L. A. Galanina

Lipids of filamentous fungi as a material for producing biodiesel fuel

Species of various filamentous fungus taxa were tested for ability to produce lipids suitable as a material for manufacturing biodiesel. The mucoralean fungus Cunninghamella japonica was found to be a promising lipid producer. The inexpensive medium for its growth developed in this study contained ammonium nitrate as a nitrogen source. With its use, up to 16 g/l biomass and over 7 g/l lipids was obtained. The fungal lipids were dominated by oleic acid. It constituted 50% of total fatty acids. The iodine index of the lipid fraction was 86.61. The heat of combustion of the lipids, 37.13 MJ/kg, was close to the value for rapeseed oil.

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.

Species composition of food-spoiling mycelial fungi

We investigated the composition of the microflora that spoils foodstuffs (the surface of hard cheeses and sausages) at agribusiness factories. Mycelial fungi, mostly ascomycetes of the order Eurotiales belonging to the genus Penicillium play the main role in spoiling food. Most representatives of these fungi are mesophiles and possess the capacity for utilizing nutrient substrates in surface and submerged cultures.

The effect of the preservative sorbic acid on the lipid composition of the ascomycete fungus Penicillium roqueforti Thom

The mechanism of action of potassium sorbate, a widely used food preservative on the lipid composition of the Ascomycete fungus Penicillium roqueforti, the main contaminant of cheese, was investigated. The inhibition of fungal growth by potassium sorbate was found to be associated with a change in the composition of phospholipids (a decrease in phosphatidylcholine content and an increase in phosphatidylethanolamine and phosphatidic acid content) and of neutral lipids (a decrease in the triacylglycerol and sterol content and an increase in the free fatty acid content). The fatty acid composition of fungal lipids also changed. A drastic decrease in the linoleic acid content occurred both in the total lipid fraction and in the triacylglycerol and total phospholipid fractions, whereas the oleic acid content increased correspondingly. This suggests that sorbic acid (SA) affects Δ12 desaturase activity, which controls the adaptive response of mycelial fungi to deleterious environmental factors.

Lipid synthesis by Geomyces pannorum under the impact of stress factors

Lipogenic activity and fatty acid composition of two strains of Geomyces pannorum were studied in the course of fungal growth. The strains were isolated from an Arctic cryopeg lens (VKM FW-2241) and from Central Russia (VKM F-3808). The adaptive reactions in both strains towards the temperature decreasing to 2°C involved intensification of the fatty acid desaturation. The degree of lipid unsaturation increased mainly due to a higher amount of α-linolenic acid (α-C18:3) especially in the case of strain VKM FW-2241. Elevated NaCl concentration in the medium enhanced the level of linoleic acid (C18:2) which apparently played a specific role in osmoprotection. Strain VKM FW-2241 was more tolerant to increased salinity than strain VKM F-3808. Almost complete inhibition of the growth of strains VKM F-3808 and VKM FW-2241 occurred at salinity of 10 and 20%, respectively; however, the viability of the strains was not affected. Under the combined effect of high salinity and hypothermia, the ratio between C18:2 and α-C18:3 acids was intermediate, indicating that these acids were involved in two adaptation mechanisms. The inhibition of fungal growth under stress was found to result in lipid overproduction. An increased pool of energy-rich lipids in fungi possibly contributes to their strategy of cell survival.

Biologically active lipids in fungi of the Pilobolaceae family

The synthesis of bioactive lipids in three species of lower mycelial fungi of the genus Pilaira, the family Pilobolaceae, has been studied. The pigmentation of these fungi was found to be determined by the presence of β-carotene in amounts of 14.8 (P. moreaui), 115.7 (P. caucasica), and 312.9 (P. anomala) µg/g. The fatty acid profiles of the fungi are distinguished by the presence of up to 50% essential fatty acids, which is typical of zygomycetes of the order Mucorales. The fungi grown in submerged cultures showed a correlation of the degree of unsaturation of total fatty acids and the contents of β-carotene.

A biotechnology for the production of new biodiesel fuel

A new biotechnology for the production of biodiesel fuel on the basis of the lipids of filamentous fungi has been developed. The oleaginous mucoralean fungus, which produces up to 47.0–50.0% of lipids similar to rapeseed oil in their composition, are used as a producer. The duration of the fermentation process at 27–28°C is 4–5 days. The main characteristics of the biodiesel fuel based on fungal lipids satisfy the requirements of the basic standards, in particular, EN14214. The possibilities for creating a wasteless closedcycle technology based on the production of biodiesel and chitin in a single fermentation, applying stimulators for the germination of fungal conidia to reduce the duration of fermentations, and using glycerin formed in the synthesis of methyl esters as a source of carbon in a fermentation medium, along with wood hydrolyzates and the wastes of certain food plants in the fermentation process, are shown.

Filamentous fungi’s cell-wall extraction at different stages of ontogenesis and exploration of their carbohydrate composition

Methods of obtaining cell walls (CW) for specimens of mucoraceous molds and ascomycetic affined fungi are developed at the stage of mycelium and resting cells, or spores. CW purity was assessed by electron microscopy, specific staining methods, scourage control, presence of ribose and desoxyribose, and the comparison of chitin content in whole cells and CW of fungi (a new criteria). The authors discuss the significance of the proposed methods of obtaining pure fractions of CW and of the study of their carbohydrate content for the chemotaxonomy of filamentous fungi.

Fatty Acids in the Species of Several Zygomycete Taxa

The composition of fatty acids synthesized de novo by thirty strains of zygomycetes from various taxa was studied. The qualitative fatty acid compositions of the fungal lipids were found to be virtually identical, but there were significant differences in the contents of individual acids. Highly active producers of essential C18 fatty acids, with their content exceeding 30–40% of total fatty acids, were discovered among the fungi of the families Mucoraceae, Pilobolaceae, and Radiomycetaceae. Linoleic acid was found to predominate in the fungi of the genera Radiomyces, Mycotypha, and Circinella, and linolenic acid (identified as its γ-isomer by gas-liquid chromatography), in the fungi of the genera Absidia, Circinella, Pilaira, and Hesseltinella. The total yield (mg/l) of bioactive acids (C18:3, C18:2, C18:1) varied from 761.4 in Pilaira anomala to 3477.9 in Syncephalastrum racemosum; the total yield of essential acids, from 520.7 in Pilaira anomala to 1154.5 in Hesseltinella vesiculosa; of linoleic acid, from 279.7 in Pilaira anomala to 836.3 in Mycotypha indica; and of linolenic acid, from 120.8 in Mycotypha indica to 708.0 in Hesseltinella vesiculosa. The data on the efficient synthesis of these acids make the actively producing strains promising for biotechnological synthesis of commercially valuable lipids. Linderina pennispora VKM F-1219, a zygomycete of the family Kickxellaceae, which was earlier singled out into the order Kickxellales, was shown to differ from zygomycetes of the order Mucorales in having a high content of cis-9-hexadecenoic (palmitoleic) acid, reaching 37.0% of the fatty acid total.

The prevalence of cis-9-hexadecenoic acid is a specific feature of the fatty acid profile of zygomycetes from the order Kickxellales

The fatty acid profiles of zygomycetes from the family Kickxellaceae of the order Kickxellales were studied with reference to the species Kicksella alabastrina of the key genus Kicksella of the family and the species Linderina pennispora. When synthesized de novo, the lipids of these species show the prevalence of cis-9-hexadecenoic acid. This trait is stable and does not depend on cultivation conditions and can, therefore, be considered as a specific chemotaxonomic characteristic of fungi from the order Kickxellales. The fatty acid profiles of the two fungi under study are similar to that of sea buckthorn oil.