EFFECTS OF LIPASES ON BIRCH EXTRACTIVES

Fresh birch and birch sulfate pulp were treated with commercial lipase s in order to study the hydrolysis of lipophilic esters which may be h armful in papermaking. Enzymatic treatments were performed on extracti ve-containing water suspensions obtained from birch powder, on fresh b irch powder and on birch sulfate pulp. Changes in the amounts of diffe rent esterified lipid compounds in the materials were analyzed by capi llary gas chromatography and mass spectrometry. The lipid composition of the suspension was similar to that commonly found in the extractive s isolated from birch with neutral organic solvents. The fatty acid es ters constitiuted the major lipid group in the suspension. About 80% o f these esters were hydrolyzed to the corresponding free acids by the lipases. Other types of esters were hydrolyzed to a lower extent. Extr actives in birch powder were less accessible to the lipase treatment t han those in the suspension. The amounts of fatty acid esters were dec reased by about 50%. Fatty acids and terpenoids were the major compoun d groups of birch sulfate pulp. The lipases were capable of hydrolyzin g almost all the esterified lipid groups in the pulp.