Comprehensive strategies for microcystin degradation: A review of the physical, chemical, and biological methods and genetic engineering.

Addressing the threat of harmful cyanobacterial blooms (CyanoHABs) and their associated microcystins (MCs) is crucial for global drinking water safety. In this review, we comprehensively analyze and compares the physical, chemical, and biological methods and genetic engineering for MCs degradation in aquatic environments. Physical methods, such as UV treatments and photocatalytic reactions, have a high efficiency in breaking down MCs, with the potential for further enhancement in performance and reduction of hazardous byproducts. Chemical treatments using chlorine dioxide and potassium permanganate can reduce MC levels but require careful dosage management to avoid toxic by-products and protect aquatic ecosystems. Biological methods, including microbial degradation and phytoremediation techniques, show promise for the biodegradation of MCs, offering reduced environmental impact and increased sustainability. Genetic engineering, such as immobilization of microcystinase A (MlrA) in Escherichia coli and its expression in Synechocystis sp., has proven effective in decomposing MCs such as MC-LR. However, challenges related to specific environmental conditions such as temperature variations, pH levels, presence of other contaminants, nutrient availability, oxygen levels, and light exposure, as well as scalability of biological systems, necessitate further exploration. We provide a comprehensive evaluation of MCs degradation techniques, delving into their practicality, assessing the environmental impacts, and scrutinizing their efficiency to offer crucial insights into the multifaceted nature of these methods in various environmental contexts. The integration of various methodologies to enhance degradation efficiency is vital in the field of water safety, underscoring the need for ongoing innovation.

Comparative toxicological analysis of two pristine carbon nanomaterials (graphene oxide and aminated graphene oxide) and their corresponding degraded forms using human in vitro models.

Despite the wide application of graphene-based materials, the information of the toxicity associated to some specific derivatives such as aminated graphene oxide is scarce. Likewise, most of these studies analyse the pristine materials, while the available data regarding the harmful effects of degraded forms is very limited. In this work, the toxicity of graphene oxide (GO), aminated graphene oxide (GO-NH2), and their respective degraded forms (dGO and dGO-NH2) obtained after being submitted to high-intensity sonication was evaluated applying in vitro assays in different models of human exposure. Viability and ROS assays were performed on A549 and HT29 cells, while their skin irritation potential was tested on a reconstructed human epidermis model. The obtained results showed that GO-NH2 and dGO-NH2 substantially decrease cell viability in the lung and gastrointestinal models, being this reduction slightly higher in the cells exposed to the degraded forms. In contrast, this parameter was not affected by GO and dGO which, conversely, showed the ability to induce higher levels of ROS than the pristine and degraded aminated forms. Furthermore, none of the materials is skin irritant. Altogether, these results provide new insights about the potential harmful effects of the selected graphene-based nanomaterials in comparison with their degraded counterparts.

Physical soil attributes in areas under forest/pasture conversion in northern Rondônia, Brazil.

The main cause of physical degradation in pasture areas is overgrazing, and when combined with poorly productive soils, it causes the loss of millions of hectares of agricultural soils a year. Thus, work is needed to indicate which physical attributes are most sensitive to degradation, generating information so that soil management can be proposed, with a view to economic, social, and environmental aspects. Therefore, the objective of the work was to evaluate the impacts caused on the physical attributes of the soil, in forests converted to pastures in northern Rondônia, Brazil. The study was carried out in three areas within the municipality of Porto Velho, Rondônia, one area with forest and two with pastures (brachiaria and mombaça grass). In the field, deformed soil samples were collected at a depth of 0.00-0.10 and 0.10-0.20 m in the three study areas. In the laboratory, physical analyses of texture, aggregates and porosity, compaction, and an additional analysis of soil organic carbon were carried out. Then, univariate, bivariate, and multivariate analyses were performed, as well as geostatistical analysis. The conversion of forest to pasture had a negative impact on aggregates, compaction, porosity, and accumulation of organic carbon in the soil. The studied environments are influenced by the high levels of sand and clay, which interfere in the aggregation, compaction, porosity, and accumulation of organic carbon in the soil. We observed greater spatial variability of physical attributes in the environment with mombaça grass and attributed this to the greater grazing and trampling intensity of the animals.