Respirometric measurement of the stereochemical effects on the biodegradation of polylactic and polyglutamic acid in a simulated compost environment

The need for better disposal methods for plastics and plastic products has led to increased, testing of new biodegradable polymers for their ability to degrade in a laboratory compost system. Such testing aids in the development of commercial plastic products intended to degrade under normal landfill conditions without posing environmental problems. Mixtures of 90% D/10% L and 50% D/50% L Polyglutamic acid have shown that the stereochemistry of the polymer subunit plays an important role in its degradation; showing an 8.3% and 41.3% mineraliztion respectively over a 10 day period. Testing of a second set of similar samples of PGA also showed high rates of degradation, and may be a result of stereochemical effects. Testing of Polylactic acid mixtures resulted in a 3.9 and 4.9% mineralization for the 100% D isomer after 10 and 15 days, respectively and 0% mineralization for the L isomer after an eight day period. Testing of these two polymers shows that stereochemistry is important in the degradation of polymers in a simulated compost environment, and needs to be considered when developing commercial polymer products that are intended to biodegrade.