Selection of a Pseudonocardia sp. RM423 that accelerates the biodegradation of poly(lactic) acid in submerged cultures and in soil microcosms

The biodegradability of poly(lactic) acid (PLA) by the actinomycete Pseudonocardia sp. RM423 was studied under submerged conditions. Film-weight loss was 15.0% after 4 weeks of cultivation. Amendment of basal salt medium (BSM) broth with 0.3% (w/v) gelatin as an enzyme inducer increased PLA biodegradation by Pseudonocardia sp. RM423 to 70.9%. The biodegradation of PLA in soil bioaugmented with Pseudonocardia sp. RM423 was evaluated by measuring the carbon dioxide produced from a vessel containing mixtures of PLA sheets and enriched soil incubated at mesophilic and thermophilic conditions. At 58 ± 2 °C, the PLA biodegradation in the soil with Pseudonocardia sp. RM423 was higher than that in uninoculated soil. PLA sheets in bacterially inoculated soil under thermophilic conditions were obviously disintegrated and had the highest percentages of PLA biodegradation and PLA-weight loss. Our findings indicate that soil bioaugmentation with Pseudonocardia sp. RM423 can accelerate PLA biodegradation in the soil under both mesophilic and thermophilic conditions.