Transcriptomic analysis of PLA-degrading bacteria Brevibacillus brevis grown on polylactic acid

Polylactic acid (PLA) is a promising biodegradable material used in various fields, such as mulching films and disposable packaging materials. Biological approaches for completely degrading biodegradable polymers can provide environmentally friendly solutions. However, to our knowledge, no studies have performed transcriptome profiling to analyze PLA-degrading genes of PLA-degrading bacteria. Therefore, this study reports for the first time an RNA sequence approach for tracing genes involved in PLA biodegradation in the PLA-degrading bacterium Brevibacillus brevis. As a result, the hydrolase genes (mhqD, nap, and besA) were mainly up-regulated, indicating that the hydrolase plays a key role in the biodegradation of PLA by B. brevis. In addition, genes involved in biofilm formation and transporter genes were also up-regulated. Taken together, genes related to biofilm formation were up-regulated for access to PLA and biodegradation, and hydrolase genes were upregulated to degrade PLA into lactic acid oligomers and monomers. Finally, transport-related genes were upregulated for cellular assimilation of the degraded oligomers. Our results provide transcriptome-based insights into the biodegradation mechanism of PLA, which pitches a better understanding of microbial biodegradation of plastics.