Transcriptomic profiling under poly (L-lactide) polymer degradation of the thermophilic filamentous bacterium Laceyella sacchari LP175 and its potential for polymer film hydrolysis

Polylactide or polylactic acid (PLA) is a hydrolysable polymer used in many applications including medical devices, agricultural films, and packaging materials. Biological methods that completely decompose biodegradable polymers are environmentally beneficial. Laceyella sacchari LP175, a thermophilic filamentous bacterium, had a high potential producing poly (L-lactide) (PLLA)-degrading enzyme which is characterized as a serine protease. This study demonstrated that this strain is an effective degrader of PLLA at a high temperature of 50 °C, which resulted in an increase in enzyme activity within the initial 24 h of incubation. The alterations in the physical and structural characteristics of the PLLA polymer film were verified to occur when incubated with a culture supernatant of this strain. Transcriptomic profiling revealed the differentially expressed genes of Laceyella sacchari LP175 under PLLA degradation, showing 289 and 296 up-regulated and down-regulated genes, respectively. Findings indicated that serine protease and transport-related genes played a key role in the biodegradation of PLLA in Laceyella sacchari LP175. The functions and metabolic pathway annotation of the enriched expression genes showed that propanoate metabolism, protein secretion, and membrane transportation were the main pathways induced when cells were grown in the presence of PLLA powder. Therefore, transcriptome data will be helpful in the development and manipulation of microbial systems to improve the degradation of biodegradable polymers.