Fate of Eight Different Polymers under Uncontrolled Composting Conditions: Relationships Between Deterioration, Biofilm Formation, and the Material Surface Properties

Abstract

With the ever-increasing volume of polymer wastes and their associated detrimental impacts on the environment, the plastic life cycle has drawn increasing attention. Here, eight commercial polymers selected from biodegradable to environmentally persistent materials, all formulated under a credit card format, were incubated in an outdoor compost to evaluate their fate over time and to profile the microbial communities colonizing their surfaces. After 450 days in compost, the samples were all colonized by multispecies biofilms, these latest displaying different amounts of adhered microbial biomass and significantly distinct bacterial and fungal community compositions depending on the substrate. Interestingly, colonization experiments on the eight polymers revealed a large core of shared microbial taxa, predominantly composed of microorganisms previously reported from environments contaminated with petroleum hydrocarbons or plastics debris. These observations suggest that biofilms may contribute to the alteration process of all the polymers studied. Actually, four substrates, independently of their assignment to a polymer group, displayed a significant deterioration, which might be attributed to biologically mediated mechanisms. Relevantly, the deterioration appears strongly associated with the formation of a high-cell density biofilm onto the polymer surfaces. The analysis of various surface properties revealed that roughness and hydrophilicity are likely prominent parameters for driving the biological interactions with the polymers.

Molecular Characterization of the Bacterial Community in Biofilms for Degradation of Poly(3-Hydroxybutyrate-<i>co</i>-3-Hydroxyhexanoate) Films in Seawater

“…General biodegradable plastics have mainly been evaluated for their biodegradability in soil environments. In a previous study, the degradation and biofilm formation of eight different plastics were evaluated under uncontrolled composting conditions ( 18 ). Two out of five polyesters, PBS and PHA, showed low, but significant weight loss after a 450-d incubation in compost.…”

Microplastics provide new microbial niches in aquatic environments

“…The roughness and hydrophobicity of microplastics constitute the most prominent parameters controlling microplastic surface properties and hence can greatly influence microbial community structure (Gong et al 2019 ; Mercier et al 2017 ). Aged-microplastics, produced via exposure to UV light or incubation in water for several weeks, usually have increased surface area, roughness and polarity compared to virgin samples (Brennecke et al 2016 ; Jemec Kokalj et al 2019 ; Liu et al 2019 ; Liu et al 2020 ).…”

A comparative study of degradation mechanisms of PHBV and PBSA under laboratory-scale composting conditions

“…PHBV and PBSA polyesters have very good biodegradability performances in various environments compared to other biodegradable polymers [6][7][8]. Poly(3-hydroxybutyrate) is actually considered as a suitable alternative for cellulose as a reference material in the standards of biodegradation for soil and water environments, respectively NF EN 17033 and ISO DIS 14852.…”

“…The results of Yang et al [8] have shown that PBSA and PCL biodegraded better than other polymers (PP, PLLA, PBS) in the same compost but the performance and mechanisms of biodegradation were not further investigated. The study of Mercier [7] compared the degradation of different polymers (EVOH, PP, PBAT, PET, PBS, scl-PHA, PLLA, PA66) in an uncontrolled compost simulating home composting conditions (average temperature of 13°C) and found that PBS and scl-PHA were the polymers which degraded the most with a mass loss of 5.5 and 8%, respectively after 450 days of incubation.…”