Multi-functional organic gelator derived from phenyllactic acid for phenol removal and oil recovery

SERS-based microdroplet platform for high-throughput screening of Escherichia coli strains for the efficient biosynthesis of D-phenyllactic acid

D-Phenyllactic acid (D-PLA) is a potent antimicrobial typically synthesized through chemical methods. However, due to the complexity and large pollution of these reactions, a simpler and more eco-friendly approach was needed. In this study, a strain for D-PLA biosynthesis was constructed, but the efficiency was restricted by the activity of D-lactate dehydrogenase (DLDH). To address this issue, a DLDH mutant library was constructed and the Surface-Enhanced Raman Spectroscopy (SERS) was employed for the precise quantification of D-PLA at the single-cell level. The TB24 mutant exhibited a significant improvement in D-PLA productivity and a 23.03-fold increase in enzymatic activity, which was attributed to the enhanced hydrogen bonding and increased hydrophobicity within the substrate-binding pocket. By implementing multi-level optimization strategies, including the co-expression of glycerol dehydrogenase (GlyDH) with DLDH, chassis cell replacement, and RBS engineering, a significant increase in D-PLA yields was achieved, reaching 128.4 g/L. This study underscores the effectiveness of SERS-based microdroplet high-throughput screening (HTS) in identifying superior mutant enzymes and offers a strategy for large-scale D-PLA biotransformation.

Experimental Evaluation of Performance of a Low-Initial-Viscosity Gel Flooding System

In order to effectively adjust reservoir heterogeneity and further exploit the remaining oil, a new type of low-viscosity gel was prepared by adding a regulating agent, retarder, and reinforcing agent on the basis of a polymer + Cr3+ crosslinking system. The new gel has the advantages of low initial viscosity, a slow gel formation rate, and high strength after gel formation. The effectiveness of the gel was verified through three-layer core displacement experiments, and the injection scheme was optimized by changing the slug combination of the polymer and the gel. The results showed that the gel can effectively block the high-permeability layer and adjust reservoir heterogeneity. An injection of 0.1 pore volume (PV) low-initial-viscosity gel can improve oil recovery by 5.10%. By changing the slug combination of the gel and polymer, oil recovery was further increased by 3.12% when using an injection of 0.07 PV low-initial-viscosity gel +0.2 PV high-concentration polymer +0.05 PV low-initial-viscosity gel +0.5 PV high-concentration polymer.

Reusable Solid-form Phase-Selective Organogelators for Rapid and Efficient Remediation of Crude Oil Spill

Phase-selective organogelators (PSOGs) are considered as a prospective tool for their application in oil spill remediation. However, the number of reports on the PSOGs that can be used in powder form for prompt phase-selective gelation of crude oils is still limited. In this study, a series of compounds with l-mandelic acid as the scaffold bearing different amino acid fragments have been prepared. Also, the gelation behaviors and properties of these derivatives toward organic liquids, product oils, and a type of Chinese crude oil were investigated via heating-and-cooling process, stirring, or resting operation. Besides, the micromorphologies of the resulting gels and the driving forces for the gel formation have been studied by scanning electron microscopy, Fourier transform infrared, UV spectroscopy, concentration-dependent 1H NMR, and X-ray diffraction. Particularly, gelator C15-Phe-Mac-Nap was shown to have the capability of congealing the Chinese crude oil selectively from water in powder form with a relatively lower gelator dosage, as compared with the other gelators we reported in the current and previous works. Moreover, gelator C15-Phe-Mac-Nap displayed some advantageous behaviors such as the reusability of gelator, excellent mechanical and chemical stability of the crude oil gels, and nontoxicity of the gelator in the aquatic environment, indicating its great potential application value for marine oil spill remediation.

Recent development of phenyllactic acid: physicochemical properties, biotechnological production strategies and applications

Phenyllactic acid (PLA) is capable of inhibiting the growth of many microorganisms, showing a broad-spectrum antimicrobial property, which allows it to hold vast applications in the: food, feed, pharmaceutical, and cosmetic industries, especially in the field of food safety. Recently, the production of PLA has garnered considerable attention due to the increasing awareness of food safety from the public. Accordingly, this review mainly updates the recent development for the production of PLA through microbial fermentation and whole-cell catalysis (expression single-, double-, and triple-enzyme) strategies. Firstly, the: physicochemical properties, existing sources, and measurement methods of PLA are systematically covered. Then, the inhibition spectrum of PLA is summarized, and synchronously, the antimicrobial and anti-biofilm mechanisms of PLA on commonly pathogenic microorganisms in foods are described in detail, thereby clarifying the reason for extending the shelf life of foods. Additionally, the factors affecting the production of PLA are summarized from the biosynthesis and catabolism pathway of PLA in microorganisms, as well as external environmental parameters insights. Finally, the downstream treatment process and applications of PLA are discussed and outlined. In the future, clinical data should be supplemented with the metabolic kinetics of PLA in humans and to evaluate animal toxicology, to enable regulatory use of PLA as a food additive. A food-grade host, such as Bacillus subtilis and Lactococcus lactis, should also be developed as a cell vector expressing enzymes for PLA production from a food safety perspective.

Coenzyme self-sufficiency system-recent advances in microbial production of high-value chemical phenyllactic acid

Phenyllactic acid (PLA), a natural antimicrobial substance, has many potential applications in the food, animal feed, pharmaceutical and cosmetic industries. However, its production is limited by the complex reaction steps involved in its chemical synthesis. Through advances in metabolic engineering and synthetic biology strategies, enzymatic or whole-cell catalysis was developed as an alternative method for PLA production. Herein, we review recent developments in metabolic engineering and synthetic biology strategies that promote the microbial production of high-value PLA. Specially, the advantages and disadvantages of the using of the three kinds of substrates, which includes phenylpyruvate, phenylalanine and glucose as starting materials by natural or engineered microbes is summarized. Notably, the bio-conversion of PLA often requires the consumption of expensive coenzyme NADH. To overcome the issues of NADH regeneration, efficiently internal cofactor regeneration systems constructed by co-expressing different enzyme combinations composed of lactate dehydrogenase with others for enhancing the PLA production, as well as their possible improvements, are discussed. In particular, the construction of fusion proteins with different linkers can achieve higher PLA yield and more efficient cofactor regeneration than that of multi-enzyme co-expression. Overall, this review provides a comprehensive overview of PLA biosynthesis pathways and strategies for increasing PLA yield through biotechnology, providing future directions for the large-scale commercial production of PLA and the expansion of downstream applications.

Carboxylate Group-Based Phase-Selective Organogelators with a pH-Triggered Recyclable Property

Phase-selective organogelators (PSOGs) have recently attracted more attention because of their advantages in handling oil spills and leaked organic solvents. However, it is difficult to separate and recover the organic phase and PSOGs from organic gels due to the strong interaction between them. Aiming to enhance the separation and recovery performance of the organic phase and PSOGs, we synthesized a series of pH-responsive PSOGs by using itaconic anhydride and fatty amines with carbon chain lengths of C₁₂-C₁₈. Here, PSOGs have an excellent gelation ability in that amounts of organic solvents and fuel oil can be solidified at a low concentration (<3 wt %). It is worth noting that these gels are stronger, which is more convenient for removal by a salvage operation. More importantly, compared with traditional organogelators, pH-responsive PSOGs can easily recover the organic phase and fuel oil with an adjustment of the pH without extraction or distillation. Because of the transformation between the hydrophilicity and hydrophobicity of PSOGs by pH stimulation, 83.15% PSOGs are recovered in three-cycle experiments. In addition, the recycled PSOGs can be used to realize the removal of the organic phase again. Herein, we find that pH-responsive PSOGs could be used as promising and sustainable materials for separating and recovering organic solvents/oils and PSOGs.

Using Unnatural Protein Fusions to Engineer a Coenzyme Self-Sufficiency System for D-Phenyllactic Acid Biosynthesis in Escherichia coli

The biosynthetic production of D-penyllactic acid (D-PLA) is often affected by insufficient supply and regeneration of cofactors, leading to high production cost, and difficulty in industrialization. In this study, a D-lactate dehydrogenase (D-LDH) and glycerol dehydrogenase (GlyDH) co-expression system was constructed to achieve coenzyme NADH self-sufficiency and sustainable production of D-PLA. Using glycerol and sodium phenylpyruvate (PPA) as co-substrate, the E. coli BL21 (DE3) harboring a plasmid to co-express LfD-LDH and BmGlyDH produced 3.95 g/L D-PLA with a yield of 0.78 g/g PPA, similar to previous studies. Then, flexible linkers were used to construct fusion proteins composing of D-LDH and GlyDH. Under the optimal conditions, 5.87 g/L D-PLA was produced by expressing LfD-LDH-l3-BmGlyDH with a yield of 0.97 g/g PPA, which was 59.3% increased compared to expression of LfD-LDH. In a scaled-up reaction, a productivity of 5.83 g/L/h was reached. In this study, improving the bio-catalytic efficiency by artificial redox self-equilibrium system with a bifunctional fusion protein could reduce the bio-production cost of D-PLA, making this bio-production of D-PLA a more promising industrial technology.

Two-Dimensional Infrared Correlation Spectroscopy, Conductor-like Screening Model for Real Solvents, and Density Functional Theory Study on the Adsorption Mechanism of Polyvinylpolypyrrolidone for Effective Phenol Removal in an Aqueous Medium

The discharge of industrial effluents, such as phenol, into aquatic and soil environments is a global problem due to its serious negative impacts on human health and aquatic ecosystems. In this study, the ability of polyvinylpolypyrrolidone (PVPP) to remove phenol from an aqueous medium was investigated. The results showed that a significant proportion of phenol (up to 74.91%) was removed using PVPP at pH 6.5. Isotherm adsorption experiments of phenol on PVPP indicated that the best-fit adsorption was obtained using Langmuir models. The response peaks of the hydroxyl groups of phenol (OH) and the carboxyl groups (i.e., C=O) of PVPP were altered, indicating the formation of a hydrogen bond between the PVPP and phenol during phenol removal, as characterized using 1D and 2D IR spectroscopy. The resulting complexes were successfully characterized based on their thermodynamic properties, Mulliken charge, and electronic transition using the DFT approach. To clarify the types of interactions taking place in the complex systems, quantum theory of atoms in molecules (QTAIM) analysis, reduced density gradient noncovalent interaction (RDG-NCI) approach, and conductor-like screening model for real solvents (COSMO-RS) approach were also successfully calculated. The results showed that the interactions that occurred in the process of removing phenol by PVPP were through hydrogen bonding (based on RDG-NCI and COSMO-RS), which was identified as an intermediate type (∇2ρ(r) > 0 and H < 0, QTAIM). To gain a deeper understanding of how these interactions occurred, further characterization was performed based on adsorption mechanisms using molecular electrostatic potential, global reactivity, and local reactivity descriptors. The results showed that during hydrogen bond formation, PVPP acts as a nucleophile, whereas phenol acts as an electrophile and the O9 atom (i.e., donor electron) reacts with the H22 atom (i.e., acceptor electron).

A tertiary amine group-based organogelator with pH-trigger recyclable property

The separation and recovery of oils and organogelators can be easily realized by tuning the pH value.

Evaluating the role of a urea-like motif in enhancing the thermal and mechanical strength of supramolecular gels

Enhanced thermal and mechanical strength in semicarbazone gels with a urea-like motif obtained by modifying the hydrogen bonding motif of the hydrazone compound.

Transparency and AIE tunable supramolecular polymer hydrogel acts as TEA-HCl vapor controlled smart optical material

Stimuli-responsive optical materials attract lots of attention due to their broad applications. Herein, a novel smart stimuli-responsive supramolecular polymer was successfully constructed using a simple tripodal quaternary ammonium-based gelator (TH). The TH self-assembles into a supramolecular polymer hydrogel (TH-G) and shows aggregation-induced emission (AIE) properties. Interestingly, the transparency and fluorescence of the TH-G xerogel film (TH-GF) could be reversibly regulated by use of triethylamine (TEA) and hydrochloric acid (HCl) vapor. When alternately fumed with TEA and HCl vapor, the optical transmittance of the TH-GF was changed from 8.9% to 92.7%. Meanwhile, the fluorescence of the TH-G shows an "ON/OFF" switch. The reversible switching of the transparency and the fluorescence of the TH-GF is attributed to the assembly and disassembly of the supramolecular polymer TH-G. Based on these stimuli-response properties, the TH-GF could act as an optical material and shows potential applications as smart windows or fluorescent display material controlled by TEA and HCl vapor.

Porous amorphous powder form phase-selective organogelator for rapid recovery of leaked aromatics and spilled oils

Phase-selective organogelators (PSOGs) have drawn wide attention due to their potential applications in recovery of leaked aromatics and spilled oils. However, powder form PSOGs with fast gelling abilities and broad applicabilities are still limited. Herein, we developed three D-gluconic acetal-based gelators with different alkyl chains, all of which show excellent gel properties for hydrocarbon solvents. The spectroscopic and X-ray results revealed that the gel formation was the synergy of hydrogen bonding, π-π stacking and van der Waals forces. Surprisingly, the powder form gelator A with a cis double bond in the alkyl chain could instantly and selectively gel aromatic hydrocarbons, and also rapidly solidify crude oils with widely ranging viscosities from seawater at room temperature within minutes. Further research revealed that A powder exhibited porous amorphous morphology because the cis double bonds broke the crystalline chain-chain interdigitation between the assemblies. Therefore, the fast dispersion and recombination of fibers under the action of oil molecules lead to the fast room temperature gel process. Overall, a non-toxic and low-cost powder form PSOG with rapid room temperature phase selective gelation ability for a wide range of oils makes it promising for the emergency treatment of oil spill and aromatics leakage.

Removal of phenol from aqueous solution using acid-modified Pseudomonas putida-sepiolite/ZIF-8 bio-nanocomposites

The discharge of phenol, a harmful pollutant, in the environment poses a threat to human health. With the rapid urbanization and industrialization of the land, there is a pressing need to find new technologies and efficient adsorption materials to address phenol contamination. As a potential adsorbent candidate, sepiolite (SEP) has garnered much interest owing to its large specific surface area, and excellent adsorption performance and biocompatibility. Herein, nanocomposite CESEP/ZIF-8, consisting of zeolite imidazole framework (ZIF-8) and hydrochloric acid-modified SEP (CESEP), was prepared and examined toward the adsorption of phenol. Adsorption equilibrium was achieved within 150 min at initial phenol solution concentrations of 10 and 20 mg/L. However, complete removal was not achieved. Accordingly, biodegradation was introduced. Microorganism Pseudomonas putida was immobilized onto CESEP/ZIF-8, which afforded synergistic adsorption and biodegradation action. Phenol at solution concentrations of 10 and 20 mg/L was effectively removed within 13 and 24 h, respectively (as opposed to 21 and 36 h when phenol was removed in the presence of free Pseudomonas putida solely). The synergistic physical-biological treatment presented herein is expected to have great potential in the field of wastewater treatment.

Smart Materials for Environmental Remediation Based on Two-Component Gels: Room-Temperature-Phase-Selective Gelation for the Removal of Organic Pollutants Including Nitrobenzene/O-Dichlorobenzene, and Dye Molecules from the Wastewater

Novel two-component gel systems based on aliphatic acid-hydroxy/base interaction were developed as smart materials for environmental remediation. The G1-A16 gelator could be used directly as a powder form to selectively gel aromatic solvents (nitrobenzene and o-dichlorobenzene) from their mixtures with wastewater (containing 0.5 M sodium nitrate and 0.5 M sodium sulfate) via a simple shaking strategy at room temperature without employing co-solvents and a heating-cooling process. Meanwhile, the two-component gel system can efficiently remove the toxic dyes from the aqueous solution. The dominant factors that drive gelation in the case of the gelator and nitrobenzene or water have been studied using FT-IR, 1H NMR, and XRD. Overall, our research provides an efficient two-component approach for facilely tuning the properties of one-component gel for the realization of high-performance functionalities of gels. At the same time, our study demonstrates potential industrial application prospect in removing pollutants efficiently (such as aromatic solvents and toxic dye removal).