Biodegradation and Anti-Bacterial Properties of PLA and Wood/PLA Composites Incorporated with Zeomic Anti-Bacterial Agent

Abstract

Anti-bacterial and biodegradation activities of Poly (lactic acid) (PLA) and wood flour/PLA composites (WPLA) were investigated for the effect of anti-bacterial agent addition. Silver substituted Zeolite (commercially designated as Zeomic) was used as anti-bacterial agent in this study. Anti-bacterial activities were investigated through dynamic shake flask method accompanying with plate count agar (PCA) technique, against Staphylococcus aureus as testing bacteria. The results of anti-bacterial activity were reported by viable cell count. For biodegradation test, the degree and rate of biodegradations were evaluated from percentage of carbon conversion, the test being carried out under laboratory controlled-aerobic degradation environment at a temperature of 58±2°C. The results found that addition of Zeomic did not perform anti-bacterial activities for both the neat PLA and WPLA due to non-diffusivity of silver in Zeomic. For biodegradation test, both PLA and WPLA samples during incubation times of 21-60 days had shown considerable biodegradation rates as a result of chain scission by hydrolysis reaction and subsequent enzymatic-biodegradation by microorganism of PLA molecules. Regarding the effect of wood and Zeomic addition, it was found that introducing wood and Zeomic in PLA matrix tended to markedly increase the degree and rate of biodegradation of PLA and WPLA materials, whereby the PLA having 10%wt of wood with 1.5%wt of Zeomic had the most satisfactory biodegradation level and rate as a consequence of accelerated hydrolysis degradation from moisture in wood and Zeomic.