Abstract: This invention relates to a process for the production of a polysaccharide wherein a microorganism species which produces polysaccharide (preferably in the stationary phase of the growth cycle) is supported on a porous, particulate inert support, the pore size being greater than about 0.5 .mu.m, to form an immobilized cell system, aqueous nutrient medium is passed through the immobilized system, and polysaccharide-containing medium is withdrawn from the system. The invention provides also for the use of the polysaccharide in the displacement of fluid from subsurface formations, and an immobilized cell system for use in the foregoing process.