in a prior art reactor set up dense aggregates of microorganisms are formed , typically in or embedded in an extracellular matrix . such may relate to granules , to sphere like entities having a higher viscosity than water , globules , a biofilm , etc . the dense aggregates comprise extracellular polymeric substances , or biopolymers , in particular linear polysaccharides . the present invention is in the field of extraction of a biopolymer from a granular sludge , a biopolymer obtained by such method , and a use of such method .