Revisiting Solar Energy Flow in Nanomaterial-Microorganism Hybrid Systems.

Nanomaterial-microorganism hybrid systems (NMHSs), integrating semiconductor nanomaterials with microorganisms, present a promising platform for broadband solar energy harvesting, high-efficiency carbon reduction, and sustainable chemical production. While studies underscore its potential in diverse solar-to-chemical energy conversions, prevailing NMHSs grapple with suboptimal energy conversion efficiency. Such limitations stem predominantly from an insufficient systematic exploration of the mechanisms dictating solar energy flow. This review provides a systematic overview of the notable advancements in this nascent field, with a particular focus on the discussion of three pivotal steps of energy flow: solar energy capture, cross-membrane energy transport, and energy conversion into chemicals. While key challenges faced in each stage are independently identified and discussed, viable solutions are correspondingly postulated. In view of the interplay of the three steps in affecting the overall efficiency of solar-to-chemical energy conversion, subsequent discussions thus take an integrative and systematic viewpoint to comprehend, analyze and improve the solar energy flow in the current NMHSs of different configurations, and highlighting the contemporary techniques that can be employed to investigate various aspects of energy flow within NMHSs. Finally, a concluding section summarizes opportunities for future research, providing a roadmap for the continued development and optimization of NMHSs.

Photocatalytic Bacterial Inactivation by a Rape Pollen-MoS2 Biohybrid Catalyst: Synergetic Effects and Inactivation Mechanisms.

A novel and efficient 3D biohybrid photocatalyst, defective MoS2 nanosheets encapsulated carbonized rape pollen, was fabricated and applied to water disinfection. The rape pollen-MoS2 (PM) biohybrid showed excellent dispersibility, high stability, and efficient charge-carrier separation and migration ability, resulting in the highly enhanced photocatalytic inactivation performance toward various waterborne bacteria under different light sources. The inactivation mechanisms were systematically investigated. Reactive species (RSs), including electrons, holes, and reactive oxygen species (•O2- and •OH), played major roles in inactivating bacteria. The antioxidant system of bacteria exhibited a self-protection capacity by eliminating the photogenerated RSs from PM biohybrid at the early stage of inactivation. With the accumulation of RSs, the cell membrane and membrane-associated functions were destroyed, as suggested by the collapse of cell envelope and subsequent loss of cell respiration and ATP synthesis capacity. The microscopic images further confirmed the destruction of the bacterial membrane. After losing the membrane barrier, the oxidation of cytoplasmic proteins and lipids caused by invaded RSs occurred readily. Finally, the leakage of DNA and RNA announced the irreversible death of bacteria. These results indicated that the bacterial inactivation began with the membrane rupture, followed by the oxidation and leakage of intracellular substances. This work not only provided a new insight into the combination of semiconductors with earth-abundant biomaterials for fabricating high-performance photocatalysts, but also revealed the underlying mechanisms of photocatalytic bacterial inactivation in depth.

In situ mycoremediation of acid rain and heavy metals co-contaminated soil through microbial inoculation with Pleurotus ostreatus.

The combined pollution of acid rain and heavy metals in soil is a pressing environmental problem, especially in the regions with large-scale heavy industrial production activities. Low remediation efficiency and weak long-lasting stability are major challenges when disposing the heavy metals contaminated soil in acid rain polluted sites. Herein, a specific microbe, strain CT13 was isolated and domesticated to exhibit high tolerance to both acid rain and cadmium (Cd). Then, an in situ mycoremediation method by adopting a bioaugmentation technology of strain CT13 inoculation with Pleurotus ostreatus was developed. The remediation performance was investigated in acidic conditions with Cd concentrations in soil ranging from 0 to 15 mg/kg. While most of the bacteria strains (e.g. strain CT6/13) significantly improved the dry weight of mushroom and Cd accumulation in neutral environment, the performance of strain CT6 was remarkably deteriorated in acid rain environment. In contrast, strain CT13 maintained its behavior in acidic conditions, displaying ∼30 % and 150 % enhancements (vs the neutral environment) in the dry weight of mushroom and Cd accumulation, respectively. In addition, inoculation of strain CT13 led to significant reductions in the content of superoxide dismutase, peroxidase and lipid peroxidation in the fruiting body of P. ostreatus, indicating an improvement in the mushroom's tolerance to both acid rain and heavy metals. The synergistic effect of strain CT13 and P. ostreatus realized the significant improvement in soil remediation efficiency and long-lasting stability in acidic conditions, providing valuable insights into the remediation of heavy metal contaminated soil in the regions affected by acid rain.

A Self-Assembled MOF-Escherichia Coli Hybrid System for Light-Driven Fuels and Valuable Chemicals Synthesis.

The development of semi-artificial photosynthetic systems, which integrate metal-organic frameworks (MOFs) with industrial microbial cell factories for light-driven synthesis of fuels and valuable chemicals, represents a highly promising avenue for both research advancements and practical applications. In this study, an MOF (PCN-222) utilizing racemic-(4-carboxyphenyl) porphyrin and zirconium chloride (ZrCl4) as primary constituents is synthesized. Employing a self-assembly process, a hybrid system is constructed, integrating engineered Escherichia coli (E. coli) to investigate light-driven hydrogen and lysine production. These results demonstrate that the light-irradiated biohybrid system efficiently produce H2 with a quantum efficiency of 0.75% under full spectrum illumination, the elevated intracellular reducing power NADPH is also observed. By optimizing the conditions, the biohybrid system achieves a maximum lysine production of 18.25 mg L-1, surpassing that of pure bacteria by 332%. Further investigations into interfacial electron transfer mechanisms reveals that PCN-222 efficiently captures light and facilitates the transfer of photo-generated electrons into E. coli cells. It is proposed that the interfacial energy transfer process is mediated by riboflavin, with facilitation by secreted small organic acids acting as hole scavengers for PCN-222. This study establishes a crucial foundation for future research into the light-driven biomanufacturing using E. coli-based hybrid systems.

Vacancy-rich BiO2-x as a highly-efficient persulfate activator under near infrared irradiation for bacterial inactivation and mechanism study.

This study, for the first time, developed a novel defective BiO2-x based collaborating system, where the near-infrared light (NIR) irradiation (λ > 700 nm) initiated persulfate activation and photocatalytic bacterial inactivation simultaneously. Vacancy-rich BiO2-x nanoplates possessed impressive NIR absorption and firstly realized persulfate activation under NIR irradiation. In this collaborating system, on one hand, the persulfate can be transformed into sulfate radicals through light/heat activation mode directly, which would be enhanced by the presence of vacancy-rich BiO2-x owing to its outstanding light and heat absorption ability. On the other hand, the photogenerated electrons can further efficiently react with persulfate and form sufficient reactive sulfate radicals. The sulfate radicals, synergizing with other reactive species (O2-, h+, etc.), achieved a 7-log Escherichia coli inactivation within 40 min. The systematic investigation of inactivation mechanism revealed that the reactive species caused the dysfunction of cellular respiration, ATP synthesis and bacterial membrane, followed by the severely oxidative damage to the antioxidative SOD and CAT enzymes and the generation of carbonylated protein. The final leakage of DNA and RNA implied the lethal damage to the bacteria cells. This work provided a new insight into the persulfate associated NIR driven remediation technology of controlling microbial contaminants.

Hydrogen Peroxide Production from Water Oxidation on a CuWO4 Anode in Oxygen-Deficient Conditions for Water Decontamination.

Hydrogen peroxide, an environmentally benign oxidant, is an effective chemical agent for water purification. On-site production of H2O2 is considered economical because it avoids the cost of storage and transportation. Traditional generation of H2O2 from oxygen reduction, as a heterogeneous electrochemical reaction, suffers from mass transfer problems because of the limited solubility and low diffusion rate of oxygen in water. These limitations can be overcome if H2O2 is formed by water oxidation. Herein, conversion of water to hydrogen peroxide was achieved efficiently on a CuWO4 anode. This water oxidation strategy can generate H2O2 at a rate of ∼11.8 µmol min-1 cm-2 at 3.0 V versus reversible hydrogen electrode. Importantly, this on-site H2O2 production shows high efficiency in water purification in O2-deficient conditions. This water oxidation anode offers a feasible way to provide a green purification agent with only water as the final byproduct, avoiding toxic intermediates and residues during the production and application.

Bioremediation of Crude Glycerol by a Sustainable Organic-Microbe Hybrid System.

Klebsiella pneumoniae with crude glycerol-utilizing and hydrogen (H2)-producing abilities was successfully isolated from return activated sludge from Shatin Sewage Treatment Works. The H2 production strategy used in this study was optimized with crude glycerol concentrations, and 1,020 µmol of H2 was generated in 3 h. An organic-microbe hybrid system was constructed with metal-free hydrothermal carbonation carbon (HTCC) microspheres to enhance the H2 production under visible light (VL) irradiation. Under optimized VL intensity and HTCC concentration, an elevation of 35.3% in H2 production can be obtained. Electron scavenger study revealed that the photogenerated electrons (e-) from HTCC contributed to the additional H2 production. The variation in intercellular intermediates, enzymatic activity, and reducing equivalents also suggested that the photogenerated e- interacted with K. pneumoniae cells to direct the metabolic flux toward H2 production. This study demonstrated the feasibility of using an organic-microbe hybrid system as a waste-to-energy technology.

Mechanisms into the removal and translocation of cadmium by Oudemansiella radicata in soil.

This study investigated the removal and translocation mechanism of cadmium (Cd) by Oudemansiella radicata (O. radicata) in mushroom-soil rhizosphere and the fruiting body of mushroom. For this, the biomass, physiochemical parameters, and Cd distribution of O. radicata were examined in the soil spiked with 0, 10, 20, and 30 mg kg-1 Cd. The soil microecology and the Cd fractionation in the soil rhizosphere were also measured. Results showed that, O. radicata possesses high capability to tolerate Cd, although its surface phenotypic structure was influenced by high concentrations of Cd. The observed concentrations of Cd in O. radicata were in the following order: root (the part of stipe in soil) > pileus > stipe. The presence of Cd led to an increase in the production of antioxidant enzymes and glutathione (GSH). These results suggested that antioxidant enzymes and GSH assisted detoxification and accumulation of Cd within the mushroom. Meanwhile, in the soil rhizosphere, the concentrations of oxalic, citric, and malic acids were enhanced with the treatment of Cd, indicating that the production of these acids was closely related to the presence of Cd in soils. Additionally, the proportion of acid-soluble Cd was increased and the soil microecology (microbial counts, urease, and acid phosphatase activities) also enhanced with the inoculation of O. radicata. Overall, this study demonstrated that O. radicata is a promising candidate for the remediation of Cd-contaminated soil.

Effects of amendments on heavy metal immobilization and uptake by Rhizoma chuanxiong on copper and cadmium contaminated soil.

An improved method was applied for remediating cadmium and copper co-contaminated soil and reducing the metal concentration in Rhizoma chuanxiong. Pot experiments were conducted with six amendments (composed with bentonite, phosphate, humic acid, biochar, sepiolite powder, etc.). The results showed that soil pH, biological activities (soil enzymatic activities and microbial counts) and R. chuanxiong biomass were greatly improved with the addition of amendments in all treatments, especially in T3 and T6. Also, amendments effectively decreased the concentration of malondialdehyde and H2O2 in R. chuanxiong. In the T3 treatment, the bio-available Cd and Cu in soil were significantly decreased by 0.53 and 0.41 mg kg-1, respectively. Meanwhile, the amendment in T3 reduced Cd and Cu accumulation in R. chuanxiong about 45.83 and 39.37%, respectively, compared to T0. Moreover, the Fourier transform infrared spectroscopy spectra showed the surface functional groups of every amendment. To conclude, this study offers an effective and environmental method to reduce metal accumulation in R. chuanxiong on heavy metal co-contaminated soil.

Remediation Performance and Mechanism of Heavy Metals by a Bottom Up Activation and Extraction System Using Multiple Biochemical Materials.

Soil contamination with heavy metals has caused serious environmental problems and increased the risks to humans and biota. Herein, we developed an effective bottom up metals removal system based on the synergy between the activation of immobilization metal-resistant bacteria and the extraction of bioaccumulator material (Stropharia rugosoannulata). In this system, the advantages of biochar produced at 400 °C and sodium alginate were integrated to immobilize bacteria. Optimized by response surface methodology, the biochar and bacterial suspension were mixed at a ratio of 1:20 (w:v) for 12 h when 2.5% sodium alginate was added to the mixture. Results demonstrated that the system significantly increased the proportion of acid soluble Cd and Cu and improved the soil microecology (microbial counts, soil respiration, and enzyme activities). The maximum extractions of Cd and Cu were 8.79 and 77.92 mg kg-1, respectively. Moreover, details of the possible mechanistic insight into the metal removal are discussed, which indicate positive correlation with the acetic acid extractable metals and soil microecology. Meanwhile, the "dilution effect" in S. rugosoannulata probably plays an important role in the metal removal process. Furthermore, the metal-resistant bacteria in this system were successfully colonized, and the soil bacteria community were evaluated to understand the microbial diversity in metal-contaminated soil after remediation.