Evaluation of the Biodegradation Efficiency of Four Various Types of Plastics by Pseudomonas aeruginosa Isolated from the Gut Extract of Superworms

Abstract

Plastic waste worldwide is becoming a serious pollution problem for the planet. Various physical and chemical methods have been tested in attempts to remove plastic dumps. However, these have usually resulted in secondary pollution issues. Recently, the biodegradation of plastic by fungal and bacterial strains has been spotlighted as a promising solution to remove plastic wastes without generating secondary pollution. We have previously reported that a Pseudomonas aeruginosa strain isolated from the gut of a superworm is capable of biodegrading polystyrene (PS) and polyphenylene sulfide (PPS). Herein, we demonstrate the extraordinary biodegradative power of P. aeruginosa in efficiently depolymerizing four different types of plastics: PS, PPS, polyethylene (PE) and polypropylene (PP). We further compared biodegradation rates for these four plastic types and found that PE was biodegraded fastest, whereas the biodegradation of PP was the slowest. Moreover, the growth rates of P. aeruginosa were not always proportional to biodegradation rates, suggesting that the rate of bacterial growth could be influenced by the composition and properties of intermediate molecules produced during plastic biodegradation, and these may supply useful cellular precursors and energy. In conclusion, an initial screening system to select the most suitable bacterial strain to biodegrade certain types of plastic is particularly important and may be necessary to solve plastic waste problems both presently and in the future.

Biodegradation of Different Types of Plastics by Tenebrio molitor Insect

“…Surface alterations of the plastics are characteristic of the aging processes occurring under the influence of microorganisms (present in the intestines of insects) or, more specifically, enzymes secreted by them. The folding of the previously smooth surface of the polymer and the formation of pitting was observed during the biodegradation of PS and PE with the bacterium P. aeruginosa isolated from the gut of Zophobas morio insect (Tenebrionidae; cousin of mealworm, known also as superworm) [52]. Surface elements mapping comparison of PS and PE before and after biodegradation showed that those changes were connected with increase in oxygen content, which suggests oxidative changes in the plastics [52].…”

“…The folding of the previously smooth surface of the polymer and the formation of pitting was observed during the biodegradation of PS and PE with the bacterium P. aeruginosa isolated from the gut of Zophobas morio insect (Tenebrionidae; cousin of mealworm, known also as superworm) [52]. Surface elements mapping comparison of PS and PE before and after biodegradation showed that those changes were connected with increase in oxygen content, which suggests oxidative changes in the plastics [52]. Similar changes as observed by us in the case of PU foams had been observed by [53] after biodegradation trials in soil burial.…”

Progressing Plastics Circularity: A Review of Mechano-Biocatalytic Approaches for Waste Plastic (Re)valorization

“…On the other hand, a mealworm managed to mineralize 49% of LDPE foam after a month ( Brandon et al, 2018 ). Gut microbiome seems to change with PE-diet and some of the abundant strains have been isolated and tested against the polymer by themselves, however biodegradation proceeds in a much slower rate and extent ( Yang et al, 2014 ; Brandon et al, 2018 ; Lee et al, 2020 ).…”

Worming the Circular Economy for Biowaste and Plastics: Hermetia illucens, Tenebrio Molitor and Zophobas morio

“…Interstingly, their value comes in dealing with plastic waste, particularly polystyrene (PS) and polyethylene(PE). It is their ability of consuming and mineralizing PS & PE [16,35] that would be the focus of their contribution to the circular economy of plastic waste.…”