Integrating metal-organic framework ZIF-8 with green modifier empowered bacteria with improved bioremediation

Mixed organic acids as an effective green modifier for enhancing PAH degradation by ZIF-8@ B. subtilis ZL09-26

Although a protective shell based on a metal-organic framework (MOF) can effectively improve the remediation of polycyclic aromatic hydrocarbons (PAHs) by microorganisms, the functional characteristics of the shell are often limited by the surface charge, chemical properties and intrinsic strain characteristics. This study explored the potential of mixed organic acids (MA) as an eco-friendly modifier for zeolite imidazolate framework-8 (ZIF-8), facilitating the formation of a biomimetic mineralized shell around Bacillus subtilis ZL09-26. The addition of MA into the ZIF-8 protective shell was found to stimulate growth and bolster cell viability. Notably, adding MA contribute resulted in a 1.98- fold enhancement of the PHE degradation efficiency. After five cycles of reuse, ZIF-8-MA@B. subtilis ZL09-26 still maintained almost 90 % of the initial PHE degradation ability. Proteomic analysis revealed a coordinated regulation of multiple metabolic pathways that facilitated PHE uptake and degradation, including central carbon metabolism, direct PHE biodegradation, oxidative phosphorylation, aminoacyl-tRNA biosynthesis, fatty acid biosynthesis, ABC transporters, and the biosynthesis of valine, leucine, isoleucine, and lysine. This work broadens the application potential of biomineralized microorganisms, providing novel strategies for the sustainable bioremediation of xenobiotic pollutants in the environment.

Cyborg microbe biohybrids with metal-organic coating layers: Strategies, functionalisation and potential applications

The integration of living microbes, specifically bacteria and fungi, with metal-organic nanocoatings has led to the recent development of cyborg microbe biohybrids, which show excellent adaptability and functionality for a wide range of potential applications in biotechnology and medicine. This review discusses the strategies, functionalisation, and applications of these biohybrids, which are categorised into two types of coatings: metal-organic frameworks (MOFs) and metal-phenolic networks (MPNs). Key advances in their synthetic approaches via in-situ and pre-synthesised coatings are crucially addressed, and yet the methodology details and specific advantages are highlighted. Despite the notable advancements, there are various limitations and challenges, such as determination of the long-term viability and stability of the biohybrids, insufficient work on their theranostic applications and essentially scaling-up difficulties for industrial and clinical translation. The latest advancements in the biohybrids and related technology have established a critical foundation for enhancing innovative studies through the strong interdisciplinary teamwork.

Nanomaterial-mediated strategies for enhancing bioremediation of polycyclic aromatic hydrocarbons: A systematic review

Polycyclic aromatic hydrocarbons (PAHs) are pervasive organic pollutants in the environment that are formed as an outcome of partial combustion of organic matter. PAHs pose a significant threat to ecological systems and human health due to their cytotoxic and genotoxic effects. Therefore, an immediate need for effective PAH remediation methods is crucial. Although nanomaterials are effective for remediation of PAHs, concerns regarding environmental compatibility and sustainability remains. Therefore, this study emphasizes integration of nanomaterials with bioremediation methods, which might offer a more sustainable and ecofriendly approach to PAHs remediation. A systematic search was conducted through scholarly databases from 2013 to 2023. A total of 360 articles were scrutinized, among which 26 articles were selected that resonated with the application of nano-bioremediation. These literatures comprise both comparative analysis of bioremediation only as well as nano-bioremediation. There is an elevation of 18.9 % in PAHs removal of liquid-phase samples, when comparing bioremediation (52.2 %) with nano-bioremediation (71.1 %). A consistent trend was observed in soil samples, with bioremediation and nano-bioremediation that successfully remove PAHs, with 60.8 % and 75.1 % respectively, indicating a 14.3 % improvement. Furthermore, the review elaborated on the various features of nanomaterials that led to their efficiency in the bioremediation of PAH. The review also discussed the strategies of nano-bioremediation namely nanomaterial-assisted microbial degradation, nanomaterial-assisted enzyme-enhanced microbial activity, nanomaterial-immobilized microbial cells, nanomaterial-facilitated electron transfer, and even some eco-green approaches to remediate PAHs, like biogenic nanomaterial for PAHs.

A polymer deposition-mediated surface-charge reformation strategy: reversing the MOF biomineralization behavior

Biomineralization of a porous metal-organic framework (MOF) shell onto biomacromolecule templates is a burgeoning strategy to construct robust biocatalysts. However, it strongly relies on the interfacial interaction between MOF precursors and enzyme surface, significantly limiting the generalization of this nanotechnology. Herein, we identify polymers that are well-suited for deposition onto target biomacromolecules via supramolecular interactions and introduce a polymer deposition-mediated surface-charge reformation strategy to facilitate the biomineralization of porous MOFs, including ZIF-8, ZIF-90, and ZIF-zni onto enzymes. We investigate nine commercially available polymers to find that those with dense -SO3H and -COOH groups effectively regulate the surface-charge properties of the enzymes that are unfavorable for biomineralization. The polymer-enzyme complex thus formed retains its original bioactivity and offers significantly elevated sites to accumulate metal precursors, triggering the in-place MOF biomineralization. We demonstrate that this approach allows access to diverse MOF biocatalysts independent of the enzyme surface chemistry, which are difficult to be synthesized by previous biomineralization methods. Given the highly specific bioactivity and structural stability of the MOF biocatalysts, a chemiluminiscence sensor platform is developed for the sensitive detection of hydrogen sulfide (H2S) biomarkers, with a low limit of detection of 0.09 nM that is superior to most of the reported methods. This study provides an effective and universal strategy for MOF biomineralization using fragile enzymes as biotemplates and offers new insights into accessing multifunctional MOF hybrid biocatalysts.

Deep eutectic solvent-functionalized amorphous UiO-66 for efficient extraction and ultrasensitive analysis of perfluoroalkyl substances in infant milk powder

In this study, a convenient and effective method for determination of perfluoroalkyl substances (PFASs) in infant formula was developed based on a novel dispersive solid-phase extraction using deep eutectic solvent-functionalized amorphous UiO-66 (DES/aUiO-66) as sorbent. The synthesis of materials could be achieved without the use of complex and environmentally unfriendly procedures. Parameters were systematically investigated to establish a simple, fast, and efficient green pretreatment method. The method demonstrated high sensitivity, good precision, a detection limit of 0.330-0.529 ng·kg-1, and low matrix effects (< 12.8%). The mechanism for this material was elucidated by ab initio molecular dynamics (AIMD) simulations and quantum chemistry calculations. The presence of massive pore structures and collectively synergistic binding sites facilitated affinity adsorption toward PFASs. Finally, this method was applied to the monitoring of PFASs in 10 actual milk powder samples. This groundbreaking approach opens new possibilities for the advancement of analytical techniques and food safety monitoring.

New insights into the concentration-dependent regulation of membrane biofouling formation via continuous nanoplastics stimulation

The release of nanoplastics (NPs) into the environment is growing due to the extensive use of plastic products. Numerous studies have confirmed the negative effects of NPs on microorganisms, which poses uncertainties concerning their impact on nanofiltration (NF) membrane biofouling. This study investigated the initial cell adhesion process, NF membrane biofouling kinetic processes and bacterial responses of Pseudomonas aeruginosa (P. aeruginosa) exposed to varied NPs concentrations (0-50 mg·L-1). Transcriptome analysis demonstrated that low concentration of NPs (0.1 mg·L-1) promoted bacterial quorum sensing, energy metabolism, exopolysaccharide biosynthesis and bacterial secretion systems. Correspondingly, the polysaccharide content increased remarkably to 2.77 times the unexposed control, which served as a protective barrier for bacteria to avoid the impact of NPs-induced stress. Suppressed homologous recombination, microbial metabolic potentials and flagellar assembly were detected in bacteria exposed to a high concentration (50 mg·L-1) of NPs, mainly due to the triggered reactive oxygen species (ROS) generation, genomic DNA damage, and decreased energy production. Overall, enhanced formation of the extracellular polymeric substances (EPS) and aggravated membrane flux decline were observed when NPs interacted with the membrane surface by cell secretions (low NPs levels) or cell lysis (high NPs levels). These findings shed light on understanding the microbial metabolism mechanism and membrane biofouling propensity with NPs stress at both the molecular and gene levels.