Abstract: Secondary metabolites of viable plant cells are produced with the cells immobilized in a porous inorganic support. Immobilization includes the steps of: (a) preparing a support comprising a substantially uniform and porous matrix of inorganic material having a tensile strength of at least 500 MPa; (b) introducing a culture of viable plant cells into the pores of said matrix; (c) entrapping the plant cells by coating the matrix with a sol or colloidal suspension not interfering with the cell viability; and (d) immobilizing the entrapped cells within the matrix with a reactive gas including a carrier gas saturated with volatile SiO.sub.2 or organic modified SiO.sub.2 precursors. The tensile strength may be provided by impregnating the matrix with a gelling solution of SiO.sub.2 precursor for increasing stiffness of the matrix. The matrix may be a SiO.sub.2 or inorganic oxide matrices, in which the weight ratio between cell load and inorganic matrix ranges between 1.times.10.sup.-4 and 1.times.10.sup.-2.