POLYMER DEGRADATION AND STABILITY
Mario Ivan Penas; Miryam Criado-Gonzalez; Antxon Martínez de Ilarduya; Araceli Flores; Jean-Marie Raquez; Rosica Mincheva; Alejandro J. Müller; Rebeca Hernandez.
Biodegradation of polyesters driven by enzymes is considered as one of the most effective way of degradation of these materials, as a way to control plastics accumulation in the environment. In this study, we present two different strategies to tune the enzymatic degradation of PBS films triggered by a lipase from Pseudomonas cepacia. Firstly, the kinetics of enzymatic degradation of PBS films was regulated by applying multilayer coats of polysaccharide alginate and chitosan (Alg/Chi) films. Secondly, self-degradable PBS films were prepared by embedding lipase-filled alginate particles. For comparison purposes, a detailed enzymatic degradation study of neat PBS films exposed to a lipase from P. cepacia in solution was made to determine the main experimental parameters influencing their degradation in solution. The results showed that an increase in enzyme concentration increased the degradation extent and rate of neat PBS films. At a fixed enzyme concentration, stirring of the solution containing the enzyme and the PBS also increased the biodegradation rate. In the case of the PBS films coated with a different number of Alg/Chi layers by spray-assisted LbL and subjected to enzymatic degradation experiments in solution, the extent of degradation was found to be dependent on the number of protective coating layers. Therefore, the Alg/Chi biobased coating constitutes an effective barrier to the diffusion of the lipase, thus proving its effectiveness in modulating the enzymatic activity as a function of coating thickness. In the case of self-degradable PBS containing lipase-embedded alginate beads (employed to protect the enzyme during high-temperature processing), only limited biodegradation was observed as the amount of encapsulated enzyme employed was too small. Nonetheless, these results are promising, as the enzymatic activity –indicative of the degradation capacity of the enzyme– determined for all these samples was about 2 orders of magnitude lower than that of previous assays.
Link to source: https://addi.ehu.es/bitstream/handle/10810/61574/1-s2.0-S0141391023000939-main.pdf?sequence=1
A2.4. Preparation and characterization of polyelectrolyte multilayer spraycoated PBS films
Spray-assisted layer-by-layer deposition was employed for the coating of PBS films with polysaccharide aqueous solutions following a procedure reported elsewhere [31,42]. First, PBS films were cut into 25 × 10 mm2 and introduced individually into a polyethylenimine (PEI) solution (1 mg/mL) for 5 minutes to confer PBS a more hydrophilic surface, as well as providing a positively charged surface, for a better deposition of the polysaccharide coating [31–33,43]. After that, the films were air-dried and washed for 2 minutes with Milli-Q water. Then, they were placed onto a metallic support for the multilayer spray-coating in the automatic equipment (ND-SP Spray Coater, Nadetech Innovations, Spain).