title: Enzymatic Hydrolysis of Polyester Thin Films: Real-Time Analysis of Film Mass Changes and Dissipation Dynamics.
abstract: Cleavage of ester bonds by extracellular microbial hydrolases is considered a key step during the breakdown of biodegradable polyester materials in natural and engineered systems. Here we present a novel analytical approach for simultaneous detection of changes in the masses and rigidities of polyester thin films during enzymatic hydrolysis using a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D). In experiments with poly(butylene succinate) (PBS) and the lipase of Rhizopus oryzae (RoL), we detected complete hydrolysis of PBS thin films at pH 5 and 40 °C that proceeded through soft and water-rich film intermediates. Increasing the temperature from 20 to 40 °C resulted in a larger increase of the enzymatic hydrolysis rate of PBS than of nonpolymeric dibutyl adipate. This finding was ascribed to elevated accessibility of ester bonds to the catalytic site of RoL due to increasing polyester chain mobility. When the pH of the solution was changed from 5 to 7, initial hydrolysis rates were little affected, while a softer film intermediate that lead to incomplete film hydrolysis was formed. Hydrolysis dynamics of PBS, poly(butylene adipate), poly(lactic acid), and poly(ethylene terephthalate) in assays with RoL showed distinct differences that we attribute to differences in the polyester structure.
authors.affiliation: Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, Swiss Federal Institute of Technology (ETH) Zurich , 8092 Zurich, Switzerland.
authors.forename: Michael Thomas
authors.initials: MT
authors.lastname: Zumstein
authors.affiliation: Environmental Biochemistry Group, Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (EAWAG) , 8600 Dübendorf, Switzerland.
authors.forename: Hans-Peter E
authors.initials: HP
authors.lastname: Kohler
authors.affiliation: Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, Swiss Federal Institute of Technology (ETH) Zurich , 8092 Zurich, Switzerland.
authors.forename: Kristopher
authors.initials: K
authors.lastname: McNeill
authors.affiliation: Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, Swiss Federal Institute of Technology (ETH) Zurich , 8092 Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Sander
mesh_terms: D019149:Bioreactors; D005656:Fungal Proteins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008049:Lipase / Q000378:metabolism*; D011091:Polyesters / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D058525:Quartz Crystal Microbalance Techniques
chemical_list: D005656:Fungal Proteins; D011091:Polyesters; D008049:Lipase