Influence of microbial biomass content on biodegradation and mechanical properties of poly(3-hydroxybutyrate) composites.

Biodegradation rates and mechanical properties of poly(3-hydroxybutyrate) (PHB) composites with green algae and cyanobacteria were investigated for the first time. To the authors knowledge, the addition of microbial biomass led to the biggest observed effect on biodegradation so far. The composites with microbial biomass showed an acceleration of the biodegradation rate and a higher cumulative biodegradation within 132 days compared to PHB or the biomass alone. In order to determine the causes for the faster biodegradation, the molecular weight, the crystallinity, the water uptake, the microbial biomass composition and scanning electron microscope images were assessed. The molecular weight of the PHB in the composites was lower than that of pure PHB while the crystallinity and microbial biomass composition were the same for all samples. A direct correlation of water uptake and crystallinity with biodegradation rate could not be observed. While the degradation of molecular weight of PHB during sample preparation contributed to the improvement of biodegradation, the main reason was attributed to biostimulation by the added biomass. The resulting enhancement of the biodegradation rate appears to be unique in the field of polymer biodegradation. The tensile strength was lowered, elongation at break remained constant and Young's modulus was increased compared to pure PHB.

Classification and Regression Machine Learning Models for Predicting Aerobic Ready and Inherent Biodegradation of Organic Chemicals in Water.

Machine learning (ML) is viewed as a promising tool for the prediction of aerobic biodegradation, one of the most important elimination pathways of organic chemicals from the environment. However, available models only have small datasets (<3200 records), make binary classification predictions, evaluate ready biodegradability, and do not incorporate experimental conditions (e.g., system setup and reaction time). This study addressed all these limitations by first compiling a large database of 12,750 records, considering both ready and inherent biodegradation under different conditions, and then developing regression and classification models using different chemical representations and ML algorithms. The best regression model (R2 = 0.54 and root mean square error of 0.25) and classification model (the prediction accuracy from 85.1%) achieved very good performance. The model interpretation indicated that the models correctly captured the effects of chemical substructures, following the order of C═O > O═C-O > OH > CH3 > halogen > branching > N > 6-member ring. The consideration of chemical speciation based on pKa and α notations did not affect the regression model performance but significantly improved the classification model performance (the accuracy increased to 87.6%). The models also showed large applicability domains and provided reasonable predictions for more than 98% of over 850,000 environmentally relevant chemicals in the Distributed Structure-Searchable Toxicity database. These robust, trustable models were finally made widely accessible through two free online predictors with graphical user interface.

Correlating Catalyst Design and Discharged Product to Reduce Overpotential in Li-CO2 Batteries.

Li-CO2 batteries with dual efficacy for greenhouse gas CO2 sequestration and high energy output have been regarded as a promising electrochemical energy storage technology. However, battery feasibility has been hampered by inferior electrochemical performance due to large overpotentials and low cyclability primarily caused by the difficult decomposition of ultra-stable Li2 CO3 during charge. The use of cathode catalysts has been highlighted as a promising solution and catalyst properties, as well as the nature of discharge products, are closely correlated with electrochemical performance. Here, the catalyst design strategies that include active site enrichment, electrical transport enhancement, and mass transfer improvement are summarized. Catalyst effects on product decomposition are then subsequently introduced, while product geometry and chemical composition will be explored, with an emphasis on the formation/decomposition of Li2 C2 O4 instead of Li2 CO3 . Building on previous research, future directions that facilitate improvements in catalyst design are put forward to reinforce the fundamental development of Li-CO2 batteries.

Long-Term Photostability in Terephthalate Metal-Organic Frameworks.

Prolonged (weeks) UV/Vis irradiation under Ar of UiO-66(Zr), UiO66 Zr-NO2 , MIL101 Fe, MIL125 Ti-NH2 , MIL101 Cr and MIL101 Cr(Pt) shows that these MOFs undergo photodecarboxylation of benzenedicarboxylate (BDC) linker in a significant percentage depending on the structure and composition of the material. Routine characterization techniques such as XRD, UV/Vis spectroscopy and TGA fail to detect changes in the material, although porosity and surface area change upon irradiation of powders. In contrast to BCD-containing MOFs, zeolitic imidazolate ZIF-8 does not evolve CO2 or any other gas upon irradiation.

Dose-dependent reactions of Aporrectodea caliginosa to perfluorooctanoic acid and perfluorooctanesulfonic acid in soil.

As a consequence of their widespread use, e.g. as protective coatings for fabrics, and their resistance to thermal and biological breakdown, perfluorinated compounds are increasingly found in the environment, but little is known about their ecotoxicological properties. A 40-day microcosm experiment was carried out to examine the effects of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) on the endogeic geophagus earthworm Aporrectodea caliginosa, its survival and feeding on soil organic C and microbial biomass C. Three levels of concentration (1, 100, and 500 mg kg(-1)) were chosen. The lowest represented the maximum found in sediments and soils and the other two are extreme concentrations that might occur in pollution hotspots and that have been shown to poison organisms. Earthworms promoted the production of CO2 and decreased microbial biomass C in soil, regardless of the presence of PFOA or PFOS. Both compounds significantly decreased the surviving numbers and dry weight of earthworms at concentrations of 100 mg kg(-1). No earthworms survived at PFOA and PFOS concentrations of 500 mg kg(-1). At concentrations of 1 mg kg(-1), no negative effects were observed. The δ(13)C values of A. caliginosa did not differ between treatments. In contrast, the δ(15)N values were significantly increased after adding 1 mg kg(-1) of PFOA, reflecting elevated portions of soil-derived N in the earthworm tissue. In contrast, these portions of soil-derived N were lower in the earthworms after addition of 100 mg kg(-1) of PFOA and PFOS. In conclusion, extreme concentrations of PFOA and PFOS negatively affected endogeic A. caliginosa, whereas a concentration of 1 mg kg(-1) of PFOA and PFOS was related to an increased uptake of soil N by the earthworms.

Diuron, hexazinone, and sulfometuron-methyl applied alone and in mixture in soils: Distribution of extractable residue, bound residue, biodegradation, and mineralization.

Biodegradation studies of herbicides applied to the soil alone and in a mixture are required since herbicides are often used in combinations to control weeds. When herbicides are applied in mixtures, interactions may affect their environmental fate. Thus, the objective of this study was to evaluate the distribution of extractable residue, bound residue, biodegradation, and mineralization of diuron, hexazinone, and sulfometuron-methyl when applied alone and in a mixture in two agricultural soils. Biometric flasks filled with two types of soil (clay and sandy) collected from an area cultivated with sugarcane and treated with 14C-radiolabeled solutions of the herbicides were incubated for 70 d. More 14C-CO2 was released when sulfometuron-methyl and hexazinone were applied in a mixture compared to when applied alone. Being used in a combination did not affect the mineralization of diuron. The soil texture directly influenced the mineralization, bound residue, and extractable residue of the three herbicides. The percentage of extractable residue decreased over time for all herbicides. Hexazinone and sulfometuron-methyl had the highest residue extracted on sandy soil when applied alone. Diuron showed the highest percentage of bound residue. The degradation of the three herbicides was higher in the clay soil regardless of the mode of application, which is related to the higher potential of the bacterial community in the clay soil to mineralize the herbicides.

Exploitation of bacterial strains for microplastics (LDPE) biodegradation.

Plastic waste (microplastics) is one of the primary sources of environmental pollutants, serving as a reservoir for them. In this study, previously isolated and screened polymer-degrading bacteria (B. subtilis V8, P. aminophilusB1 4-, P. putida C 2 5, P. aeruginosa V1, and A. calcoaceticus V4) were utilised to examine the biodegradation of LDPE (low-density polyethylene) microplastics. Response surface methodology (RSM) was used to optimize the physicochemical growth parameters (pH, temperature, and ammonium sulphate concentration). By using the polyphasic approach, including CO2 estimation, weight loss analysis, scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, and electrical conductivities examine the plastic biodegradability. After four months, all biodegradable plastic samples were evaluated. When compared to the other tested cultures, P. aeruginosa V1 showed the most significant degradation (CO2evolution of 8.86 g.l-l and percentage weight loss of 18.21 %) with increased electrical conductivity, followed by B. subtilis V8 (CO2 evolution of 8.10 g.l-l and percentage weight loss of 16.12 %), A. calcoaceticus V4 (CO2 evolution of 7.21 g.l-l and percentage weight loss of 15.44 %), P. putida C 2-5 (CO2 evolution of 5.76 g.l-l and percentage weight loss of 13.30 %), and P. aminophilus B1 4- (CO2 evolution of 5.62 g.l-l and percentage weight loss of 11.72 %). The deteriorated materials' exterior modifications (surface alteration) were also examined using SEM analysis, and the chemical bonding alterations (bond vibration-bending) were determined using FT-IR spectroscopy.

Biomassa e atividade microbiana do solo em sistemas de produção olerícola orgânica e convencional / Biomass and soil microbial activity on horticulture organic and conventional crop systems

O cultivo de olerícolas pode ser produzido no sistema convencional utilizando defensivos agrícolas e fertilizantes sintéticos, ou no sistema orgânico, quando não há a utilização de defensivos sintéticos e tem como principal fonte de adubação, resíduos orgânicos. Este trabalho teve como objetivo avaliar a biomassa e a atividade microbiana do solo em sistemas de cultivo orgânico e convencional com suas respectivas áreas de referência. Para isso, foram coletadas amostras de solo em três propriedades agrícolas com sistema de cultivo convencional e outras três com sistema de cultivo orgânico, além de suas respectivas áreas de referência. Foram determinados o carbono e nitrogênio microbiano e total, e a respiração basal após 57 dias de incubação. A maior variação na taxa de respiração basal entre a área de produção e a área de referência foi observada no sistema orgânico. Os teores de nutrientes no solo, carbono e nitrogênio microbianos foram maiores nas áreas de produção do que os encontrados nas áreas de referência.

The horticultural crops can be produced with the conventional system using pesticides and synthetic fertilizers, or organic system where there is no use of synthetic pesticides and its main source of nutrients are organic wastes. This study aimed to assess the biomass and soil microbial activity in organic production systems and conventional with their respective reference areas. In this study, soil samples were sampled in three farms with conventional tillage and three other with organ system, and their respective reference areas. It was determined total carbon and nitrogen and microbial, and microbial activity after 57 days of incubation. The greatest variation in basal respiration rate between the respective production area and reference area was observed in the organic system. The nutrients in the soil microbial carbon and nitrogen were higher in the production areas than those in the reference areas.