Degradation of poly (lactic acid) and nanocomposites by Bacillus licheniformis.
OBJECTIVE
The disposal problem due to non-degradable petroleum-based plastics has raised the demand for biodegradable polymers. The degradation of poly (lactic acid) (PLA) has been studied for several years, but the understanding of involved mechanisms is still incomplete. Based on our previous studies, and it is hypothesized an enzymatic involvement, the aim of this study was to continue investigations on the degradation of PLA and its nanocomposites by Bacillus licheniformis.


METHODS
Biodegradation of PLA and its nanocomposites (CLOISITE 30B and SOMASIF MEE) was performed on compression-molded, 25 × 25 × 0.6-mm films. Firstly, two plastic films were dipped into sterile nutrient broth inoculated with B. licheniformis and incubated at 32°C. Then, to verify if biodegradation was due to extracellular esterase, the culture broth was filtered to remove B. licheniformis cells, and the plastic materials were put into this broth.


CONCLUSIONS
PLA degradation by B. licheniformis was accelerated by the presence of organoclays. After 5 months in liquid culture, nanocomposites showed only the 10% of residual mass, compared with the 60% of pure PLA. Extracellular esterase activity was detected in the filtered culture broth confirming that PLA biodegradation was probably due to this enzyme action.
Dipartimento di Scienze Agronomiche, Agrochimiche e delle Produzioni animali, Sezione di Scienze Agrochimiche, Università di Catania, Via S. Sofia 98, 95123 Catania, Italy.
Maria
M
Arena
Cristina
C
Abbate
Kikku
K
Fukushima
Mara
M
Gennari
D001407:Bacillus / Q000201:enzymology* / Q000254:growth & development*; D001673:Biodegradation, Environmental; D004950:Esterases / Q000032:analysis; D019344:Lactic Acid / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites / Q000737:chemistry*; D011091:Polyesters; D011108:Polymers / Q000378:metabolism*
D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide); D004950:Esterases
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