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Study on the onset mechanism of bio-blister degradation of polyolefin by diatom attachment in seawater.

ABSTRACT: It is essential to develop a mechanism for lowering the molecular weight of polyolefins to achieve biodegradation in seawater. In this study, a polypropylene/polylactic acid blend sample was first subjected to photodegradation pretreatment, and it was confirmed that in pure water, the acid generated promotes the polypropylene degradation (autoxidation), while in alkaline seawater, the promotion was inhibited by a neutralization reaction. In the autoxidation of polyolefins in alkaline seawater, aqueous Cl^- was also the inhibitor. However, we found that autoxidation could be initiated even in seawater by lowering the pH and using dissociation of ClOH (called blister degradation). The blister degradation mechanism enabled autoxidation, even in seawater, by taking advantage of the ability of diatoms to secrete transparent exopolymer particles (TEP) to prevent direct contact between the surface layer of polyolefins and alkaline seawater. We named blister degradation in seawater with diatoms as bio-blister degradation and confirmed its manifestation using linear low-density polyethylene (LLDPE)/starch samples by SEM, IR, DSC and GPC analysis.

SUBMITTER: Nakatani H

PROVIDER: S-EPMC10873352 | biostudies-literature | 2024 Feb

REPOSITORIES: biostudies-literature

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Study on the onset mechanism of bio-blister degradation of polyolefin by diatom attachment in seawater.

Nakatani Hisayuki H Narizumi Shun S Okubo Seiya S Motokucho Suguru S Dao Anh Thi Ngoc ATN Kim Hee-Jin HJ Yagi Mitsuharu M Kyozuka Yusaku Y Miura Shigenobu S Josyula Kanth V KV

Scientific reports 20240216 1

It is essential to develop a mechanism for lowering the molecular weight of polyolefins to achieve biodegradation in seawater. In this study, a polypropylene/polylactic acid blend sample was first subjected to photodegradation pretreatment, and it was confirmed that in pure water, the acid generated promotes the polypropylene degradation (autoxidation), while in alkaline seawater, the promotion was inhibited by a neutralization reaction. In the autoxidation of polyolefins in alkaline seawater, a ...[more]

PMID: 38366080

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Project description:Peptides were identified during degradation of the diatom Thalassiosira weissflogii with and without the use of the enzyme trypsin. This allows comparison of protein degradation occurring within the experiment (no trypsin added; peptides already present due to in situ degradation) and the protein still available for future degradation (peptides released from protein when trypsin is added during analysis). Over the 12-day degradation experiment 31% of the particulate organic carbon was depleted and there was no preferential degradation of the overall protein pool. However, there was distinct differentiation in the cellular location, secondary structure and modifications of the peptides that were either degraded or remained. During the initial period of rapid algal decay and bacterial growth, intracellular components from the cytoplasm were selectively consumed, resulting in the accumulation of membrane-associated proteins and peptides in the detrital pool. Accompanying this was an increase in the importance of membrane-bound ɑ-helix motifs. At the end of the 12 day experiment, the natural bacterial assemblage was focusing on degradation of membrane-associated proteins, which was the dominant source of peptides in both the residual pool (released by trypsin) and the actively degraded pool (no trypsin added). Methylated arginine, a post-translationally modified amino acid that is produced within the diatom prior to senescence, is found in high amounts within the detrital peptide pool, suggesting a link between in-cell modification and resistance to immediate degradation. Another modification - asparagine deamidation - appears to occur during degradation and deamidated peptides also accumulate within the detritus. The bacterial community decomposing the algal material was rich in proteobacteria, and employed a growth approach focusing on accumulation of solubilized material across their membranes and on DNA replication. At this early stage of diagenesis, no changes in bulk amino acids (THAA) were observed, yet a peptidomic approach allowed us to observe the differential changes in diatom protein preservation by discriminating between intracellular location, secondary structure, and modifications status.

Project description:Viruses influence microbial community structure and biogeochemical cycles in marine environments. Viral attachment to nonhost surfaces could influence host viral infection rates; however, the prevalence of such viral attachment is not investigated quantitatively. We used coastal seawater viral assemblages and, as models, marine vibriophage (SIO-2) and enterobacteriophages (T2 and T4) to investigate their attachment to probable nonhost marine bacteria. We also studied viral attachment to colloids and other abiotic surfaces in seawater. Centrifugation experiments with bacterium-virus mixtures showed substantial viral loss in the supernatant presumably due to the viral attachment to bacteria. This attachment (0.04 to 24 viruses μm-2 [bacterial surface area]) varied with bacterium-virus combinations. Surprisingly, filtering seawater on 0.2-μm Anodisc or polycarbonate filters retained ∼12 to 84% of viruses presumably attached to ≥0.2-μm-sized particles and/or the filter surface. Enzymatic digestion followed by epifluorescence and atomic force microscopy suggested that 7 to 25% of the total viruses were attached via β-glycosidic linkages. Furthermore, a substantial proportion (7 to 48%) of viruses became attached to model abiotic surfaces (polycarbonate, polypropylene, and glass), and this has significance for laboratory protocols as well as studies of virus ecology in particle-rich marine environments. Substantial attachment of viruses to nonhost surfaces could influence virus-driven biogeochemical cycles and microbial community structure.IMPORTANCE Viruses play important roles in altering microbial community structure and biogeochemical cycles in marine environments. Viral attachment to nonhost surfaces can influence host viral infection rates; however, the prevalence of viral attachment to nonhost surfaces and the ratio of attached viruses to total viruses are little known. We used coastal seawater viral assemblages and used marine vibriophage (SIO-2) and enterobacteriophages (T2 and T4) as models to investigate their attachment to abiotic and biotic surfaces in seawater. Viral attachment was observed on several surfaces, such as nonhost bacteria, polymers, filters, cover glasses, and tube surfaces. This study cautions against commonly used protocols that require viral incubation and seawater fractionation. More importantly, these results could influence virus-driven biogeochemical cycles and microbial community structure in the ocean.

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Study on the onset mechanism of bio-blister degradation of polyolefin by diatom attachment in seawater.

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Study on the onset mechanism of bio-blister degradation of polyolefin by diatom attachment in seawater.

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