Enzymatic hydrolysis by Humicola lanuginosa lipase of poly(lactic acid)-poly(glycolic acid) monolayers

The enzymatic hydrolysis by Humicola lanuginosa lipase (HLL) of spread inso luble monolayers of poly (alpha-hydroxy acid)s with various molecular weigh ts and various lactic-glycolic molar ratios was studied using a barostat su rface balance. The interfacial hydrolysis under enzyme action leads to the progressive fragmentation of the polymer molecules. The appearance at the i nterface of charged insoluble fragments was detected by measuring the surfa ce potential, while the solubilization of the small soluble fragments was d etected by measuring the decrease in the surface area. The data obtained we re used to test the mode of fragmentation: either random or chain-end sciss ion. The catalytic specific activity of HLL was estimated in the framework of the random scission model and compared with the activities obtained for the hydrolysis of simple molecules of di- and tri-glycerides organized as m onolayers or emulsion.