[P004] Poster

1:00 PM - 1:50 PM JST(4:00 AM - 4:50 AM UTC)

[P02-260] Biodegradation of Polyamide 6/66 by Marine Microbial Communities and Isolated Strains

○Yugo Miyakawa¹, Shota Ando^2,3, Hironori Taguchi⁴, Takako Kikuchi⁴, Yoko Furuno⁵, Risa Yokoyama⁵, Kaho Tsuchiya⁶, Munenori Hayashida⁶, Yusuke Saito⁶, Namiko Gibu⁷, Dai-ichiro Kato⁵, Miwa Yamada⁶, Kohzo Ito^2,3, Daisuke Kasai¹ (1. Nagaoka Univ. of Tech. (Japan), 2. The Univ. of Tokyo (Japan), 3. NIMS (Japan), 4. CERI (Japan), 5. Kagoshima Univ. (Japan), 6. Iwate Univ. (Japan), 7. NIT, Okinawa College (Japan))

Keywords:

Polyamide,Marine Biodegradation,16S rRNA Gene Sequencing

Polyamides (PAs), commonly known as nylons, are petroleum-based thermoplastics characterized by amide bond linkages that confer high mechanical strength and durability. Copolymers of polyamide 6 and 6,6 (PA6/66) are extensively used in fishing gear. While designed for harsh conditions, these properties contribute to their detrimental persistence in marine environments. Discarded "ghost gear" gradually fragments into microplastics, posing physical threats to marine organisms and acting as vectors for pollutants. Despite the recognition of PAs as significant marine pollutants, their environmental fate remains insufficiently understood. Compared to other polymers like polyethylene or polyethylene terephthalate, studies on biodegradation of high-molecular-weight PA6/66 are limited. Although recent reports suggest partial biodegradation of PA6/66 under natural marine conditions, the detailed mechanisms and the specific microorganisms involved remain largely unclear. This study aimed to identify marine microorganisms involved in the PA6/66 biodegradation.
First, we investigated the biodegradability of PA6/66 powders in extracted seawater by measuring biochemical oxygen demand (BOD). An increase in BOD was observed during incubation with the PA6/66 powders, strongly suggesting that biodegradation of PA6/66 had occurred. Furthermore, bacterial community structures were analyzed using 16S rRNA gene amplicon sequencing. The results revealed that specific bacterial taxa became highly dominant during the incubation, indicating their potential involvement in polymer degradation. To further isolate responsible microorganisms, enrichment cultures were established using seawater supplemented with PA6/66 powders. Following enrichment, microbial colonies were screened on agar media containing emulsified PA6/66. Several colonies induced the formation of clearing zones on the emulsified medium, demonstrating potential interactions between the microorganisms and the polymer material. These colonies were successfully selected as candidate strains potentially involved in PA6/66 biodegradation.
This study provides a crucial initial identification of microbial communities and isolates associated with PA6/66 biodegradation in marine environments. Although detailed chemical analyses are ongoing, the combined approach of BOD measurement, microbial community analysis, and enrichment-based screening successfully enabled the isolation of promising candidate strains. Future studies will focus on the functional characterization of these isolates, contributing to a deeper understanding of PA6/66 biodegradation mechanisms in marine ecosystems.
This work was partially supported by NEDO [Moonshot R&D–Millennia Program] Grant, grant number NEDO JPNP18016.