Controlling the hydration of covalently immobilised penicillin G amidase in low-water medium: properties and use of Celite R-640

The study describes how Celite R-640 adsorbs liquid water in toluene and vapour water from a gas phase. In toluene, Celite R-640 is able to maintain the water activity (aw) constant within broad ranges of water concentrations. The aw values are strongly related to the original hydration of the Celite batches, but prolonged drying confers comparable and reproducible properties to the different batches. The use of Celite R-640 in controlling the hydration and activity of covalently immobilised PGA in toluene is reported.