New Biodegradable Plastic Breaks Down in Deep Ocean Testing

A new type of biodegradable plastic, known as poly(d-lactate-co-3-hydroxybutyrate) or LAHB, has demonstrated significant potential for breaking down in the deep ocean environment, according to researchers from Shinshu University in Japan. Unlike conventional plastics, which can last for decades in marine ecosystems, LAHB has shown a remarkable ability to degrade, losing more than 80% of its mass after just 13 months when submerged nearly 855 meters below the ocean surface.

The study, led by Professor Seiichi Taguchi and his team, revealed that LAHB is effectively broken down by deep-sea microbes. These microorganisms utilize specialized enzymes to decompose the plastic into harmless byproducts such as carbon dioxide and water. In stark contrast, traditional polylactide (PLA) plastic remained completely intact during the same period, highlighting the advantages of LAHB in addressing plastic pollution.

Research Insights on Biodegradation

The research team conducted real-world underwater testing near Hatsushima Island, where they submerged two types of LAHB films—one containing approximately 6% lactic acid (P6LAHB) and another with 13% lactic acid (P13LAHB)—alongside a conventional PLA film. The deep-sea conditions included cold temperatures of around 3.6 °C, high salinity, and low dissolved oxygen levels, which typically hinder microbial activity.

After seven months, the P13LAHB film exhibited a weight loss of 30.9%, and after 13 months, it had lost more than 82% of its mass. The P6LAHB film showed similar trends, while the PLA film showed no measurable degradation. This research underscores the potential of LAHB as a viable solution to combat the alarming issue of plastic waste in the oceans.

The findings indicate that LAHB films developed visible cracks and were colonized by biofilms comprising various microbes, which are essential for the degradation process. The PLA film, conversely, remained devoid of any microbial activity.

Understanding the Microbial Mechanisms

To further comprehend how LAHB decomposes, researchers analyzed the microbial community, termed the plastisphere, that formed on the plastic’s surface. The study identified several dominant genera, including Colwellia and Pseudoteredinibacter, which produce enzymes that break down long polymer chains into smaller fragments.

These fragments are further processed by other microbes that consume the resulting monomers. The collaborative effort of these microbial communities ultimately transforms the plastic into harmless compounds that reintegrate into the marine ecosystem.

The research findings have been published in the journal Polymer Degradation and Stability, in a paper titled “Unveiling deep-sea biodegradation of microbially produced lactate-based polyester (LAHB) via plastisphere metagenomics and metatranscriptomics.” This significant advancement in biodegradable materials offers a promising avenue for reducing plastic pollution in our oceans, where traditional plastics pose a substantial threat to marine life and ecosystems.

By harnessing the natural processes of deep-sea microbes, scientists aim to contribute to a more sustainable future and address one of the most pressing environmental challenges of our time.