4:05 PM - 4:25 PM
[BBG01-08] Biodegradation process of biogenic and chemosynthetic plastics in marine environment
★Invited Papers
Keywords:biodegradable plastic, metagenome, metatranscriptomics, biodegradation
Life on Earth has evolved a wide variety of metabolic functions to adapt to the drastically changing environment since emergence of life. As a result, microorganisms are now able to inhabit all kinds of biospheres with different physical and chemical constraints, from the Earth's surface to the stratosphere and the deep subsurface. With the development of human civilization, new materials that were almost non-existent on the Earth have been created and are now being released into the global environment. Microorganisms inhabiting the earth have continued to adapt and evolve to such substances, and it is believed that new metabolic functions are being created, evolved, and adapted even now.
Since the degradation of plastics in the marine environment is particularly difficult for microorganisms, development of biodegradable plastics in the ocean has been promoted in recent years. However, understanding of the plastic degraders in the ocean and enzymes that contribute to biodegradability is still poor. In this study, we investigated the oceanic degradability of poly(butylene succinate-co-adipate) (PBSA), a chemosynthetic biodegradable plastic, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a biogenic biodegradable plastic, by the immersion tests at the quay of JAMSTEC’s Yokosuka Headquarters. We performed scanning electron microscopic observations of biofilms formed on the plastics and multi-meta-omics analyses to identify the plastic-degrading microorganisms and the enzymes involved in the biodegradation process.
After the immersion tests for 2-4 months, both DNA and RNA were co-extracted from the biofilms on the PBSA and PHBV, and comprehensively sequenced to identify the plastic degraders and the expressed plastic-degrading genes. From the plastisphere metagenomes, many draft genomes (metagenome-assembled genome, MAG) were extracted. At the same time, gene expression profiles of the highly abundant MAGs were analyzed by mapping mRNA reads, which provided comprehensive view of the highly expressed genes in the plastisphere. From the results, the putative plastic-degrading genes such as esterases were found in both plastispheres; however, the scheme of the oceanic biodegradation was quite different between the chemosynthetic PBSA and the biogenic PHBV.
Consequently, we successfully identified the microbial lineages and functional genes of plastic-degrading microorganisms in natural oceanic environment by integrating the metagenomic and metatranscriptomic analyses. This knowledge will contribute to the future development of marine biodegradable plastics.
Since the degradation of plastics in the marine environment is particularly difficult for microorganisms, development of biodegradable plastics in the ocean has been promoted in recent years. However, understanding of the plastic degraders in the ocean and enzymes that contribute to biodegradability is still poor. In this study, we investigated the oceanic degradability of poly(butylene succinate-co-adipate) (PBSA), a chemosynthetic biodegradable plastic, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a biogenic biodegradable plastic, by the immersion tests at the quay of JAMSTEC’s Yokosuka Headquarters. We performed scanning electron microscopic observations of biofilms formed on the plastics and multi-meta-omics analyses to identify the plastic-degrading microorganisms and the enzymes involved in the biodegradation process.
After the immersion tests for 2-4 months, both DNA and RNA were co-extracted from the biofilms on the PBSA and PHBV, and comprehensively sequenced to identify the plastic degraders and the expressed plastic-degrading genes. From the plastisphere metagenomes, many draft genomes (metagenome-assembled genome, MAG) were extracted. At the same time, gene expression profiles of the highly abundant MAGs were analyzed by mapping mRNA reads, which provided comprehensive view of the highly expressed genes in the plastisphere. From the results, the putative plastic-degrading genes such as esterases were found in both plastispheres; however, the scheme of the oceanic biodegradation was quite different between the chemosynthetic PBSA and the biogenic PHBV.
Consequently, we successfully identified the microbial lineages and functional genes of plastic-degrading microorganisms in natural oceanic environment by integrating the metagenomic and metatranscriptomic analyses. This knowledge will contribute to the future development of marine biodegradable plastics.