Microbial Degradation of Plastic in Aqueous Solutions Demonstrated by CO2 Evolution and Quantification

The environmental accumulation of plastics worldwide is a consequence of the durability of the material. Alternative polymers, marketed as biodegradable, present a potential solution to mitigate their ecological damage. However, understanding of biodegradability has been hindered by a lack of reproducible testing methods. We developed a novel method to evaluate the biodegradability of plastic samples based on the monitoring of bacterial respiration in aqueous media via the quantification of CO₂ produced, where the only carbon source available is from the polymer. <i>Rhodococcus rhodochrous</i> and <i>Alcanivorax borkumensis</i> were used as model organisms for soil and marine systems, respectively. Our results demonstrate that this approach is reproducible and can be used with a variety of plastics, allowing comparison of the relative biodegradability of the different materials. In the case of low-density polyethylene, the study demonstrated a clear correlation between the molecular weight of the sample and CO₂ released, taken as a measure of biodegradability.