. lusitanicus INMI under different modes of nitrogen supply].

The growth and morphology as well as lipogenesis and activity of the enzymes of the tricarboxylic acid cycle and the glyoxylate cycle were studied in the fungus Mucor circinelloides var. lusitanicus INMI grown at various concentrations of urea (nitrogen source) added to the medium in different modes. It was shown that the maximum lipid content in the biomass was observed at a low (0.5 g/l) concentration of the nitrogen source, whereas the highest content of gamma-linolenic acid in the lipids was detected at high (up to 4.0 g/l) concentrations of the nitrogen source. It was found that, when the feed-batch mode of nitrogen supply was used, the amount of gamma-linolenic acid in total fatty acids was higher (up to 35%) than in the case of a single administration of the same amount of nitrogen source to the medium. The differences in the fatty acid composition and the unsaturation degree of the lipids from different subcellular fractions were demonstrated. The mycelium from the culture grown after a single administration of the nitrogen source was deformed to a great extent. The activities of the TCA cycle enzymes, NAD-dependent isocitrate dehydrogenase (IDH), and malate dehydrogenase (MDH) were lower than in the case of the feed-batch mode of urea addition, whereas the activity of isocitrate lyase (ICL), the key enzyme of the glyoxylate cycle, was higher. The coupling of the cell metabolism and the lipid composition of fungal cells and the process of cell differentiation in fungi depending on the conditions of nitrogen supply is discussed.

[Metabolic characteristics and lipid composition of yeastlike cells and mycelium of Mucor circinelloides var. lusitanicus INMI grown at a high glucose content in the medium].

It is shown that the fungus Mucor circinelloides var. lusitanicus INMI grown under aerobic conditions in a medium with a high glucose concentration (20%) is capable of both yeastlike and mycelial growth. In the mycelium, the activity of NAD-dependent isocitrate dehydrogenase was more than twice as high as in yeastlike cells, whereas the isocitrate lyase activity was lower. A number of significant differences were found in the lipid composition of the cells of two different morphological variants. Yeastlike cells contained more polar lipids and free fatty acids and less principal reserve lipids (triacylglycerides) than mycelial cells; the content of gamma-linolenic acid and the degree of lipid unsaturation were significantly lower in these cells than in the mycelium. In yeastlike cells, glycolipids composed the bulk of polar lipids; the proportion of phospholipids (primarily phosphatidylserine, phosphatidylcholine, phosphatidylethanolamine, and cardiolipin) was lower. The relationship between cellular metabolism and the lipid composition of fungal cells of different morphotypes grown at high concentrations of glucose, one of the main inducers of dimorphic growth, is discussed.

[Sporangiospore lipids of the mycelial fungus Mucor ramannianus incapable of dimorphic growth].

Members of the species Mucor ramannianus are believed to be monomorphic. They grow only as a mycelium and are not capable of growth as budding cells, i.e., of dimorphic growth. In our study, we investigated the lipid composition of M. ramannianus sporangiospores, which retained the capability of initiating mycelial growth in the course of long-term cultivation of the spore-forming mycelium. It was demonstrated that sporangiospores contained high concentrations of triacylglycerides (TAG) in their reserve lipids and high concentrations of phosphatidylcholine (PC) in their membrane lipids; low concentrations of methylated ergosterol precursors were detected among sterols. On the basis of the data presented, in order to evaluate the potential of mucor fungi for yeastlike growth, it has been suggested to analyze the qualitative and quantitative characteristics of their sporangiospore lipids and to consider the following criteria as the criteria of sporangiospore capacity for giving rise to yeastlike growth upon spore germination: (1) the phosphatidylethanolamine/phosphatidylcholine (PE/PC) ratio; (2) the level of ergosterol and the ratio between the methylated and demethylated sterols; as well as (3) the ratios between phospholipids and glycolipids (PL/GL) and (4) between etherified and free sterols (ES/FS).

[The role of sterols in morphogenetic processes and dimorphism in fungi].

The review considers the fundamental biological problem of fungal dimorphism as an adaptive reaction to adverse impacts. Primary attention is paid to sterols, phospholipids, storage lipids, and fatty acids. The structural and biological functions of sterols are considered, as well as their role in membrane stabilization under stress and their relation to morphogenetic processes in mycelial fungi, of which many are pathogenic. Data on the biosynthesis of the main fungal sterol, ergosterol, are presented, as well as data on the inhibitors of this process and on the mutants deficient in its particular stages. Ergosterol biosynthesis is also considered in terms of its relation to the composition of the fungal cell wall, which is the cell shape-determining structure, and to the intensity of chitin synthesis, a process in which azole derivatives play a role. Data obtained by the authors are presented that show the role of changes in the composition of sterols, phospholipids, storage lipids, and unsaturated fatty acids of resting cells in the induction of yeastlike growth in mucoraceous fungi.

[Utilization of H2O2 as the oxygen source by bacteria of the genera Pseudomonas and Rhodococcus]. / Ispol'zovanie H2O2 v kachestve istochnika kisloroda bakteriiami rodov Pseudomonas i Rhodococcus.

The growth of bacteria of the genera Pseudomonas and Rhodococcus in the presence of hydrogen peroxide as the sole source of oxygen was studied. The toxic effect of H2O2 in the concentration range of 100-200 microg/ml was shown to extend the lag phase by 2 to 3 days. Apart from the peroxide toxicity, the bacterial growth was inhibited by the toxic effect of dissolved oxygen in concentrations over 100 microg O2/ml; in the presence of a liquid hydrocarbon phase, this effect was alleviated. Under decreased partial pressure of oxygen in the presence of hydrocarbons (12-15 vol %), the culture growth was initiated at high initial concentrations of H2O2 (300 microg/ml). When hydrogen peroxide concentrations exceeded 320 microg/ml, no growth occurred, no matter how much hydrocarbon was added.

[Changes in the lipid composition of Mucor hiemalis sporangiospores related to the age of the spore-forming culture]. / Izmenenie sostava lipidov sporangiospor Mucor hiemalis v sviazi s vozrastom sporogennoi kul'tury.

Analysis of sporangiospore lipids of the fungus Mucor hiemalis F-1156 showed that alterations occur in the content of fatty acids and individual classes of lipids during long-term cultivation (for about 20 days). The changes in the lipid composition related to the age of the spore-forming mycelium suggest an important role of sporangiospore lipids in spore germination and in further development of the spherical cells formed in this processes. The M. hiemalis F-1156 sporangiospores with a lipid pool exhausted during long-term cultivation can give rise to both mycelial and yeastlike growth.

[Sporangiospores of the fungus Mucor lusitanicus 12M: correlation between lipid composition, viability, and morphology of growth upon germination]. / Korreliatsiia mezhdu lipidnym sostavom sporangiospor, ikh zhiznesposobnost'iu i morfologiei kletochnogo rosta griba Mucor lusitanicus 12M.

We studied viability of sporangiospores from a surface culture of the fungus Mucor lusitanicus 12M grown on wheat bran. With culture ageing, the sporangiospores exhibited a tendency toward dimorphic growth upon germination and then lost the ability to germinate. This correlated with changes in the sporangiospore lipid composition, which involved a reduction in the total lipid pool and in the levels of reserve lipids and phospholipids in particular. We suggest that lipid catabolism in sporangiospores causes their defectiveness in the senescent culture.

[Sterols of the fungus Mucor hiemalis sporangiospores]. / Steriny sporangiospor griba Mucor hiemalis.

We earlier reported that the viability and lipid composition of Mucor hiemalis F-1156 sporangiospores, as well as their capacity to develop yeast-like cells, depend on the age of the spore-forming culture [1]. With the increase in the time of the culture growth, sporangiospores exhibit a decrease in the levels of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, cardiolipin, and reserve lipids, as well as in the degree of fatty acid unsaturation, whereas the level of glycolipids increases. However, sterol composition was not been studied. Sterols are involved in morphogenetic processes [2, 3], and therefore we suggested that sporangiospores from senescent cultures, which, upon germination, develop mycelium and yeast-like cells, may exhibit a distinctive sterol pattern, along with the changed composition of fatty acids and polar and neutral lipids.

[Synthesis of biologically active lipids by fungus Mucor lusitanicus 306D grown on media with various composition]. / Sintez biologicheski aktivnykh lipidov gribom Mucor lusitanicus 306D na sredakh raznogo sostava.

Growth and lipogenesis of fungus Mucor lusitanicus 306 D producing gamma-linolenic acid was studied under various regimes of nitrogen and carbon nutrition. Media containing food industry wastes such as maize extract, molasses, and protein hydrolysate were used. Content of gamma-linolenic acid was higher when using carbohydrates such as glucose and molasses as carbon sources and urea as a nitrogen source. At high glucose concentration (100 g/l), fed batch cultivation provided high content of gamma-linolenic acid in lipids (1 g/l). After extraction of lipids, fungus biomass contained 42% proteins with all essential amino acids. Defatted biomass was shown to be effectively assimilated by minks.

[Composition of sterols from arthrospores and mycelia of the fungus Mucor hiemalis]. / Sostav sterinov artrospor i mitseliia griba Mucor hiemalis.

Sterol composition of the arthrospores and mycelium of the fungus Mucor hiemalis 1156 was studied by the method of chromatography-mass spectrometry. Along with ergosterol, the major sterol of the culture studied, ten minor sterol were identified, which were either precursors or products of ergosterol degradation. The content of individual sterols differed substantially in arthrospores and mycelium, which represent different stages of ontogenetic development of the fungus. In arthrospores, the content of ergosterol was lower than in mycelium (55.9 and 78%, respectively). Among the precursors of ergosterol, methylated sterols predominated in arthrospores (24.1% versus 11.6% in mycelium). Eburicol and 4,4-dimethylfecosterol were the major methylated sterols of arthrospores (10.6 and 8.1%, respectively). In addition, two uncommon and extremely rare sterols, 1-dihydro-dehydroneoergosterol and dehydroneoergosterol, were identified (for the first time in M. hiemalis). These substances, containing a complex system of conjugated double bonds in their A and B rings, are the products of ergosterol degradation. The data on sterol composition are discussed in terms of their morphogenetic implication.