# Impact of Plasticizers on the Microbial Degradation of Polyhydroxybutyrate (PHB)

## TL;DR

This study shows that adding plasticizers to PHB does not hinder its biodegradation by bacteria, making it a viable eco-friendly plastic alternative.

## Contribution

The study demonstrates that plasticizers do not interfere with PHB biodegradation or microbial activity.

## Key findings

- PHB degradation exceeded 98% within 48 hours in liquid medium with no significant differences from the control.
- Soil experiments showed plasticized PHB films degraded up to 80% within 10 weeks, similar to additive-free films.
- Plasticizers did not affect bacterial viability or the expression of the PHB depolymerase gene.

## Abstract

Polyhydroxybutyrate (PHB) is a biodegradable polyester considered a sustainable alternative to petroleum-based plastics. However, its biodegradation in the presence of plasticizers remains poorly defined. This study investigated the impact of phthalate ester- and glycol-based plasticizers on PHB degradation by Ralstonia sp. C1. Real Time -Polymerase Chain Reaction(RT-PCR) analysis showed that expression of the PHB depolymerase gene phaZa1 remained unchanged in all additive-treated cultures, indicating no transcriptional interference. Liquid-medium degradation assays quantified by HPLC revealed rapid PHB utilization, with more than 50% degraded within 24 h and over 98% degraded within 48 h, with no significant differences relative to the control. Growth-inhibition assays further demonstrated that none of the plasticizers impaired bacterial viability, as OD600 profiles were comparable to untreated cultures. Soil degradation experiments confirmed that PHB films containing additives decomposed at rates similar to additive-free films, reaching approximately 80% degradation within 10 weeks. Overall, the tested plasticizers did not affect enzyme expression, microbial activity, or PHB biodegradation, highlighting the suitability of plasticized PHB materials for environmentally sustainable applications and supporting their scalable use as biodegradable alternatives to conventional plastics.