Abstract: A method is provided for preparing a water-insoluble lignosulfonate polymer from a first solution containing lignosulfonate precursors, which involves a) separating the lignosulfonate precursors from the first solution and providing a second solution with at least 5 wt % of lignosulfonate precursors obtained from the first solution, wherein the separating comprises filtering out components with a predefined particle diameter and separating low-molecular weight components including salts and low-molecular organic compounds, b) adding a radical-forming enzyme and gas to the second solution, wherein the gas comprises oxygen, and c) polymerizing the lignosulfonate precursors of the resultant solution of b). Other related aspects are described and claimed.