Laccase-assisted biosensing constructs – Robust modalities to detect and remove environmental contaminants

Extremozyme-Based Biosensors for Environmental Pollution Monitoring: Recent Developments

Extremozymes combine high specificity and sensitivity with the ability to withstand extreme operational conditions. This work presents an overview of extremozymes that show potential for environmental monitoring devices and outlines the latest advances in biosensors utilizing these unique molecules. The characteristics of various extremozymes described so far are presented, underlining their stability and operational conditions that make them attractive for biosensing. The biosensor design is discussed based on the detection of photosynthesis-inhibiting herbicides as a case study. Several biosensors for the detection of pesticides, heavy metals, and phenols are presented in more detail to highlight interesting substrate specificity, applications or immobilization methods. Compared to mesophilic enzymes, the integration of extremozymes in biosensors faces additional challenges related to lower availability and high production costs. The use of extremozymes in biosensing does not parallel their success in industrial applications. In recent years, the "collection" of recognition elements was enriched by extremozymes with interesting selectivity and by thermostable chimeras. The perspectives for biosensor development are exciting, considering also the progress in genetic editing for the oriented immobilization of enzymes, efficient folding, and better electron transport. Stability, production costs and immobilization at sensing interfaces must be improved to encourage wider applications of extremozymes in biosensors.

Advances in identifying and managing emerging contaminants in aquatic ecosystems: Analytical approaches, toxicity assessment, transformation pathways, environmental fate, and remediation strategies

Emerging contaminants (ECs) are increasingly recognized as threats to human health and ecosystems. This review evaluates advanced analytical methods, particularly mass spectrometry, for detecting ECs and understanding their toxicity, transformation pathways, and environmental distribution. Our findings underscore the reliability of current techniques and the potential of upcoming methods. The adverse effects of ECs on aquatic life necessitate both in vitro and in vivo toxicity assessments. Evaluating the distribution and degradation of ECs reveals that they undergo physical, chemical, and biological transformations. Remediation strategies such as advanced oxidation, adsorption, and membrane bioreactors effectively treat EC-contaminated waters, with combinations of these techniques showing the highest efficacy. To minimize the impact of ECs, a proactive approach involving monitoring, regulations, and public education is vital. Future research should prioritize the refining of detection methods and formulation of robust policies for EC management.

Comparative homology of Pleurotus ostreatus laccase enzyme: Swiss model or Modeller?

Laccases stand out in the industrial context due to their versatile biotechnological applications. Although these enzymes are frequently investigated, currently, Pleurotus ostreatus laccase structural model is unknown. Therefore, this research aims to predict and validate a P. ostreatus laccase theoretical model by means of comparative homology. The laccase target's primary structure (AOM73725.1) was obtained from the NCBI database, the model was predicted from homologous structures obtained from the PDB (PDB-ID: 5A7E, 2HRG, 4JHU, 1GYC) using the Swiss-Model and Modeller, and was refined in GalaxyRefine. The models were validated using PROCHECK, VERIFY 3D, ERRAT, PROVE and QMEAN Z-score servers. Moreover, molecular docking between the laccase model (Lacc4MN) and ABTS was performed on AutoDock Vina. The models that were generated by the Modeller showed superior stereochemical and structural characteristics to those predicted by the Swiss Model. The refinement made it difficult to stabilize the copper atoms which are typical of laccases. The Lacc4MN model showed the interactions between the amino acids in the active site of the laccase and the copper atoms, thereby hinting the stabilization of the metal through electrostatic interactions with histidine and cysteine. The molecular docking between Lacc4MN and ABTS showed negative free energy and the formation of two hydrogen bonds involving the amino acids ASP 208 and GLY 268, and a Pi-sulfur bond between residue HIS 458 and ABTS, which demonstrates the typical catalytic functionality of laccases. Furthermore, the theoretical model Lacc4MN presented stereochemical and structural characteristics that allow its use in silico tests.Communicated by Ramaswamy H. Sarma.

Construction of bacterial laccase displayed on the microbial surface for ultrasensitive biosensing of phenolic pollutants with nanohybrids-enhanced performance

Although bacterial laccase (BLac) has many advantages including short fermentation period and adaptable activity to wide temperature and pH ranges, it is of challenge and significance to apply BLac to the biosensors, due to the intracellular secretion and poor electron transfer efficiency of BLac. Here, cell surface-displayed BLac (CSDBLac) was successfully constructed as whole-cell biocatalyst through microbial surface display technology, eliminating the mass transfer restriction and laborious purification steps. Meanwhile, MXenes/polyetherimide-multiwalled carbon nanotubes (MXenes/PEI-MWCNTs) nanohybrids were designed to immobilize CSDBLac and improve their electrochemical activity. Then, an electrochemical biosensor was successfully constructed to detect common phenolic pollutants (catechol and hydroquinone) by the co-immobilization of CSDBLac and MXenes/PEI-MWCNTs nanohybrids onto a glassy carbon electrode. Subsequently, it was successfully applied to the water samples assay with good reliability and repeatability. This work innovatively used BLac and nanohybrid as the core elements of biosensor, which not only effectively solved the application bottleneck of BLac on biosensors, but also dramatically promote the electro transfer efficiency between whole-cell biocatalyst and electrode. This method is of profound meanings for significantly improving the performance of phenolic biosensors and other biosensors from the origin.

Recent innovations and challenges in the eradication of emerging contaminants from aquatic systems

Presence of emerging pollutants (EPs), aka Micropollutants (MPs) in the freshwater environments is a severe threat to the environment and human beings. They include pharmaceuticals, insecticides, industrial chemicals, natural hormones, and personal care items and the pollutants are mostly present in wastewater generated from urbanization and increased industrial growth. Even concentrations as low as ngL^-1 or mgL^-1 have proven ecologically lethal to aquatic biota. For several years, the biodegradation of various Micropollutants (MPs) in aquatic ecosystems has been a significant area of research worldwide, with many chemical compounds being discovered in various water bodies. As aquatic biota spends most of their formative phases in polluted water, the impacts on aquatic biota are obvious, indicating that the environmental danger is substantial. In contrast, the impact of these contaminants on aquatic creatures and freshwater consumption is more subtle and manifests directly when disrupting the endocrine system. Research and development activities are expected to enable the development of ecologically sustainable, cost-effective, and efficient treatments for practical systems in the near future. Therefore, this review aims to understand recent emerging pollutants discovered and the available treatment technologies and suggest an innovative and cost-effective method to treat these EPs, which is sustainable and follows the circular bioeconomy.

Bio-removal of emerging pollutants by advanced bioremediation techniques

This review highlights the relevance of bioremediation techniques for the removal of emerging pollutants (EPs). The EPs are chemical or biological pollutants that are not currently monitored or regulated by environmental authorities, but which can enter the environment and cause harmful effects to the environment and human health. In recent times, an ample range of EPs have been found in water bodies, where they can unbalance ecosystems and cause negative effects on non-target species. In addition, some EPs have shown high rates of bioaccumulation in aquatic species, thus affecting the safety and quality of seafood. The negative impacts of emerging pollutants, their wide distribution in the environment, their bioaccumulation rates, and their resistance to wastewater treatment plants processes have led to research on sustainable remediation. Remediation techniques have been recently directed to advanced biological remediation technologies. Such technologies have exhibited numerous advantages like in-situ remediation, low costs, eco-friendliness, high public acceptance, and so on. Thus, the present review has compiled the most recent studies on bioremediation techniques for water decontamination from emerging pollutants to extend the current knowledge on sustainable remediation technologies. Biological emerging contaminants, agrochemicals, endocrine-disrupting chemicals, and pharmaceutical and personal care products were considered for this review study, and their removal by bioremediation techniques involving plants, bacteria, microalgae, and fungi. Finally, further research opportunities are presented based on current challenges from an economic, biological, and operation perspective.