The potential of cold-adapted microorganisms for biodegradation of bioplastics

Due to the extensive use of plastics, their quantity in the environment is constantly increasing, which creates a global problem. In the present study, we sought to isolate, test and identify Antarctic microorganisms which possess the ability to biodegrade bioplastics such as poly(ε-caprolactone) (PCL), poly(butylene succinate) (PBS) and poly(butylene succinate-co-butylene adipate) (PBSA) at low temperatures. 161 bacterial and 38 fungal isolates were isolated from 22 Antarctic soil samples. Among them, 92.16% of bacterial and 77.27% of fungal isolates formed a clear zone on emulsified PBSA, 98.04% and 81.82% on PBS and 100% and 77.27% on PCL as an additive to minimal medium at 20 °C. Based on the 16S and 18S rRNA sequences, bacterial strains were identified as species belonging to Pseudomonas and Bacillus and fungal strains as species belonging to Geomyces, Sclerotinia, Fusarium and Mortierella, while the yeast strain was identified as Hansenula anomala. In the biodegradation process conducted under laboratory conditions at 14, 20 and 28 °C, Sclerotinia sp. B11IV and Fusarium sp. B3'M strains showed the highest biodegradation activity at 20 °C (49.68% for PBSA and 33.7% for PCL, 45.99% for PBSA and 49.65% for PCL, respectively). The highest biodegradation rate for Geomyces sp. B10I was noted at 14 °C (25.67% for PBSA and 5.71% for PCL), which suggested a preference for lower temperatures (at 20 °C the biodegradation rate was only 11.34% for PBSA, and 4.46% for PCL). These data showed that microorganisms isolated from Antarctic regions are good candidates for effective plastic degradation at low temperatures.