Biodegradation of Polystyrene by Pseudomonas sp. Isolated from the Gut of Superworms (Larvae of Zophobas atratus).

Recently, various attempts have been made to solve plastic waste problems, such as development of biodegradation without producing pollution. Polystyrene (PS) is the fifth most used plastic in many industries; therefore, degrading PS becomes a critical global issue. Here, we reported Pseudomonas aeruginosa strain DSM 50071, initially isolated from the gut of the superworms, Zophobas atratus, and the PS degradation by Pseudomonas sp. DSM 50071. We examined PS degradation using electronic microscopy and measured changes in atomic composition and contact angles with water droplets on the PS surface that represents a chemical change from hydrophobicity to hydrophilicity. We have further examined chemical structural changes using X-ray photoelectron spectroscopy, Fourier-transform-infrared spectroscopy, and nuclear magnetic resonance (NMR) to confirm the formation of carbonyl groups (C═O) in the oxidation pathway during PS biodegradation. In reverse transcription quantitative polymerase chain reaction analysis, the gene expression level of serine hydrolase (SH) in Pseudomonas sp. DSM 50071 was highly increased during PS degradation, and the enzyme-mediated biodegradation of PS was further confirmed by the SH inhibitor treatment test. Thus, the significance of these findings goes beyond the discovery of a novel function of Pseudomonas sp. DSM 50071 in the gut of superworms, highlighting a potential solution for PS biodegradation.

Rapid biodegradation of polyphenylene sulfide plastic beads by Pseudomonas sp.

Pseudomonas sp. isolated from soil, are bioremediating microorganisms that are capable of degrading various types of plastics. Polyphenylene sulfide (PPS) has the most excellent structural stability among general plastics and thus is extremely difficult to break down using physical or chemical methods. This study demonstrates the efficient biodegradation of PPS by Pseudomonas sp., which exists in the gut of superworms. Compared with the conventional film-type of plastic, the degradation efficiencies to the bead form of plastic were significantly improved and thus the biodegradation time was dramatically shortened. Therefore, instead of film-type plastics, we used 300 µm diameter plastic beads for the measurement of Pseudomonas sp.-mediated biodegradation of PPS during a 10-day period. This method not only can be used for comparison and verification of the biodegradation efficiency of different types of plastics within a short reaction time of 10 days, but also provides the possibility to develop a new and more efficient screening system to rapidly identify the most efficient species of bacteria for the biodegradation of various types of plastics.