Phenolic Products Research Articles

Controlling C−OAryl Hydrogenolysis vs Aryl Hydrogenation in Lignin Model Depolymerization Using Ni‐, Rh‐ or Ni/Rh‐based Silica Catalysts

AbstractThis paper focuses on the hydrogenolysis of 2‐phenoxy‐1‐phenylethanone, modelling a pre‐oxidized form of lignin using five catalysts of similar metal content, prepared by impregnation of Ni(II), Rh(III) and both metals onto Aerosil‐380 in the presence of NH3, followed by a reduction step. The materials were characterized in the dried as‐synthesized state and after consecutive reductive and oxidative treatments, showing the great dispersion of the metal (oxide nanoparticles with sizes<2 nm). Working with 1 mol % of the reduced metal (500 °C) per substrate at 180 °C with isopropanol as H‐donor, the most active catalyst, but also the least selective towards phenol, was initially found to be the Ni‐based one. Under similar conditions, the lower capacity of the Rh‐based catalyst to induce H transfer from isopropanol favoured phenol formation but resulted in much slower C−OAr cleavage. Despite a very high dispersion of the two metals in the bimetallic catalysts, no synergy was found, suggesting that Ni would be segregated at the surface. Finally, the best phenol productivity could be reached by reducing the Ni‐based catalyst at 650 °C, which led to a more efficient cleavage of C−OAr bonds. In this way, it was possible to produce 8 times more phenol per hour.

Functional Fruit Trees from the Atlantic and Amazon Forests: Selection of Potential Chestnut Trees Rich in Antioxidants, Nutrients, and Fatty Acids.

The Amazon rainforest and the biodiversity hotspot of the Atlantic Forest are home to fruit trees that produce functional foods, which are still underutilized. The present study aimed to select potential functional nut donor trees from two Brazilian chestnuts, by evaluating the nutritional and antioxidant composition of the nuts and the fatty acid profile of the oil. The nutritional characteristics, antioxidants, oil fatty acid profile, and X-ray densitometry of the nuts were evaluated, as well as the characterization of leaf and soil nutrients for each parent tree. The nut oil was evaluated through Brix (%), mass (g), yield (%), and the fatty acid profile. For L. pisonis, the most nutritious nuts were produced by L. pisonis tree 4 (N > P > K > Mg > Ca > Zn > Fe) and L. pisonis tree 6 (P > Ca > Mg > Mn > Zn > Cu > Fe), and for the species L. lanceolata, L. lanceolata tree 6 (N > P > Ca > Mg > Zn > Fe > Cu) and L. lanceolata tree 2 (P > K > Mg > Zn > Cu). In L. pisonis, the highest production of anthocyanins, DPPH, total phenolics, and flavonoids was obtained from the nuts of L. pisonis tree 4 as well as for L. lanceolata, from L. lanceolata tree 1, except for flavonoids. The Brix of the oil from the nuts of both species showed no difference between the trees and the fatty acid profile with a similar amount between saturated (48-65%) and unsaturated (34-57%) fatty acids. Both species have nuts rich in nutrients and antioxidant compounds and can be considered unconventional functional foods. The data collected in the present study confirm that the nuts of these species can replace other foods as a source of selenium.

Performance improvement of metagenomic laccase immobilized on nanocellulose-reinforced hydrogel nanocomposites for enhanced delignification and detoxification

Immobilization enhances the potential of laccases to degrade lignocellulosic waste, thereby providing an efficient approach for delignification and detoxification. In this study, a comparative analysis of the activity of free and immobilized metagenome-derived laccase (PersiLac2) on nanocellulose (NC)-reinforced hydrogel nanocomposites was performed, and the effectiveness of immobilized laccase in delignification, particularly in relation to rice straw degradation and phenol production, was evaluated. After 1 h of incubation at 90 °C, the immobilized laccase retained 80% of its activity, exhibiting 1.6-fold higher retention than that of the free enzyme. At alkaline pH (8.0–9.0) the free enzyme demonstrated enzymatic activity of 55–65%, while this value was 59–73% for the immobilized form. Immobilization also facilitated easy recovery and reuse of PersiLac2. After 15 cycles, 76.64% of enzyme activity was preserved, highlighting the improved reusability and stability of the immobilized enzyme. Furthermore, leaching tests revealed that the hydrogel-enzyme conjugate maintained a strong connection, with only approximately 20% of the enzyme being leached after 240 min of incubation at 60 °C. This indicates a strong connection between the hydrogel and enzyme structure. Additionally, our study also employed SEM and FTIR analyses, demonstrating the superior performance of immobilized PersiLac2 compared to its free form in the treatment of rice straw. Furthermore, the immobilized enzyme reduced soluble phenols (77.45%) in the slurry of acid-pretreated rice straw. Overall, our findings highlight the potential of immobilizing PersiLac2 on hydrogel nanocomposites to improve enzyme stability, activity, and reusability. This study demonstrates a promising pathway for efficient delignification, phenolic compound removal, and enhanced biomass processing and waste management.

The APETALA2–MYBL2 module represses proanthocyanidin biosynthesis by affecting formation of the MBW complex in seeds of Arabidopsis thaliana

Proanthocyanidins (PAs) are the second most abundant plant phenolic natural products. PA biosynthesis is regulated by the well-documented MYB/bHLH/WD40 (MBW) complex, but how this complex itself is regulated remains ill defined. Here, in situ hybridization and β-glucuronidase staining show that APETALA2 (AP2), a well-defined regulator of flower and seed development, is strongly expressed in the seed coat endothelium, where PAs accumulate. AP2 negatively regulates PA content and expression levels of key PA pathway genes. AP2 activates MYBL2 transcription and interacts with MYBL2, a key suppressor of the PA pathway. AP2 exerts its function by directly binding to the AT-rich motifs near the promoter region of MYBL2. Molecular and biochemical analyses revealed that AP2 forms AP2–MYBL2–TT8/EGL3 complexes, disrupting the MBW complex and thereby repressing expression of ANR, TT12, TT19, and AHA10. Genetic analyses revealed that AP2 functions upstream of MYBL2, TT2, and TT8 in PA regulation. Our work reveals a new role of AP2 as a key regulator of PA biosynthesis in Arabidopsis. Overall, this study sheds new light on the comprehensive regulation network of PA biosynthesis as well as the dual regulatory roles of AP2 in seed development and accumulation of major secondary metabolites in Arabidopsis.

Structural changes and product distribution of typical Xinjiang coals and chars during pyrolysis

AbstractThis study used micro‐Raman spectroscopy, gas chromatography–mass spectrometry (GC–MS), and gas chromatography–flame ionization detector/thermal conductivity detector (GC–FID/TCD) to analyze the structure and pyrolysis reactions of nine typical coals and chars from Xinjiang. The study fitted 10 Gaussian bands of typical Xinjiang coal and investigated the changes in coal structure during coalification and pyrolysis. The results indicated that the reduction degree of CO structures in coal during coalification had a rough linear relationship with the Vdaf (dry ash‐free volatile matter) content. During coalification, the condensation of aromatic rings is accompanied by a continuous decrease of CO structures, while the contents of cross‐linking and substitution structures decrease persistently relative to the large aromatic ring structures. The influence of coal type on char yield for typical Xinjiang coal is within 15 wt.%; the influence on tar yield is within 8.5%, with a greater impact on the yield of alkanes and phenols in tar; the influence on CO yield in pyrolysis gas is within 6.3%. The relative content of large aromatic ring structures in coal is relatively stable during pyrolysis, while the relative content of small aromatic ring structures declines as coal transforms into char. The study inferred that small aromatic rings might decompose and transform into tar after pyrolysis reaction, which also resulted in a high selectivity of phenolic products in tar from most coal pyrolysis above 40%. This study revealed the structural changes and pyrolysis product distribution of nine typical coals and chars from Xinjiang, providing useful information for their utilization.

Influences of Reaction Temperature, Duration, and Catalysts on Hemicellulose Pyrolysis Products

Fast pyrolysis experiments were conducted on xylan (XY) using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) to explore influences of the reaction temperature, duration, and catalysts on product distributions from XY pyrolysis. The results show that temperature and duration can notably influence the classes and yields of compounds generated by the pyrolysis of hemicellulose. Pyrolysis at 500–600 °C for a duration of 5–20 s is conducive to improving the yields of condensable volatiles from hemicellulose pyrolysis. In all catalytic experiments, when taking HZSM-5 as the catalyst, alcohols (37.31%), carbohydrates (27.61%), and hydrocarbons (3.71%) have the highest contents while aldehydes (9.76%), ketones (2.20%), esters (0%), furans (0%), and N-compounds (4.09%) possess the lowest contents. MCM-41 promotes production of aldehydes (59.94%), acids (5.11%), ketones (6.92%), phenols (0.30%), ethers (0.61%), and N-compounds (18.70%) while inhibiting generation of alcohols (1.21%) and carbohydrates (3.79%). ZrO2 is conducive to increasing the content of furans (2.23%) while decreasing the content of acids (0.64%).

High-level phenol bioproduction by engineered Pichia pastoris in glycerol fed-batch fermentation using an efficient pertraction system

This study aimed to establish a high-level phenol bioproduction system from glycerol through metabolic engineering of the yeast Pichia pastoris (Komagataella phaffii). Introducing tyrosine phenol-lyase to P. pastoris led to a production of 59 mg/L of phenol in flask culture. By employing a strain of P. pastoris that overproduces tyrosine—a precursor to phenol—we achieved a phenol production of 1052 mg/L in glycerol fed-batch fermentation. However, phenol concentrations exceeding 1000 mg/L inhibited P. pastoris growth. A phenol pertraction system utilizing a hollow fiber membrane contactor and tributyrin as the organic solvent was developed to reduce phenol concentration in the culture medium. Integrating this system with glycerol fed-batch fermentation resulted in a 214 % increase in phenol titer (3304 mg/L) compared to glycerol fed-batch fermentation alone. These approaches offer a significant framework for the microbial production of chemicals and materials that are highly toxic to microorganisms.

Rice resistance against Bipolaris oryzae infection is mediated by lower foliar potassium concentration

AbstractBrown spot, caused by Bipolaris oryzae, is a very important disease of rice. This study investigated the effect of potassium (K) on rice resistance to brown spot. The working hypothesis tested was that higher foliar K concentration could allow plants to respond more efficiently against fungal infection. Plants were grown in nutrient solution amended with three K rates (0.5, 1.0 and 2.5 mM) and noninoculated or inoculated with B. oryzae. The photosynthetic performance of plants, activities of defence and antioxidant enzymes and the concentrations of reactive oxygen species, phenolics and lignin were determined. Foliar K concentration was significantly higher by 38% and 91% for plants supplied with 1.0 and 2.5 mM K, respectively, compared to plants supplied with 0.5 mM K. Brown spot severity was significantly higher (≥20%) for plants supplied with 1.0 and 2.5 mM K than those supplied with 0.5 mM K (≤15%). Higher brown spot severity for plants supplied with 2.5 mM K resulted in changes in the photosynthetic apparatus, reduced chlorophyll a + b and carotenoids concentrations, and higher production of hydrogen peroxide and superoxide anion radical. In contrast, higher activities of defence and antioxidant enzymes and more production of phenolics for plants supplied with 0.5 mM K helped them to cope with B. oryzae infection more efficiently. In conclusion, rice resistance against brown spot was achieved by keeping a lower foliar K concentration linked to more active defence reactions, a robust antioxidative system and less damage to the photosynthetic apparatus.

A DFT study on substituents, solvent, and temperature effect and mechanism of Diels-Alder reaction of hexafluoro-2-butyne with furan.

Furan and its derivatives constitute a vital class of heterocyclic chemistry used widely in organic synthesis via Diels-Alder reactions. As fluorine incorporation has been of great interest due to the limited possible pathways, the present study on [4 + 2] cycloaddition Diels-Alder reaction, between hexafluoro-2-butyne and 2-substituted (NH2, OCH3, OTMS, NHBoc) furans, uses the reaction as a likely route. The computational study revealed that that the reaction is feasible in all conditions and is most favorable for NH2 substituent in furan. The study of the effect of temperature has depicted that low temperature favors the formation of adducts, while the rise in temperature prefers ring opening to form 4-substituted-2,3-di(trifluoromethyl)phenol derivatives. The feasibility of a reaction has been determined by Gibbs energy change. The transition state study has been performed to find the activation energy, C-C single bond formation and global electron density transfer (GEDT) involved in the adduct formation. MEP plots have been used to understand the region of electrophilicity and nucleophilicity character. Furthermore, the mechanism for the formation of phenol products has been discussed. The decomposition of the NHBoc group at higher temperatures has been proved via a proposed mechanism and compared with experimental results. The reaction was theoretically investigated using B3LYP hybrid functional with 6-311 + G(d,p) basis sets, in gas phase and under different solvent conditions like water, acetonitrile, and THF. The transition state structures of the adduct were optimized at the lower basis set B3LYP/6-31 + G(d,p) as well as at the higher basis set B3LYP/6-311 + G(d,p) level. The changes in Gibbs energy (∆G) for the formation of products at different temperatures and in various solvents have been calculated at B3LYP/6-311 + G(d,p) level.

Flowsheets for hydroxyacetone–phenol binary mixture separation: The use of special distillation methods

Objectives. To study the possibility of hydroxyacetone–phenol binary mixture (a constituent of a mixture of phenol production by the cumene method) separation in flowsheets based on the use of distillation special methods. This is the addition of separating agents to increase the relative volatility of the components of the original mixture, and the variation of pressure in the columns.Methods. A computational simulation in Aspen Plus® was used as the research method. Mathematical modeling of the vapor–liquid equilibrium was carried out using a local compositions model Non-Random Two Liquid. The viability of the latter was confirmed by comparing experimental and calculated on phase equilibrium data, and azeotropic data. The average relative error does not exceed 3%.Results. The dependence of the composition and boiling point of the hydroxyacetone–phenol azeotrope on pressure was determined in a computational experiment (as the pressure increases, the azeotrope is enriched with phenol). The possibility of using a complex of columns operating under different pressures to separate the mixture was shown (the shift of the azeotrope is about 9%). The change in the relative volatility of components of the original mixture in the presence of a high(diethylene glycol) and a low-boiling (acetone) separating agent was investigated. Both solvents are selective agents used in extractive and re-extractive distillation processes. Three technological separation flowsheets containing two distillation columns were proposed.Conclusions. The study established the operation parameters of the columns (number of theoretical stages, feed stages of the original mixture and separating agent, and reflux ratio) and energy consumption (total heat supplied to the columns boiler) of three separation flowsheets ensuring the production of products of a given quality (not less than 0.99 mol fractions). The flowsheet with diethylene glycol is characterized by the lowest energy consumption. It is recommended that complexes of extractive and re-extractive distillation be further optimized. This enables the second product of cumulus production—acetone—to be involved in the technological cycle.

Structural changes of poplar lignin during the ternary deep eutectic solvent (DES) treatment and synergetic alkali-DES treatment

Expenditure isolation of lignin and the understanding of its structural variations during different isolation process is essential for lignin high-value utilization. A green DES consisted with choline chloride (ChCl), ethylene glycol (EG) and 4-chlorobenzene sulfonic acid (4-Cl-BSA) was proposed for rapid lignin separation from poplar in this study. About 97.01% of lignin and 87.41% of hemicellulose were removed while the cellulose preservation achieved 95.02% under 90 °C for 30 min using this DES with the molar ratio of 1:2:0.7 (ChCl: EG: 4-Cl-BSA). The percentage of β-O-4 linkages, molecular weight and associated sugar content of DES lignin declined steadily with the enhancement of treatment severity. Additionally, the pre-extraction of hemicellulose through alkali treatment on subsequent lignin separation and lignin structural variations was also elucidated. The results suggested that alkali pretreatment opened the channels of the cell wall and increased DES permeability to the material, enhancing the DES separation of lignin. It also promoted the cleavage of the β-O-4 and PB linkages during followed DES separation lignin, and reduced the molecular weight and thermal stability of isolated DES lignin. In addition, the integrated DES lignin displayed higher purity and S/G ratio compared to lignin obtained from direct DES treatment. The Py-GC/MS results indicated the obtained DES lignin was suitable for phenolic compounds production and the total phenolic compounds yield ranged from 41.56% to 62.42%. This study provides insight into lignin structural transformation during different pretreatment and guides for dismantling cell walls.

Unraveling lignin's structural features for catalytic oxidative depolymerization and enhanced renewable resource utilization

The effective utilization of lignin, a complex and abundant biopolymer in biomass, holds great potential for sustainable biomass conversion and the development of renewable resources. This study focuses on the catalytic oxidative transformation of lignin, aiming to unravel its structural features and their impact on product diversity. The significance of the content of β-O-4 linkages in lignin becomes evident as a crucial factor influencing the yield of phenolic monomer products, emphasizing its utmost importance. Additionally, the presence of S-type structural units in lignin positively influences its catalytic conversion efficiency, as evidenced by higher S/G ratios and increased degradation yields. However, the complex nature of lignin, influenced by growth environment and pretreatment methods, presents challenges for its efficient depolymerization and utilization. Therefore, a comprehensive understanding of lignin's structure is crucial for advancing its effective utilization and the development of renewable resources. This research elucidates the catalytic conversion mechanisms of lignin, providing practical implications for promoting the utilization of renewable resources in relevant fields.

UV-A and UV-B combined with photosynthetically active radiation change plant growth, antioxidant capacity and essential oil composition of Pelargonium graveolens

BackgroundThe different wavelengths of solar radiation incident on earth [herein: Photosynthetically Active Radiation (PAR) , Ultra Violet-A (UV-A) and Ultra Violet-B (UV-B)] and their spectral balance not only have an impact on plants’ growth, morphology and physiology, but also are important for the quality and quantity of plant secondary metabolites.Material and methodsIn an outdoor study we addressed the effects of PAR intensity and UV-A and UV-B on the growth, yield, phenolic and flavonoid content, antioxidant activity and essential oil composition of Pelargonium graveolens L’Hér. The experiment was performed with split plots in a randomized complete block design with three replications. During the growth, two PAR intensities (ambient PAR and reduced PAR) and four UV treatments (ambient UV, enhanced UV-A, enhanced UV-B and enhanced UVA + B) were applied.ResultsHigh PAR intensity decreased the length and width of leaf, the height of plant and fresh weight of aerial parts, and increased the dry weight of aerial parts. Enhanced UV-B irradiation was associated with reduced plant height, leaf expansion and fresh and dry weight of aerial parts. Interestingly, the negative effect of UV-B radiation on morphology and growth of plant was largely alleviated by high PAR intensity. The amount of total phenols and flavonoids, antioxidant activity and essential oil production of P. graveolens strongly increased with the increase of UV-B irradiation and PAR. On the other hand, UV-A radiation did not significantly influence total phenol and flavonoid content, antioxidant activity and essential oil composition. Moreover, the combination of high PAR intensity and UV-B led to further increases in total flavonoid content and antioxidant capacity. Both high PAR intensity and enhanced UV-B increased the percentage of geraniol in essential oil, leading to a slight reduction of citronellol/geraniol ratio which is a marker of quality for rose geranium essential oil.ConclusionsOverall, we conclude that UV-B irradiation was associated to reduction of plant growth and yield, while, the adverse effect of UV-B irradiation on the plant was mitigated by high PAR intensity. On the other hand, both high PAR and enhanced UV-B boosted the production of phenols, flavonoids and essential oil. Considering that the lower citronellol/geraniol ratio is the most important indicator for the economic value of rose geranium essential oil, reducing citronellol/geraniol ratio under enhanced UV-B radiation and/or high PAR is likely to be favorable.

Diverse biological activities and secondary metabolites profile of Penicillium brevicompactum HE19ct isolated from the high-Andean medicinal plant Perezia coerulescens

Endophytic fungi produced attractive primary and secondary metabolites for industries, pharmacology, and biotechnology. The bioactive potential of HE19ct, identified as Penicillium brevicompactum according to ITS-BenA-caM, was addressed. Antimicrobial and antioxidant activities and secondary metabolite contents using four culture media in Agar-plate (ApF) and Submerged (SmF) fermentation were evaluated. Some plant growth-promoting (PGP) traits and their related genes were tested. HE19ct exhibited antimicrobial activity against Staphylococcus aureus, Enterococcus faecalis, Candida albicans, C. tropicalis, Fusarium sp., Geotrichum candidum, and Alternaria sp. All cultures showed DPPH scavenging activity and phenolic compounds, where ethyl acetate extract of SmF with malt extract showed higher activity and SmF/ApF with potato-dextrose exhibited higher yield, respectively. HE19ct solubilized tricalcium-phosphate and produced siderophore, endoglucanase, proteinase, and amylase. It enhanced the alfalfa's germination at 15 °C, root development, and phenols production at 15 and 24 °C. Phenols, tannins, anthraquinones, triterpenoids/steroids, and alkaloids production were detected depending on culture media. Polyketide synthase type I gene (PksI), subtilisin-like protease prb 1 (Pbr), and siderophore D (sidD) were PCR-amplified. Finally, HE19CT could be a promising source of interesting bioactive compounds for pharmacology and agriculture mainly in extreme conditions, then metabolomic and functional genetic research must be performed to support their appropriate application.

Co-pyrolysis of PCB and cotton stalk: Towards enhanced phenol production and debromination of pyrolysis oil

Co-pyrolysis of PCB and cotton stalk: Towards enhanced phenol production and debromination of pyrolysis oil

Comparative study for the separation and depolymerization behavior of lignin from different separation methods

Due to its natural phenolic structure, lignin is the promising feed stock for the production of value-added phenolic monomers. However, the poor understanding of the relationship among separation methods, lignin structure and depolymerization behavior hinders the regulation of phenolic monomers production. In this work, lignin samples were separated by four methods (organic solvent, ionic liquids, deep eutectic solvents, acid-alcohol) using different strategies and their structure difference were characterized and verified by various methods (FTIR, NMR, nitrobenzene oxidation). It was found p-toluenesulfonic acid (PTS) and deep eutectic solvents (DES) were effectively solvents for lignin separation and for structure protection. Highest lignin separation of 99.42% (PTS) and recovery/purity of 92.93%/91.76% (DES) were obtained. The less condensed lignin also showed better performance on mono-phenols production (26.52%). Whereas the condensation C–C bonds formed during separation would hinder the depolymerization and lead to a lower phenolic monomers yield. The research results can provide guidance for the rational selection of lignin separation technology and subsequent depolymerization to produce phenolic monomers.

Tree seedling shade tolerance arises from interactions with microbes and is mediated by functional traits

Shade tolerance is a central concept in forest ecology and strongly influences forest community dynamics. However, the plant traits and conditions conferring shade tolerance are yet to be resolved. We propose that shade tolerance is shaped not only by responses to light but also by a species’ defense and recovery functional traits, soil microbial communities, and interactions of these factors with light availability. We conducted a greenhouse experiment for three temperate species in the genus Acer that vary in shade tolerance. We grew newly germinated seedlings in two light levels (2% and 30% sun) and controlled additions of microbial filtrates using a wet-sieving technique. Microbial filtrate treatments included: <20 µm, likely dominated by pathogenic microbes; 40-250 µm, containing arbuscular mycorrhizal fungi (AMF); combination, including both filtrate sizes; and sterilized combination. We monitored survival for nine weeks and measured fine root AMF colonization, hypocotyl phenolics, stem lignin, and stem+root nonstructural carbohydrates (NSC) at three-week intervals. We found that differences in seedling survival between low and high light only occurred when microbes were present. AMF colonization, phenolics, and NSC generally increased with light. Phenolics were greater with <20 µm microbial filtrate, suggesting that soil-borne pathogens may induce phenolic production; and NSC was greater with 40-250 µm filtrate, suggesting that mycorrhizal fungi may induce NSC production. Across species, microbe treatments, and light availability, survival increased as phenolics and NSC increased. Therefore, shade tolerance may be explained by interactions among soil-borne microbes, seedling traits, and light availability, providing a more mechanistic and trait-based explanation of shade tolerance and thus forest community dynamics.

Norlobaridone Inhibits Quorum Sensing-Dependent Biofilm Formation and Some Virulence Factors in Pseudomonas aeruginosa by Disrupting Its Transcriptional Activator Protein LasR Dimerization.

In the present study, norlobaridone (NBD) was isolated from Parmotrema and then evaluated as a new potent quorum sensing (QS) inhibitor against Pseudomonas aeruginosa biofilm development. This phenolic natural product was found to reduce P. aeruginosa biofilm formation (64.6% inhibition) and its related virulence factors, such as pyocyanin and rhamnolipids (% inhibition = 61.1% and 55%, respectively). In vitro assays inhibitory effects against a number of known LuxR-type receptors revealed that NBD was able to specifically block P. aeruginosa's LasR in a dose-dependent manner. Further molecular studies (e.g., sedimentation velocity and thermal shift assays) demonstrated that NBD destabilized LasR upon binding and damaged its functional quaternary structure (i.e., the functional dimeric form). The use of modelling and molecular dynamics (MD) simulations also allowed us to further understand its interaction with LasR, and how this can disrupt its dimeric form. Finally, our findings show that NBD is a powerful and specific LasR antagonist that should be widely employed as a chemical probe in QS of P. aeruginosa, providing new insights into LasR antagonism processes. The new discoveries shed light on the mysterious world of LuxR-type QS in this key opportunistic pathogen.

Targeted control of supporting pathways in paclitaxel biosynthesis with CRISPR-guided methylation.

Introduction: Plant cell culture biomanufacturing is rapidly becoming an effective strategy for production of high-value plant natural products, such as therapeutic proteins and small molecules, vaccine adjuvants, and nutraceuticals. Many of these plant natural products are synthesized from diverse molecular building blocks sourced from different metabolic pathways. Even so, engineering approaches for increasing plant natural product biosynthesis have typically focused on the core biosynthetic pathway rather than the supporting pathways. Methods: Here, we use both CRISPR-guided DNA methylation and chemical inhibitors to control flux through the phenylpropanoid pathway in Taxus chinensis, which contributes a phenylalanine derivative to the biosynthesis of paclitaxel (Taxol), a potent anticancer drug. To inhibit PAL, the first committed step in phenylpropanoid biosynthesis, we knocked down expression of PAL in Taxus chinensis plant cell cultures using a CRISPR-guided plant DNA methyltransferase (NtDRM). For chemical inhibition of downstream steps in the pathway, we treated Taxus chinensis plant cell cultures with piperonylic acid and caffeic acid, which inhibit the second and third committed steps in phenylpropanoid biosynthesis: cinnamate 4-hydroxylase (C4H) and 4-coumaroyl-CoA ligase (4CL), respectively. Results: Knockdown of PAL through CRISPR-guided DNA methylation resulted in a profound 25-fold increase in paclitaxel accumulation. Further, through the synergistic action of both chemical inhibitors and precursor feeding of exogenous phenylalanine, we achieve a 3.5-fold increase in paclitaxel biosynthesis and a similar reduction in production of total flavonoids and phenolics. We also observed perturbations to both activity and expression of PAL, illustrating the complex transcriptional co-regulation of these first three pathway steps. Discussion: These results highlight the importance of controlling the metabolic flux of supporting pathways in natural product biosynthesis and pioneers CRISPR-guided methylation as an effective method for metabolic engineering in plant cell cultures. Ultimately, this work demonstrates a powerful method for rewiring plant cell culture systems into next-generation chassis for production of societally valuable compounds.

Melatonin-induced development of adventitious roots, biosynthesis of secondary cell products and greener synthesis of silver nanoparticles for biological activities using Indigofera heterantha

Indigofera heterantha is a medicinal shrub of the family Fabaceae that naturally produces pharmaceutically important polyphenolics and at the verge of extinction due to ruthless exploitation. The adventitious roots provide bases for the conservation of endangered plants by decreasing pressure on their wild populations and help in the large-scale production of pharmacologically important secondary metabolites. The main objective of the current study was to establish a feasible protocol for adventitious roots and to investigate the effect of melatonin on the biosynthesis of biomass, secondary cell products, and greener synthesis of silver nanoparticles (AgNPs) for various biological activities. Melatonin is an important growth promoter and plays a key role in plant defense that can be used as elicitors for large-scale production of secondary metabolites. Different concentrations of melatonin revealed that 1.5 mg l−1 melatonin was effective for the biosynthesis of maximum biomass during log phases of growth kinetics. The same melatonin concentration enhanced total phenolics content (TPC; 68.28 mg/g-DW), total flavonoids content (TFC; 24.34 mg/g-DW), total phenolics production (TPP; 153.63 g l−1), total flavonoids production (TFP; 54.80 g l−1), antioxidant activity and total secondary metabolites in adventitious roots. The melatonin-treated roots (300 mM) were able to produce maximum biogenic AgNPs, characterized by UV–vis spectroscopy (UV), scanning electron microscope (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD) and were used for various biological activities. These NPs displayed maximum antimicrobial activities and further revealed that AgNPs and aqueous root extract displayed higher cytotoxic activities. The protocol developed here provides an alternative strategy for germplasm conservation and melatonin proved to be one of the best elicitors for different activities and has the potential of scaling up by various pharmaceutical industrial applications.