Encapsulation of bacteria in silica gels

Escherichia roll cells have been encapsulated within sol-gel silica matrices. The cellular organization of these bacteria appears to be well preserved. Their beta-galactosidase activity was measured via the hydrolysis of p-NPG. The formation of p-nitrophenol was followed by optical absorption. These experiments show that the enzymatic activity of entrapped cells still exhibit a Michaelis behaviour. Their affinity toward the p-NPG substrate seems even better when the cells are trapped. They can be kept for days in wet gels but their activity decreases drastically upon drying. (C) 1999 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.