Gelatin membrane filter

In-process verification of the sterility of filtered gases may be done by constantly bleeding off a trickle of gas through a pressure reducer on the downstream side of the sterilizing filter. The bleed may be filtered through a gelatin membrane, which should be removed daily or at other suitable intervals for incubation and examination for evidence of microbiological contamination. 

Specific cake resistance a ranges from 10 m/kg for easily filtered large particles to lo m/kg for gelatinous cakes. The membrane resistance Rp typically equals 10 to lO" m. Both a and Rp depend on the filtering pressure. 

Analytically important enzymes present in microbial cells may often be utilized without further purification. The cells are easily harvested and immobilized on the surface of a sensor by a simple attachment using dialysis membrane, entrapment into gel (agar, collagen, gelatin, etc.) layers, adsorption on filter paper or other supports and only rarely covalently bound. Riedel [186] gives in his review paper characteristics... 

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