Biodegradable plastics represent one approach to reducing the proliferation of plastic waste on the deep-sea floor. Approximately 1.14 million tons of biodegradable plastics were produced in 202213<\/a><\/sup>. Their biodegradability has been investigated using International Organization for Standardization testing methods in aerobic and anaerobic conditions in compost, soil, and river water14<\/a>,15<\/a><\/sup>. In the case of marine biodegradation, a Biochemical Oxygen Demand (BOD) biodegradation test using seawater15<\/a>,16<\/a><\/sup> and a field test at the shore17<\/a>,18<\/a><\/sup> are performed. However, little is known about the capacity of deep-sea bacterial communities that live in extreme environmental conditions of temperature and pressure to decompose the most common forms of biodegradable plastic debris on an ecological time scale. In addition, it is not fully understood whether the biodegradable plastics that have been developed currently degrade in this extreme environment, the deep-sea floor, in the same way, that they degrade on shore, or how long it takes for them to degrade.<\/p>\n\n\n\n We addressed this deficit by conducting short- and long-term biodegradation tests at five deep-sea floor locations in Pacific Ocean: three bathyal sites [off Misaki Port (BMS, depth\u2009=\u2009757\u2009m), off Hatsushima Island (BHT, depth\u2009=\u2009855\u2009m), and Myojin Knoll (BMJ, depth\u2009=\u20091292\u2009m)], and two abyssal sites [Kuroshio Extension Observatory (AKR, depth\u2009=\u20095503\u2009m) and Minamitorishima Island (AMN, depth\u2009=\u20095552\u2009m)] (Fig. 1a, b<\/a> and Table 1<\/a>). At the same time, a control experiment was conducted at the port of JAMSTEC Yokosuka Headquarters (PJM, depth\u2009=\u20092\u20136\u2009m). Table 1<\/a> shows the sites where the samples were placed, latitude\/longitude information, depth below sea level, salinity, temperature, dissolved oxygen, date of placement, date of recovery, and an abbreviation describing the site and duration of the placement. All of the samples used in this study (formal names, abbreviations, thermal properties, and chemical structures) are summarized in Table 2<\/a> and Supplementary Fig. 1<\/a>.<\/p>\n\n\n Table 1 Summary of the on-site degradation test site<\/strong><\/p>\n\n\n\n Full size table<\/a>Table 2 Formal name, abbreviation in the paper, and thermal properties of samples<\/strong><\/p>\n\n\n\n Full size table<\/a><\/p>\n\n\n\n Biodegradable plastic-degrading microorganisms have been isolated from compost, soil, rivers, and seawater19<\/a>,20<\/a><\/sup>. Degrading enzymes that they secrete have been isolated and purified21<\/a><\/sup>, and biochemical properties, amino acid sequences, and three-dimensional crystal structures of these enzymes have been reported22<\/a><\/sup>. However, only a few polyhydroxyalkanoate (PHA)-degrading microorganisms have been reported on the deep-sea floor23<\/a><\/sup>, and no microorganisms capable of degrading other biodegradable plastics are known in that environment, raising questions about deep-sea degradation mechanisms. Therefore, investigating the decomposition of biodegradable plastics on the deep-sea floor will significantly contribute to the development of knowledge and technologies in the fields of materials science and biology, in addition to environmental conservation and understanding of the deep-sea environment. In this study, the decomposition of biodegradable plastics in the deep-sea was investigated for biodegradable polyesters and polysaccharide ester derivatives, in addition to PHA, which has been actively studied: we assessed weight loss, reduction in material thickness, and surface morphological changes at the deep-sea floor, biofilm formation, microbial accumulation, and candidate genes for degradation of plastics by growing microbes.<\/p>\n\n\n\n We investigated the decomposition of representative biodegradable plastics (PHA, biodegradable polyesters, and polysaccharide esters) at the above-described five deep-sea floor locations (Fig. 1a, b<\/a>). Injection-molded samples and films were placed in custom-made sample holders and mesh bags, respectively, and were placed on the deep-sea floor in a condition that prevented physical deformation [samples were placed in polyethylene terephthalate (PET) containers with holes, protected by tennis nets (Fig. 1<\/a>c, d, Supplementary Figs. 2<\/a>, 3<\/a>)]. Installation in the deep-sea and recovery of the samples were performed aboard the Shinkai 6500<\/em> human-occupied vehicle (HOV) using a robotic arm. The seafloor soil immediately below the samples was also recovered using a custom-made core and used for microbiological analysis (Fig. 1<\/a>e\u2013g, Supplementary Fig. 4<\/a>).<\/p>\n\n\n\n Figure 2a\u2013c<\/a> shows the overall shapes and morphology of poly[(R<\/em>)\u22123-hydroxybutyrate-co<\/em>-(R<\/em>)\u22123-hydroxyhexanoate] (PHBH) injection-molded samples placed on shore (PJM12) and off Hatsushima Island (BHT14) and Minamitorishima Island (AMN13) for approximately 1 year. The PHBH sample shown as an example is one in which degradation had progressed relatively well compared with other samples. The photographs taken from the top and the end after ultrasonic washing and drying, revealed that no physical deformation had occurred. Furthermore, it was confirmed by X-ray diffraction that the crystal structure of samples remained unchanged during the submersion periods at the deep-sea floor and experimental processing. Scanning electron microscopy (SEM) images (Fig. 2d<\/a>) show the surface profiles after removal of microorganisms from the surface. Whereas the surface morphology before degradation (original) was very smooth, the surfaces of the samples after placement on the shore or the deep-sea floor were observed to be uneven, and degradation was in progress. This kind of degradation that creates unevenness on the surface of the material is considered to be due to microbial degradation, not physical deformation or chemical degradation. The fact that degradation progresses from the surface homogeneously is evident from the extreme decrease in the thickness of the samples from the shore (PJM12). In about 1 year, the thickness of the samples, which was initially 4000\u2009\u03bcm, was found to have decreased by ~700\u2009\u03bcm at the shore (PJM12), ~110\u2009\u03bcm off Hatsushima Island (BHT14), and ~10\u2009\u03bcm at Minamitorishima Island (AMN13). On the basis of this series of observations, the degradation was considered to be microbial degradation, rather than physical deformation.<\/p>\n\n\n <\/p>\n\n\n\n You may read the full article at https:\/\/www.nature.com\/articles\/s41467-023-44<\/a><\/strong>368-8<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" Abstract Microbes can decompose biodegradable plastics on land, rivers and seashore. However, it is unclear whether deep-sea microbes can degrade biodegradable plastics in the extreme environmental conditions of the seafloor. Here, we report microbial decomposition of representative biodegradable plastics (polyhydroxyalkanoates, biodegradable polyesters, and polysaccharide esters) at diverse deep-sea floor locations ranging in depth from 757 […]<\/p>\n","protected":false},"author":59,"featured_media":138558,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"none","nova_meta_subtitle":"Several dominant microorganisms are carrying genes potentially encoding plastic-degrading enzymes such as polyhydroxyalkanoate depolymerases and cutinases\/polyesterases","footnotes":""},"categories":[5572],"tags":[11270,5838,5847,5840,12615],"supplier":[23508,23506,8063,168,23507,2202],"class_list":["post-138541","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-bio-based","tag-biodegradability","tag-bioeconomy","tag-bioplastics","tag-enzymes","tag-microbes","supplier-gunma-university-center-for-food-science-and-wellness-gucfw","supplier-japan-agency-for-marine-earth-science-and-technology-jamstec","supplier-japan-bioplastics-association","supplier-national-institute-of-advanced-industrial-science-and-technology-aist","supplier-national-institute-of-technology-and-evaluation-nbrc","supplier-university-of-tokyo"],"_links":{"self":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/138541","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/users\/59"}],"replies":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/comments?post=138541"}],"version-history":[{"count":0,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/138541\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/media\/138558"}],"wp:attachment":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/media?parent=138541"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/categories?post=138541"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/tags?post=138541"},{"taxonomy":"supplier","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/supplier?post=138541"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"figure](\"https:\/\/media.springernature.com\/lw685\/springer-static\/image\/art%3A10.1038%2Fs41467-023-44368-8\/MediaObjects\/41467_2023_44368_Fig1_HTML.png\")
<\/a>Results and discussion<\/h3>\n\n\n\n
Biodegradation at the deep-sea floor<\/h3>\n\n\n\n
Biodegradation of biodegradable polyesters at the deep-sea floor<\/h3>\n\n\n\n
![\"Fig.](\"https:\/\/media.springernature.com\/lw685\/springer-static\/image\/art%3A10.1038%2Fs41467-023-44368-8\/MediaObjects\/41467_2023_44368_Fig2_HTML.png\")
<\/a>