NOVELTY - Producing lipids from biomass including polysaccharide, comprises subjecting the biomass including polysaccharide to hydrolysis; preparing an inoculum comprising oleaginous microorganism in a first fermentation device; feeding the first aqueous phase and the first fermentation broth to a second fermentation device; subjecting the second fermentation broth to separation to obtain an aqueous suspension of oleaginous cellular biomass comprising lipids and a second aqueous phase; subjecting second aqueous phase to reverse osmosis; and feeding retentate to the first fermentation device.    USE - The process is useful for producing lipids from biomass including at least one polysaccharide (claimed). The lipids can be used in the production of biodiesel or green diesel which can be used as such, or in a mixture with other automotive fuels.    ADVANTAGE - The process allows lipids to be obtained with a high yield (e.g. a yield of lipids with respect to the total quantity of sugars used for the fermentation higher than or equal to 25%, the yield to lipids being calculated as grams of lipids obtained per gram of sugar used for the fermentation).    DETAILED DESCRIPTION - Producing lipids from biomass including at least one polysaccharide, comprises subjecting the biomass including at least one polysaccharide to hydrolysis to obtain a mixture comprising a first solid phase and a first aqueous phase; preparing an inoculum comprising at least one oleaginous microorganism in a first fermentation device to obtain first fermentation broth; feeding the first aqueous phase and the first fermentation broth to a second fermentation device to obtain a second fermentation broth; subjecting the second fermentation broth to separation for obtaining an aqueous suspension of oleaginous cellular biomass comprising lipids and a second aqueous phase; subjecting the second aqueous phase to reverse osmosis for obtaining a permeate and a retentate; and feeding the retentate to the first fermentation device or to the second fermentation device, preferably to the first fermentation device.