A process for producing secondary metabolites of viable plant cells, including 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; (d) immobilizing the entrapped cells within the matrix with a reactive gas including a carrier gas saturated with volatile SiO2 or organic modified SiO2 precursors. The matrix may be a SiO2 or inorganic oxide matrices, in which the weight ratio between cell load and inorganic material ranges between 1x10-4 and 1x10-2. The immobilized cells are not released in solution over a period of 6 months and maintain their viability while producing secondary metabolites.