Discovery of a Novel Bacillus sp. JO01 for the Degradation of Poly(butylene adipate- co -terephthalate)( PBAT) and Its Inhibition by PBAT Monomers

Abstract

Poly(butylene adipate-co-terephthalate) (PBAT) is a type of biodegradable plastic composed of both aliphatic and aromatic hydrocarbon polymers, which grants it the advantages of processability and flexibility along with increased interest. Studies have suggested that PBAT biodegradation mechanisms involve enzymatic breakdown by lipases. Our initial efforts in this study were therefore focused on identifying a novel PBAT-degrading bacterial strain with high degradation activity. Nine bacterial strains from various sources were screened and assessed for their ability to degrade PBAT. Bacillus sp. JO01 strain, exhibiting high similarity (99%) with Bacillus toyonensis BCT-7112, demonstrated superior PBAT degradation activity under various temperature conditions from 25 to 42°C. Timedependent PBAT degradation by Bacillus sp. JO01 indicated a maximum yield at 30°C, reaching 66% of film degradation measured. Besides PBAT, the strain showed degradability on PCL, PHB, and PBS. Physical characterization of the degraded PBAT films via scanning electron microscopy revealed that surface alterations such as cracks were reduced, as was the molecular weight. Bacillus sp. JO01 did not consume PBAT monomers, such as adipic acid (AA), 1,4-butanediol, and terephthalic acid (TPA). However, AA and TPA showed inhibitory effects on the degradation of PBAT films by Bacillus sp. JO01, resulting in 30% inhibition of degradation at 16 mM of AA and at 32 mM of TPA. This study highlights Bacillus sp. JO01 as a superior strain for PBAT degradation and suggests that PBAT monomers have an inhibitory effect on the degrading strains, which is an important consideration for the bulk degradation of bioplastics.