Biodegradation of Polylactide Modified with Starch by Selected Species of Molds

Abstract

-The new technology of polylactide (PLA) production using starch as an additive compound was developed in order to reduce costs of the process. Two different PLA samples were obtained: with 20% and 50% starch concentrations. The comparative analysis of modified and unmodified PLA biodegradation is presented. PLA film with different content of starch was cut to small square-shaped pieces. The samples were disinfected, weighed under sterile conditions and placed on the agar plate with mineral medium. Samples on the agar plate were treated with two species of molds, i.e. Aspergillus niger and Penicillium minioluteum. The cultures were grown for 91 days at 21°C. Subsequently, the samples were analyzed by weight loss. The modification of foil samples chemical structure was analysed by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR). To study the effect of microorganisms on structure of the tested PLA samples Scanning Electron Microscope (SEM) was applied. The greatest weight loss (about 20%) was observed for the PLA film containing 50% of starch while the weight loss for the PLA with 20% of starch was two times lower. FTIR technique in the analyzed range showed visible changes of PLA spectrum treated with A. niger and P. minioluteum.The changes of signal intensity indicating the reorganization of bonds in tested range of the spectra were observed. The SEM photographs of molds treated samples also demonstrated changes of the PLA film structure which was visibly rough in comparison to smooth surface of the control samples. Chemical and physical changes in the structure of the both species molds treated PLA samples were the clearer, the higher were starch content in PLA.