TECHNOLOGY FOCUS - BIOLOGY - Preferred Conditions: The acid hydrolysis is carried out at 100-150 degrees C for 20 minutes to 6 hours. The fermentation is feed-batch fermentation carried out at 200-400 degrees C for 3-10 days. The biomass is subjected to preliminary grinding process, before subjecting to acid hydrolysis. The biomass is ground until the particles having diameter of 0.1-10 mm, preferably less than 1 mm are obtained. The content of biomass in the reaction mixture is 5-40 weight% with respect to total weight of the reaction mixture. The oleaginous cellular biomass is subjected to mechanical treatment carried out using French press cell at pressure of 20-50 Kpsi. The mechanically-treated oleaginous cellular biomass is subjected to centrifugation at rotational speed of 3000-9000 rpm for 5-30 minutes. An oily phase comprising lipids, an aqueous phase comprising traces of non-separated lipids and non-fermented sugars, and a wet solid phase comprising cellular debris and traces of non-separated lipids are obtained at the end of centrifugation process. The wet solid phase is conveyed to acid hydrolysis. The aqueous phase and/or wet solid phase are subjected to extraction with at least one solvent chosen from 3-10C aliphatic hydrocarbons, and mixture comprising 3-5C aliphatic alcohol and 3-10C aliphatic hydrocarbon. Preferred Components: The polysaccharide is chosen from cellulose, hemicellulose and their mixture. The biomass is lignocellulosic biomass chosen from products of cultures e.g. Miscanthus, millet and common cane, and its by-products, residues and wastes, products of agricultural cultivations, forestation and silviculture comprising wood, plants, residues and by-products of agricultural processing, forestation and silviculture, agri-foodstuffs by-products intended for human feeding or zootechnics, chemically untreated residues of paper industry, and waste products discharging from the differentiated collection of solid urban waste. The oleaginous yeast is chosen from Rhodotorula glutinis, R.gracilis, R.graminis, Lipomyces starkeyi, L.lipofer, Trigonopsis variabilis, Candida kefyr, C.curvata, C.lipolytica, Pichia stipitis and Torulopsis sp..    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The alkyl- or aryl-sulfonic acids have 9-15 carbon atoms, and are chosen from dodecyl sulfonic acid, para-toluene sulfonic acid, 1-naphthalene sulfonic acid, 2-naphthalene sulfonic acid and 1,5-naphthalene disulfonic acid. At least one organic acid is soluble in water and extractable by organic solvent which is insoluble in water, preferably para-toluene sulfonic acid, 2-naphthalene sulfonic acid and/or 1,5-naphthalene disulfonic acid. The halogenated carboxylic acid is 20C or more difluoroacetic acid, trifluoroacetic acid, dichloroacetic acid, trichloroacetic acid and/or perfluorooctanoic acid. The content of at least one organic acid in the aqueous solution is 0-5 weight% with respect to the total weight of aqueous solution. The primary solid phase comprises lignin and cellulose. The primary aqueous phase comprises at least one 5C or 6C sugar and at least one organic acid. At least one sugar is xylose. The primary mixture is subjected to extraction with organic solvent insoluble in water. The organic solvent insoluble in water is chosen from halogenated hydrocarbons such as methylene chloride, monochlorobenzene and dichlorobenzene, aromatic hydrocarbons such as toluene and xylene, and 4-6C aliphatic alcohols such as n-butanol and n-pentanol, preferably mixture of toluene and n-butanol. The organic solvent insoluble in water is evaporated to obtain secondary solid phase comprising at least one organic acid which is then reutilized for acid hydrolysis. The secondary solid phase comprises lignin. The secondary aqueous phase comprises at least one 5C or 6C sugar. The secondary aqueous phase comprises xylose, glucose and cellobiose.