Enzymatic hydrolysis by Humicola lanuginosa lipase of polycaprolactone monolayers

The enzymatic hydrolysis by Humicola lanuginosa lipase (HLL) of spread insoluble monolayers of polycaprolactone with various molecular weights was studied by measuring the decrease in surface area and in surface potential, in a barostat surface balance. The interfacial hydrolysis under the action of enzymes leads to the progressive fragmentation of the polymer molecules and to the appearance at the interface of charged insoluble and small soluble products. The solubilization of the small soluble fragments was detected by measuring the decrease in surface area during hydrolysis. An independent study showed that, in contrast to poly(lactic-co-glycolic acid) (PLAGA) oligomers, this solubilization is not instantaneous. Taking into account the solubilization rates, one can determine the kinetics of enzymatic hydrolysis. The specific catalytic activity of HLL was estimated in the framework of the random-scission model and compared to those obtained for the hydrolysis of monolayers built up of PLAGA or of simple di- and triglyceride molecules. Received: 25 July 2000 Revised: 28 November 2000 Accepted: 29 November 2000