treatment of glass plates by the polycation chitosan allowed the adhesion of kluyveromyces lactis cbs 683 cells. a similar surface treatment was applied to a matrix made of insulation-glass fibers which is a potentially useful support due to its high surface area. a limited amount of cells was retained in the matrix not treated with chitosan: this was attributed to filtration effect. however, the amount retained was always much greater on the treated matrix. direct observation showed that no adhesion occurred on the untreated fibers, while complete coverage could be obtained on the treated fibers under a certain conditions, multiple layers of cells or flocks adhered to the supports, due to redissolution of chitosan and local cell flocculation. in situ permeabilization of the immobilized cells with various solvents was found to be effective in exposing the intracellur $beta$ -galactosidase (ec 3.2.1.23). experiments with several batch and continuous operations showed excellent performances for the hydrolysis of lactose solutions in buffer when compared to published data. (edited author abstract) 20 refs