Characterization and Identification of Lipolytic Bacteria Forming Polystyrene (PS) Plastic Biofilm Based on 16S rRNA Genes

Plastic waste, especially polystyrene (PS), has become a global environmental problem. Previous studies have collected biofilm-forming lipolytic bacteria in PS plastic degradation experiments but have not been characterized. This study aims to characterize and identify biofilm-forming lipolytic bacteria on PS plastic surfaces through phenotypic and molecular approaches based on the 16S rRNA gene. A total of 12 bacterial isolates were reconfirmed for their lipolytic potential on tributyrin agar (TBA) media. Furthermore, isolates with lipolytic index (IL) > 2 were characterized based on colony morphology and molecular identification based on 16S rRNA gene. The results showed that there were 5 isolates with IL > 2, namely IL A-7, IL MK-5, IL S-6, IL S-3, and IL S-2. Morphologically, the five isolates are bone white with round colony shape. Gram staining results are purple (Gram positive). Molecular identification showed that IL MK-5, IL S-6, and IL S-2 were related to Priestia megaterium with 100% similarity, while IL A-7 and IL S-3 were related to Bacillus methylotrophicus and Bacillus tequilensis with 99.93% similarity, respectively. It can be concluded that the biofilm-forming lipolytic bacteria on PS plastic are the genera Bacillus and Priestia. The results of this study provide new insights into the potential of lipolytic bacteria in plastic biodegradation, especially PS plastic.