Filing Date: 2002-03-14.-- Priority Data: ES P200100618 (2001-03-16)The invention relates to the selection of a mushroom, Ophiostoma piceae, which secretes a commercial esterase. The invention also relates to the production and characterisation of the enzyme and the application tests carried out on synthetic process liquids and pulps representative of paper pulp production processes using hardwood and softwood. The results obtained demonstrate that the novel enzyme possesses great affinity and activity in relation to cholesterol linoleate, oleate, tributyrin and triolein, said enzyme being able to reduce the concentrations of sterol esters and triglycerides during the treatment of process liquids from the production of eucalyptus and pine pulps respectively.