Both lipase PS and Novozym 435 promote the ring-opening polymerization of lacOCA, the O-carboxylic anhydride derived from lactic acid. Accordingly, PLA of relatively high molecular weights (M-n up to 38400 g/mol) and low polydispersities (M-w/M-n < 1.4) are obtained in high yields within a few hours at 80 degrees C. Slight preference for L-lacOCA over D-lacOCA is observed, and with Novozym 435, the molecular weight of the obtained PLA can be controlled by varying the lipase loading.