PURPOSE: To provide a soln. for accelerative recovery of petroleum containing polysaccharides having a main chain composed of a pyranose or furanose unit and having thickening power by regulating a compsn. based on homopolysaccharides being a raw material to a high pH value and subsequently heat-treating this compsn. to separate the soln.

CONSTITUTION: Sclerotium rolfsii is cultured and fermented in a culture medium containing glucose as a carbon source and an yeast extract as an org. nitrogen source to obtain a fermentation completed soln. with pH 6 containing homopolysaccharide such as screloglucan. Next, caustic soda is added to the compsn. based on this homopolysaccharide being a raw material to regulate the pH of the compsn. to a value higher than 9 and this comps. is heat-treated to be centrifugally separated to separate a soln. to obtain a soln. based on non-crosslinkable homosaccharide formed from a homopolymer main chain composed of a pyranose or furanose unit having a side chain containing the same pyranose or furanose unit and grafted or not grafted to the main chain.