Biocatalyzed approach for the surface functionalization of poly(L‐lactic acid) films using hydrolytic enzymes

Abstract

Poly(lactic acid) as a biodegradable thermoplastic polyester has received increasing attention. This renewable polyester has found applications in a wide range of products such as food packaging, textiles and biomedical devices. Its major drawbacks are poor toughness, slow degradation rate and lack of reactive side-chain groups. An enzymatic process for the grafting of carboxylic acids onto the surface of poly(L-lactic acid) (PLLA) films was developed using Candida antarctica lipase B as a catalyst. Enzymatic hydrolysis of the PLLA film using Humicola insolens cutinase in order to increase the number of hydroxyl and carboxylic groups on the outer polymer chains for grafting was also assessed and showed a change of water contact angle from 74.6 to 33.1° while the roughness and waviness were an order of magnitude higher in comparison to the blank. Surface functionalization was demonstrated using two different techniques, (14) C-radiochemical analysis and X-ray photoelectron spectroscopy (XPS) using (14) C-butyric acid sodium salt and 4,4,4-trifluorobutyric acid as model molecules, respectively. XPS analysis showed that 4,4,4-trifluorobutyric acid was enzymatically coupled based on an increase of the fluor content from 0.19 to 0.40%. The presented (14) C-radiochemical analyses are consistent with the XPS data indicating the potential of enzymatic functionalization in different reaction conditions.

Nature Inspired Solutions for Polymers: Will Cutinase Enzymes Make Polyesters and Polyamides Greener?

“…Hydrolytic activities on PBS were reported also for cutinases from Fusarium solani, from Aspergillus oryzae, from Alternaria brassicicola, and from Humicola insolens [74]. The latter was also reported to be active in the hydrolysis of poly(lactic acid) as well as cutinases from Thermobifida halotolerans [70,77]. Finally, cutinase from Fusarium solani is currently reported as the only cutinase able to hydrolyze Polyamide 6,6 [80].…”

“…On the other hand, the ability of enzymes to hydrolyze polymers can be exploited for structural fine-tuning and for controlling the degree of polymer functionalization by operating under mild conditions [57]. The possibility to perform partial hydrolysis on the outer layer of the polymer can be exploited for changing the superficial properties in terms of hydrophobicity/hydrophilicity balance, obtaining reactive groups for successive modifications, and changing the polymer biocompatibility just to name a few [68][69][70].…”

Enzymatic Degradation of Aromatic and Aliphatic Polyesters by P. pastoris Expressed Cutinase 1 from Thermobifida cellulosilytica

“…In case of PBS films, pieces of 0.5 × 1.0 cm were cut and washed in three serial steps (5 g/L Triton X-100, 100 mM Na 2 CO 3 , and ddH 2 O; each for 30 min at 50°C and 100 rpm) prior to hydrolysis reactions in order to remove possible surface contaminations (Pellis et al, 2015, in press; Gamerith et al, 2016). Incubations were performed in 2 mL tubes at 100 rpm and 65°C for different time frames.…”

“…HPLC-RI detection of released products from PHBV and PBS was performed as previously reported by Pellis et al (2015). Briefly, hydrolysis samples were precipitated following the Carrez method and filtered through 0.45 μm Nylon filters (GVS, Indianapolis, USA).…”

“…Various enzymes belonging to the cutinase family were reported to hydrolyze PET, the most used polyester (Yoon et al, 2002; Vertommen et al, 2005; Herzog et al, 2006; Heumann et al, 2006; Donelli et al, 2009; Herrero Acero et al, 2011; Ribitsch et al, 2011, 2012; Kanelli et al, 2015). Moreover, reports on the biocatalyzed hydrolysis of poly(lactic acid) (Pellis et al, 2015, in press; Ortner et al, 2017), poly(butylene succinate) (Hu et al, 2016) and poly(ethylene furanoate) (Pellis et al, 2016b) using similar biocatalysts were also described and certify the importance of such processes in the optics of a sustainable development (Clark et al, 2016; Pellis et al, 2016c). Despite the high industrial potential reported for cutinases from Thermobifida spp., these enzymes have usually been obtained by intracellular recombinant expression in E. coli (Herrero Acero et al, 2011; Su et al, 2013; Roth et al, 2014; Then et al, 2016), an approach that hampers the scale-up of the production process.…”