The purpose of the present invention is to provide a process for protection of enzymatic biocatalysts, constituted by a primary support, wrapped by a secondary matrix. More particularly, the invention is embodied as a bioreactor with a configuration that preserves the physical integrity and catalytic activity of the biocatalyst after long runs, and at the same time allows an easy separation of the protected biocatalyst from the solid, precipitated during the reaction course. Still more particularly, the invention refers to the use of the bioreactor herein described for the enzymatic synthesis of .beta.-lactam antibiotics, including the insoluble enzymatic catalysts, which have a primary matrix for immobilization involved by a secondary matrix, which is able to preserve 100% of the catalyst physical integrity and approximately 100% of its catalytic activity.