Effect of different size microplastic particles on the construction of algal-bacterial biofilms and microbial communities.

Algal-bacterial symbiotic system is a biological purification system that combines sewage treatment with resource utilization and has the dual effects of carbon sequestration and pollution reduction. In this study, an immobilized algal-bacterial biofilm system was constructed for the treatment of natural sewage. Effects of exposure to microplastics (MPs) with different particle diameters (0.065 µm, 0.5 µm and 5 µm) were determined in terms of algal biomass recovery efficiency, the composition of extracellular polymeric substances (EPS) and morphologic characteristics. The impacts of MPs on the bacterial diversity and community structure of biofilms were also examined. The metagenomic analysis of key microorganisms and related metabolism pathways involved in system was further investigated. Results showed that following exposure to 5 µm MP, a maximum algal recovery efficiency of 80% was achieved, with a minimum PSII primary light energy conversion efficiency (Fv/Fm ratio) of 0.513. Furthermore, 5 µm MP caused the highest level of damage to the algal-bacterial biofilm, enhancing the secretion of protein-rich EPS. The biofilm morphology became rough and loose following exposure to 0.5 µm and 5 µm MP. Community diversity and richness were significantly high in biofilms exposed to 5 µm MP. Proteobacteria (15.3-24.1%), Firmicutes (5.0-7.8%) and Actinobacteria (4.2-4.9%) were dominant in all groups, with exposure to 5 µm MP resulting in the highest relative abundance for these species. The addition of MPs promoted the related metabolic functions while inhibited the degradation of harmful substances by algal-bacterial biofilms. The findings have environmental significance for the practical application of algal-bacterial biofilms for sewage treatment, providing novel insights into the potential effects of MPs on immobilized algal-bacterial biofilm systems.

Altered gut microbiome composition by appendectomy contributes to colorectal cancer.

Appendectomy impacts the homeostasis of gut microbiome in patients. We aimed to study the role of appendectomy in colorectal cancer (CRC) risk through causing gut microbial dysbiosis. Population-based longitudinal study (cohort 1, n = 129,155) showed a 73.0% increase in CRC risk among appendectomy cases throughout 20 years follow-up (Adjusted sub-distribution hazard ratio (SHR) 1.73, 95% CI 1.49-2.01, P < 0.001). Shotgun metagenomic sequencing was performed on fecal samples from cohort 2 (n = 314). Gut microbial dysbiosis in appendectomy subjects was observed with significant enrichment of 7 CRC-promoting bacteria (Bacteroides vulgatus, Bacteroides fragilis, Veillonella dispar, Prevotella ruminicola, Prevotella fucsa, Prevotella dentalis, Prevotella denticola) and depletion of 5 beneficial commensals (Blautia sp YL58, Enterococcus hirae, Lachnospiraceae bacterium Choco86, Collinsella aerofaciens, Blautia sp SC05B48). Microbial network analysis showed increased correlation strengths among enriched bacteria and their enriched oncogenic pathways in appendectomy subjects compared to controls. Of which, B. fragilis was the centrality in the network of the enriched bacteria. We further confirmed that appendectomy promoted colorectal tumorigenesis in mice by causing gut microbial dysbiosis and impaired intestinal barrier function. Collectively, this study revealed appendectomy-induced microbial dysbiosis characterized by enriched CRC-promoting bacteria and depleted beneficial commensals, signifying that the gut microbiome may play a crucial role in CRC development induced by appendectomy.

New approach to recycle office waste paper: Reinforcement for polyurethane with nano cellulose crystals extracted from waste paper.

New approach to recycle office waste paper was purposed in this paper, i.e., cellulose nanocrystal (CNC) was extracted from waste paper and then used CNC as the organic filler to reinforce polyurethane elastomer (PUE) in thermal properties. A series of CNC/PUE nanocomposites was prepared in situ using a two-step process in solvent N,N-dimethylformamide solution by changing the content of CNC from 0.5, 1, 2, 3, 4 to 5 wt%. The results showed that CNC was covalently bonded to PUE, and specifically concerned with the hard segments of PUE resulting from the strong hydrogen bonding. The interactions between CNC and PUE caused the increased thermal and thermo-mechanical properties, and decreased water absorption of nanocomposites. Importantly, the initial degradation temperature of PUE with 2 wt% content CNC (CNC/PUE2) increased by 21 °C. CNC/PUE2 had the better comprehensive properties with the worse water absorption, which made CNC/PUE2 appealing in load bearing and outdoor applications. Hence, this work not only provided a new recycling method of waste paper but also provided a thermolstable PUE with lower cost.

Structure and thermal properties of various alcoholysis products from waste poly(ethylene terephthalate).

Waste polyethylene terephthalate (PET) has been a core member in plastic polluters due to the great amount consumption in food packaging, soft-drink bottles, fibers and films. It is essential to recycle waste PET and alcoholysis is a significant way to accomplish chemical recycling. In this work, three kinds of dihydric alcohols, including neopentyl glycol (NPG), dipropylene glycol (DPG) and poly(propylene glycol) (PPG), were employed to decompose waste PET with different temperatures, catalysts, and PET. A series of alcoholysis products with different appearance were obtained. The bulk structure and thermal properties of alcoholysis products were investigated by FTIR, 1H NMR, MALDI-TOF, DSC and TG experiments. It is found that poly(propylene glycol) may react with waste PET to generate copolymer instead of oligomer products, dimers or trimers, etc. This product possesses excellent shelf stability and present transparent appearance, which may hold a great potential application in chemical industry. Moreover, the alcoholysis activity of DPG is the lowest comparing with NPG and EG in degradation of waste PET.