Abstract: In a filter bed (11) for the solid/fluid separation of media which contain substances that attack or dissolve cellulose, for example cellulase-containing enzymes, a matrix comprising a fibrous material structure of polyolefin fibrid particles (12) which are matted and anchored in one another and which can additionally contain up to 20% by weight of narrower fibrid polyolefin fibres and/or polyolefin fibres that have a fibre length of up to 5 mm. and have just started to fibrillate, in order to strengthen the sheet formation of the matrix. The actual filter-active particles, in particular kieselguhr particles and/or perlite particles having grain sizes of 5 to 100 um., are embedded in the cellulose-free fiber matrix.