NOVELTY - Producing bio-oil from biomass including polysaccharide, by subjecting biomass to acid hydrolysis in the presence of aqueous solution of organic acid, obtaining first mixture comprising first solid phase and first aqueous phase, subjecting the first mixture to enzymatic hydrolysis to obtain second mixture comprising second solid phase and second aqueous phase, fermenting the second aqueous phase with oleaginous yeast, and subjecting the obtained aqueous suspension to thermal treatment to obtain oily phase comprising bio-oil and third aqueous phase.    USE - The method is useful for producing bio-oil from biomass including polysaccharide, preferably lignocellulosic biomass chosen from (i) crops expressly cultivated for energy use, comprising by-products, residues and waste of the cultures or processing of the cultures, (ii) products of agricultural cultivations, forestation and silviculture, comprising wood, plants, residues and by-products of agricultural processings, forestation and silviculture, (iii) agri-foodstuffs by-products for human or animal feeding, (iv) non-chemically treated residues from paper industry, and (v) waste from differentiated collection of solid urban waste (all claimed). The bio-oil is useful for production of biofuels useful for motor vehicles or generation of electric energy or heat.    ADVANTAGE - The high yield of pentose and hexose sugars during the process can be efficiently used as carbon source for oleaginous yeasts. The organic acids used in the process and aqueous suspension comprising cells of oleaginous yeast can be recycled. The formation of by-products is reduced.    DETAILED DESCRIPTION - Production of bio-oil from biomass including polysaccharide, involves subjecting biomass to acid hydrolysis in the presence of aqueous solution of at least one organic acid chosen from 7-20C alkyl or aryl sulfonic acids, and halogenated carboxylic acids at 80-160 degrees C, obtaining first mixture comprising first solid phase and first aqueous phase, subjecting the first mixture to enzymatic hydrolysis to obtain second mixture comprising second solid phase and second aqueous phase, subjecting the second aqueous phase to fermentation in the presence of at least one oleaginous yeast to obtain aqueous suspension comprising cells of the oleaginous yeast, and subjecting the aqueous suspension to thermal treatment to obtain oily phase comprising bio-oil and third aqueous phase. An INDEPENDENT CLAIM is included for bio-oil obtained by the above-cited method.