Degradation of biodegradable plastics by phytopathogenic smut fungi

We evaluated biodegradable plastic (BP) degradation abilities of various smut fungi (Ustilaginomycotina), including 8 isolates from 6 species of Ustilaginales, 3 isolates from 2 species of Exobasidiales, 7 isolates from 5 species of Tilletiales, and 3 isolates from 3 species of Microbotryales belonging to the anther smut fungi (Pucciniomycotina). The BP-degrading abilities of these fungal isolates were compared to that of a known BP-degrader, Moesziomyces antarcticus JCM 10317. The BPs tested were polycaprolactone (PCL), polybutylene succinate adipate (PBSA), polybutylene succinate (PBS), and polylactic acid (PLA). BP-degrading ability was quantified by measuring the clear zones produced by fungi on BP-containing media at temperatures from 10 ℃ to 30 ℃. The experiments revealed 10 isolates from 7 species capable of degrading PBSA and PCL, and 7 isolates from 4 species capable of degrading PBS. No isolates degraded the PLA. Notably, the PBSA-degrading ability of one isolate of Ustilago trichophora was significantly higher than that of JCM 10317 at low temperature. However, JCM 10317 was superior at degrading PCL and PBS. Our results indicate that smut fungi are potentially valuable sources of isolates with superior BP-degrading ability.