A method and apparatus for enzymatic hydrolysis where a plant based feed is hydrolysed using an enzyme to form a hydrolysed product. An additive for preventing enzyme adsorption is fed to an enzymatic hydrolysis stage, the plant based feed the hydrolysed product a starting material, and/or a plant based material formed from the starting material. The hydrolysed product is supplied from the enzymatic hydrolysis stage to a first solid-liquid separation stage where a lignin fraction comprising the additive and a liquid composition comprising the enzyme are separated. The liquid composition is mixed with the plant based material in a mixing stage, forming a mixture. A solid fraction and liquid fraction are separated from the mixture in a second solid-liquid separation stage. At least part of the solid which comprises comprising the enzyme is fed as the plant based feed to the enzymatic hydrolysis stage.