Isolation and characterization of bacteria capable of degrading poly(lactic acid) at ambient temperature

Four bacteria, Chryseobacterium sp., Sphingobacterium sp. and two strains of Pseudomonas aeruginosa, capable of degrading poly(lactic acid), PLA, at mesophillic temperatures (∼30 °C) were isolated. Their growth and formation of biofilm on PLA was characterized. To establish the biodegradation role of these bacteria and to assess any possible influence of abiotic factors in the biodegradation of PLA at 30 °C, the biodegradation rate of each strain was measured as the reduction of weight average molecular number (Mn) of PLA. A rapid reduction of PLA Mn was observed when incubated with each strain. Abiotic controls showed very slow degradation rates. Only the P. aeruginosa isolates were able to grow on lactate suggesting that there is a novel mechanism for degradation by Chryseobacterium sp. and Sphingobacterium sp. All four strains were capable of forming biofilm on the surface of PLA films consistent with the observed polymer degradation. This comparative study establishes the role of these isolates in the degradation of PLA at ambient temperature with minimal assistance from abiotic factors.