Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 56, Issue 24, Pages 17732-17742Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.2c06583
Keywords
polyhydroxyalkanoate (PHA); additive; plasticizer; soil biodegradation; degradation mechanism; microbial analysis
Categories
Funding
- Australian Research Council [DP200101144]
- ARC Training Centre for Bioplastics and Biocomposites [IC210100023]
- Australian Research Council [IC210100023, DP200101144] Funding Source: Australian Research Council
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This study investigated the impact of the commonly used plasticizer DBP on the biodegradation of PHBV in soil. The presence of DBP delayed the initial stage of PHBV biodegradation but then accelerated subsequent rates of biodegradation. Furthermore, it led to significant increases in total bacterial and fungal biomass and altered the composition of microbial communities.
While new biodegradable materials are being rapidly introduced to address plastic pollution, their end-of-life impacts remain unclear. Biodegradable plastics typically comprise a biopolymer matrix with functional additives and/or solid fillers, which may be toxic. Here, using an established method for continuous biodegradation monitoring, we investigated the impact of a commonly used plasticizer, dibutyl phthalate (DBP), on the biodegradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) in soil. The presence of DBP delayed the initial stage of PHBV biodegradation but then accelerated subsequent rates of biodegradation. Furthermore, it led to significant increases in total bacterial and fungal biomass and altered the composition of microbial communities with significant increases in the relative abundances of Thauera (gammaproteobacterial) and Mucor circinelloides (fungal) populations. It is proposed, with evidence from biodegradation behavior and microbial analysis, that the presence of DBP likely stimulated a microbial community shift, introduced higher proportions of more readily degradable amorphous regions from the plasticizing effect, and facilitated access to the bulk polymer matrix for microorganisms or at least their associated enzymes. These effects in combination overcame the initial inhibition effect of the DBP and resulted in a net increase in the rate of biodegradation of PHBV.
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