MICROBIAL-DEGRADATION OF POLY-(L-LACTIC ACID) OLIGOMERS

Biotic and abiotic degradation of poly-(L-lactic acid) (PLLA) oligomer s of molecular weight (MW) 260-2880 g mol(-1) has been studied in an a quatic aerobic headspace biodegradation test for six months. Water sol uble/dispersable PLLA oligomers (MW 260-550 g mol(-1)) biodegraded at 25 degrees C and at 58 degrees C. Larger, crystalline and hydrophobic oligomers (MW 550-2880 g mol(-1)) biodegraded only at 58 degrees C. We ight-average molecular weights of PLLA-oligomers decreased both during biotic and abiotic degradation, although slightly more during biotic degradation. The surface and inner structures of biotically incubated PLLA oligomers were more porous than those of abiotically degraded oli gomers. Thus abiotic hydrolysis of PLLA-structure to lactic acid appea rs to be an essential, but not the only explanation for its degradatio n. PLLA polymer chain seems to be cleaved also enzymatically to lactic acid. (C) 1998 Elsevier Science Limited. All rights reserved.