Phenolic Polymers Research Articles

Abatement of Aromatic Contaminants from Wastewater by a Heat/Persulfate Process Based on a Polymerization Mechanism.

A novel approach to the abatement of pollutants consisting of their conversion to separable solid polymers is explored by a heat/persulfate (PDS) process for the treatment of high-temperature wastewaters. During this process, a simultaneous decontamination and carbon recovery can be achieved with minimal use of PDS, which is significantly different from conventional degradation processes. The feasibility of this process is demonstrated by eight kinds of typical organic pollutants and by a real coking wastewater. For the treatment of the selected pollutants, 30.2-91.9% DOC abatement was achieved with 24.8-91.2% carbon recovery; meanwhile, only 5.2-47.0% of PDS was consumed compared to a conventional degradation process. For the treatment of a real coking wastewater, 71.0% DOC abatement was achieved with 66.0% carbon recovery. With phenol as a representative compound, our polymerization-based heat/PDS process is applicable in a wide pH range (3.5-9.0) with a carbon recovery of >87%. Both SO4•- and HO• can be initiators for polymerization, with different contribution ratios under various conditions. Phenol monomers are semioxidized to form phenolic radicals, which are polymerized via chain transfer or chain growth processes to form separable solid phenol polymers, benzenediol polymers, and cross-linked polymers.

Using phenolic polymers to control the size and morphology of calcium carbonate microparticles.

Calcium carbonate (CaCO3) is a naturally occurring mineral that occurs in biology and is used industrially. Due to its benign nature, CaCO3 microparticles have found use in the food and medical fields, where the specific size of the microparticles determine their functionality and potential applications. We demonstrate that phenolic polymers with different numbers of hydroxy groups can be used to control the diameter of CaCO3 microparticles in a range of 2-9 μm, and obtained particles were relatively uniform. The largest particles (∼9 μm in diameter) were obtained using poly(2,3,4,5-tetrahydroxystyrene) (P4HS), which showed the highest water solubility among the tested phenolic polymers. The polymer concentration and stirring speed influenced the size of microparticles, where the size of the obtained particles became smaller as the concentrations of phenolic polymers increased and as the stirring speed increased, both likely due to promoting the formation of a large number of individual crystal seeds by shielding seed-seed fusion and increasing the chances for precursor contact, respectively. The preparation time and temperature had a great influence on the morphology of the CaCO3 particles, where vaterite transforms into calcite over time. Specifically, aragonite crystals were observed at preparation temperature of 80 °C and vaterite particles with rough surfaces were obtained at 40 °C. Molecular weight and scale of reaction were also factors which affect the size and morphologies of CaCO3 particles. This research represents a facile method for producing relatively monodisperse CaCO3 microparticles with diameters that have previously proven difficult to access.

Tribological behaviour of phenolic formaldehyde polymer matrix composite reinforced with fly-ash and silicon carbide

Polymer composites offer engineers and homeowners a new material alternative. The efficiency boost caused success by adding tiny atoms to the origin has indicated extensive research into polymeric composites. Polymeric composite is moved apiece obvious possessions of silicon carbide particles and flee ruins. This composite material has many uses, for example, mechanical, automobile, sea, apparatuses and bundling. The wear behaviour of the composite material, that is intentional through wear testing, is examined afterwards it is typified utilizing a variety of pressure-to-pressure percentages. The most troublesome synthetic material was silicon carbide. It has Mohs severity grade of 9. Notwithstanding severity, has break logo that make bureaucracy very valuable in caustic wheels. Its extreme warm generated power, high temperature substance, depressed warm growth and resistance, form silicon carbide is important in the assembling of extreme heat blocks and added recalcitrant. It is likewise classification as a semiconductor because it has an energetic conductivity namely corresponding to that of insulating matters and metals.Considering this we projected for integrating silicon carbide and fly ruins be affiliated with Phenolic Formaldehyde sticky substance. The supported polymer composites are manufactured by including cut carefully with sharp instrument method in differing weight percentages in polymer, for instance, 8%, 12% and 16%. The Tribological features, for instance, wear is studied in accordance with the ASTM Standard.

Catalytic pyrolysis of enzymatic hydrolysis lignin by transition-metal modified HZSM-5/MCM-41 core–shell catalyst for the enhancement of monocyclic aromatic hydrocarbons

Enzymatic hydrolysis lignin (EHL) is produced in large quantities during the fermentation of lignocellulosic biomass to produce ethanol, resulting in environmental pollution and resource waste. HZSM-5/MCM-41 core–shell zeolites (H/M) loaded with transition metal Mn, Fe, Co, Ni, Cu, and Zn at different loading levels (2, 4, 6, 8, and 10 wt%) were prepared as catalysts. Py-GC/MS was employed to investigate their effects on the selectivity for and relative abundance of monocyclic aromatic hydrocarbons (MAHs) in the catalytic pyrolysis products of EHL. On this basis, bimetal-loaded H/M catalysts were constructed, namely Fe-Zn@H/M, Fe-Co@H/M, Fe-Ni@H/M, Co-Zn@H/M, Co-Ni@H/M, and Zn-Ni@H/M. Co-Ni@H/M increased the selectivity for and relative abundance of MAHs by 11.68% and 28.01%, respectively, compared with the H/M catalyst. Moreover, Co-Ni@H/M induced a further increase in the selectivity for and abundance of MAHs compared with the corresponding monometal-loaded catalysts. The characterization results indicated that bimetallic Co and Ni loading were uniformly dispersed on the catalyst surface and did not change the structure of the parent catalyst but affected the pore characteristics and acidic site distribution of the catalyst. Further analysis of the pyrolysis products suggested that bimetallic Co and Ni loading enhanced the dealkylation capacity of the catalyst for furans, aldehydes and phenol derivatives. Oligomerization, cyclization and aromatization of short alkyl chains were promoted in the MAHs by Co-Ni@H/M. Meanwhile, bimetallic Co and Ni loading inhibited the polymerization of phenols and other oxygen-containing compounds by promoting dehydration, decarboxylation and decarbonylation, which indirectly reduced the formation of coke.

Enhanced flocculation of aluminum oxide particles by lignin-based flocculants in dual polymer systems

Lignin is an abundant phenolic polymer produced vastly in pulping processes that could be further valorized. In this work, anionic (AKLs) and cationic (CKLs) lignin-based polymers were made by polymerizing kraft lignin (KL) with acrylic acid (AA) or [2-(methacryloyloxy) ethyl] trimethyl-ammonium chloride (METAC), respectively. In the polymerization reactions, various molar ratios of AA or METAC to KL were applied to produce AKLs and CKLs with different characteristics. The produced AKLs and CKLs were used in single and dual systems to flocculate aluminum oxide in suspension. To assess the interaction of these lignin-based polymers with the aluminum oxide particles; the zeta potential, adsorption, and flocculation of the colloidal systems were evaluated comprehensively. The flocculation performance of the lignin-derived polymers was compared with that of the homopolymers of AA and METAC (PAA and PMETAC) and commercially used flocculants. In single polymer systems, among the anionic synthesized polymers and homopolymers, KL-A4 (an AKL) was the best flocculant for the aluminum oxide suspensions owing to its largest molecular weight (330 × 103 g/mol) and highest charge density (−4.2 mmol/g). Remarkably, when KL-A4 and KL-C4 (the CKL with the highest molecular weight and charge density) were used subsequently in a dual polymer system, a larger adsorbed mass and a more viscous adlayer were formed than those of single polymer systems on the surface of aluminum oxide particles. The synergy between KL-A4 and KL-C4 was even stronger than that between homopolymers, which led to more significant adsorption on the aluminum oxide surface and, consequently, more efficient flocculation, producing larger (22 μm) and stronger flocs, regardless of the agitation intensity used in the systems.

Transcriptomic analysis of wound-healing in Solanum tuberosum (potato) tubers: Evidence for a stepwise induction of suberin-associated genes

Suberin deposition involves both phenolic and aliphatic polymer biosynthesis and deposition in the same tissue. Therefore, any consideration of exploiting suberin for crop enhancement (e.g., enhanced storage, soil borne disease resistance) requires knowledge of both phenolic and aliphatic component biosynthesis and their coordinated, temporal deposition. In the present study, we use a wound-healing potato tuber system to explore global transcriptome changes during the early stages of wound-healing. Wounding leads to initial and substantial transcriptional changes that follow distinctive temporal patterns – primary metabolic pathways were already functional, or up-regulated immediately, and maintained at levels that would allow for precursor carbon skeletons and energy to feed into downstream metabolic processes. Genes involved in pathways for phenolic production (i.e., the shikimate pathway and phenylpropanoid metabolism) were up-regulated early while those involved in aliphatic suberin production (i.e., fatty acid biosynthesis and modification) were transcribed later into the time course. The pattern of accumulation of genes associated with ABA biosynthesis and degradation steps support a role for ABA in regulating aliphatic suberin production. Evaluation of putative Casparian strip membrane-like genes pinpointed wound-responsive candidates that may mediate the suberin deposition process.

Different combinations of laccase paralogs nonredundantly control the amount and composition of lignin in specific cell types and cell wall layers in Arabidopsis.

Vascular plants reinforce the cell walls of the different xylem cell types with lignin phenolic polymers. Distinct lignin chemistries differ between each cell wall layer and each cell type to support their specific functions. Yet the mechanisms controlling the tight spatial localization of specific lignin chemistries remain unclear. Current hypotheses focus on control by monomer biosynthesis and/or export, while cell wall polymerization is viewed as random and nonlimiting. Here, we show that combinations of multiple individual laccases (LACs) are nonredundantly and specifically required to set the lignin chemistry in different cell types and their distinct cell wall layers. We dissected the roles of Arabidopsis thaliana LAC4, 5, 10, 12, and 17 by generating quadruple and quintuple loss-of-function mutants. Loss of these LACs in different combinations led to specific changes in lignin chemistry affecting both residue ring structures and/or aliphatic tails in specific cell types and cell wall layers. Moreover, we showed that LAC-mediated lignification has distinct functions in specific cell types, waterproofing fibers, and strengthening vessels. Altogether, we propose that the spatial control of lignin chemistry depends on different combinations of LACs with nonredundant activities immobilized in specific cell types and cell wall layers.

Unlocking the role of lignin for preparing the lignin-based wood adhesive: A review

Adhesives––the resins widely used in particleboards , oriented strength boards, and plywood––are traditionally produced from fossil-based polymers. Owing to the toxicity, environmental pollution, and non-renewable raw materials associated with these polymers, attempts to synthesize environmentally friendly and renewable adhesives from bio-based materials has attracted increasing attention. Lignin is an abundant natural and renewable phenolic polymer with multiple types of functional groups, such as hydroxyl, carboxyl, and aldehyde groups. This has drawn considerable attention to the exploitation of this resource based on these functional groups. Because of the advantages of lignin, continued research efforts have been focused on using lignin to partially or completely replace conventional raw materials for adhesives, such as phenol and melamine. In addition, lignin is also used with other biomass materials to produce formaldehyde-free biomass-based adhesives, such as lignin–furfural, lignin–soy protein, and lignin–tannin adhesives. Despite inspiring progress, the preparation of lignin-based adhesives with performances higher than that of fossil-based adhesives remains a serious challenge. This review summarizes the progress made in recent decades in research and commercial application of lignin-based adhesives for wood products, including lignin-based formaldehyde resins and lignin-based formaldehyde-free adhesives, and proposes perspectives on lignin-based adhesives. • Lignin is an abundant natural and renewable phenolic polymer. • This review summarizes the application of lignin in wood adhesives. • Details of lignin-based adhesives, properties and mechanism are discussed. • More research should be done regarding the chemical structure and curing mechanism. • Challenges and prospects are discussed.

HRP-conjugated thermoresponsive copolymer as a nanoreactor for aqueous polymerization of phenols

Enzymatic polymerization of phenols catalyzed by horseradish peroxidase (HRP) in aqueous solution has been regarded as a green strategy for the synthesis of phenolic polymers while the indispensable employment of additives makes the separation of the phenolic polymers extremely inconvenient and the recycling of HRP also remains great challenge. Here, an HRP-conjugated thermoresponsive copolymer P(DMAA-co-AA)-b-P(NIPAM-co-nBA)-HRP was delicately constructed as a nanoreactor for the polymerization of phenols, which proceeded efficiently in water with good regioselectivity (∼85%) and yields (∼87%) above the lower critical solution temperature (LCST, 33 °C). After completion of the polymerization, the reaction mixture was cooled below the LCST and the nanoreactor disassembled to be fully water-soluble, allowing the facile separation of the insoluble phenolic polymers from the thermoresponsive catalyst. The products were isolated in nearly pure form by simple centrifugation and the supernatant containing the polymer-supported enzyme could be reused for at least 10 cycles without obvious loss in catalytic activity by the combination of the warming/cooling procedures.

A Comprehensive Analysis of Physiologic and Hormone Basis for the Difference in Room-Temperature Storability between 'Shixia' and 'Luosanmu' Longan Fruits.

Although the effects of phytohormones (mainly salicylic acid) on the storability of longan fruit have been reported, the relationship between postharvest hormone variation and signal transduction and storability remains unexplored. The basis of physiology, biochemistry, hormone content and signalling for the storability difference at room-temperature between ‘Shixia’ and ‘Luosanmu’ longan fruit were examined. ‘Luosanmu’ longan exhibited faster pericarp browning, aril breakdown and rotting during storage. ‘Luosanmu’ pericarp exhibited higher malondialdehyde but faster decreased total phenolics, flavonoid, glutathione, vitamin C, catalase activity and gene expression. Higher H2O2 and malondialdehyde but lower glutathione, glutathione-reductase and peroxidase activities, while higher activities and gene expressions of polygalacturonase, β-galactosidase and cellulose, lower covalent-soluble pectin, cellulose and hemicellulose but higher water-soluble pectin were observed in ‘Luosanmu’ aril. Lower abscisic acid and methyl jasmonate but higher expressions of LOX2, JAZ and NPR1 in pericarp, while higher abscisic acid, methyl jasmonate and salicylic acid together with higher expressions of ABF, JAZ, NPR1 and PR-1 in ‘Luosanmu’ aril were observed. In conclusion, the imbalance between the accumulation and scavenging of active oxygen in ‘Luosanmu’ longan might induce faster lipid peroxidation and senescence-related hormone signalling and further the polymerization of phenolics in pericarp and polysaccharide degradation in aril.

Effect of biochar application rate on changes in soil labile organic carbon fractions and the association between bacterial community assembly and carbon metabolism with time

Biochar aging affects the stability of soil carbon. Analyzing the effect of biochar on soil organic carbon (SOC) forms and their relations with microbial community assembly and carbon metabolism with time is helpful for soil carbon sequestration (by adapting the farm management approach). Four treatments with no, low, medium, and high biochar application rates (0 %, 1 %, 2 %, and 4 % of the total dry weight of topsoil before winter wheat planting, abbreviated as control, LB, MB, and HB, respectively) were conducted in the field. The SOC and particulate organic carbon positively correlated with the biochar application rate. Biochar decreased readily oxidizable carbon (P < 0.05) after 8 months of application compared to the control; however, the difference disappeared with time. Biochar increased dissolved organic carbon (DOC) but had no effect on water- soluble organic carbon (WSOC); DOC and WSOC decreased with time. Furthermore, LB and HB stabilized the bacterial alpha diversities with time. Based on high-throughput sequencing, HB reduced the relative abundance of Actinobacteriota but increased that of Acidobacteria (P < 0.05) after 12 months of biochar application. Time-wise, the bacterial community assembly was determined by deterministic processes that were significantly affected by the available nitrogen, DOC, or WSOC. Compared with the control, biochar decreased bacterial links and improved bacterial metabolism of phenolic acids and polymers with time, as evidenced by Biolog EcoPlates. Structural equation modeling revealed that the contribution of bacterial assembly processes to carbon metabolism changed with time. Microbial carbon metabolism was most positively influenced by differences in the composition of bacterial specialists. These findings reinforced that changes in soil labile organic carbon were time-dependent but not necessarilty affected by the biochar application rate.

Recovery of Lignins with Potent Antioxidant Properties from Shells of Edible Nuts by a Green Ball Milling/Deep Eutectic Solvent (DES)-Based Protocol.

Lignins are phenolic polymers endowed with potent antioxidant properties that are finding increasing applications in a variety of fields. Consequently, there is a growing need for easily available and sustainable sources, as well as for green extraction methodologies of these compounds. Herein, a ball milling/deep eutectic solvent (DES)-based treatment is reported as an efficient strategy for the recovery of antioxidant lignins from the shells of edible nuts, namely chestnuts, hazelnuts, peanuts, pecan nuts, and pistachios. In particular, preliminarily ball-milled shells were treated with 1:2 mol/mol choline chloride:lactic acid at 120 °C for 24 h, and the extracted material was recovered in 19–27% w/w yields after precipitation by the addition of 0.01 M HCl. Extensive spectroscopic and chromatographic analysis allowed for confirmation that the main phenolic constituents present in the shell extracts were lignins, accompanied by small amounts (0.9% w/w) of ellagic acid, in the case of chestnut shells. The recovered samples exhibited very promising antioxidant properties, particularly in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay (EC50 values ranging from 0.03 to 0.19 mg/mL). These results open new perspectives for the valorization of nut shells as green sources of lignins for applications as antioxidants, e.g., in the biomedical, food, and/or cosmetic sector.

Methane Production by Facultative Anaerobic Wood-Rot Fungi via a New Halomethane-Dependent Pathway.

ABSTRACTThe greenhouse gas methane (CH4) is of pivotal importance for Earth’s climate system and as a human energy source. A significant fraction of this CH4 is produced by anaerobic Archaea. Here, we describe the first CH4 production by facultative anaerobic wood-rot fungi during growth on hydroxylated/carboxylated aromatic compounds, including lignin and lignite. The amount of CH4 produced by fungi is positively correlated with the amount of CH3Cl produced during the rapid growth period of the fungus. Biochemical, genetic, and stable isotopic tracer analyses reveal the existence of a novel halomethane-dependent fungal CH4 production pathway during the degradation of phenol and benzoic acid monomers and polymers and utilization of cyclic sugars. Even though this halomethane-dependent pathway may only play a side role in anaerobic fungal activity, it could represent a globally significant, previously overlooked source of biogenic CH4 in natural ecosystems.IMPORTANCE Here, we demonstrate that wood-rot fungi produce methane anaerobically without the involvement of methanogenic archaea via a new, halomethane-dependent pathway. These findings of an anaerobic fungal methane formation pathway open another avenue in methane research and will further assist with current efforts in the identification of the processes involved and their ecological implications.

Chemically Different but Often Mistaken Phenolic Polymers of Food Plants: Proanthocyanidins and Lignin in Seeds.

Flavonoid based proanthocyanidins and cinnamyl alcohol based lignins are chemically complex phenolic oligomers/polymers that are found in food plants. Although structurally very different, these two biopolymers are often not distinguished, for example, in the (quantitative) compositional analysis of cell walls and dietary fiber. Here, we analytically distinguish lignin and proanthocyanidins in dietary fiber samples by using degradative and nondegradative techniques and provide information about their occurrence, abundance, and structural characteristics in seeds of chokeberries, cranberries, raspberries, red currants, and grapes. These data revealed that the seeds of botanically diverse fruits largely differ in terms of their phenolic fiber polymers. The mostly hardened tissue of the seeds is not necessarily based on lignified cell walls. For example, red currant and chokeberry seeds almost exclusively contain proanthocyanidins, and raspberry seeds were clearly lignified (G-H-lignin) but did not contain proanthocyanidins. Our data also allows for estimating the bias of proanthocyanidins on different approaches of lignin analysis.

Horseradish Peroxidase–mediated Polymerization of Natural Phenol and Pyrrole for Coloration and Functionalization of Silk Fabrics

ABSTRACT In this study, we successfully polymerized natural phenol (gallic acid, ferulic acid) and pyrrole (Py) monomers by oxidative polymerization of horseradish peroxidase (HRP). Then, we successfully colored silk fabrics using these chemicals. We analyzed the polymerization mechanism of polyphenol and polypyrrole complexes in detail using UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS). In addition, we investigated the electrochemical activity, thermal properties and anti-UV activity of the colored silk fabrics. We found that the oxidative polymerization of phenol and Py on silk fibers under mild reaction conditions using HRP produced technically conductive silk fabrics that combine the superior chemical and physical properties of silk fabrics with superior levels of electrochemical activity and thermal stability. Upon analyzing the color depth of the fabrics, we found that silk fabrics treated with Py have a darker color than silk fabrics treated in the absence of Py. Additionally, the fabrics had slightly different levels of color fastness, but all were within the acceptable range. This technique expands the range of applications of natural phenols for textile dyeing and functionalization as well as providing new prospects for the enzymatically environmentally friendly production of natural functional fabric.

Novel Novolac Phenolic Polymeric Network of Chalcones: Synthesis, Characterization, and Thermal-Electrical Conductivity Investigation.

A series of novolac phenolic polymeric networks (NPPN) were prepared via an acid-catalyzed polycondensation reaction of formaldehyde with chalcones possessing a p-phenolic OH group. When p-hydroxybenzaldehyde was treated with formaldehyde under the same conditions, a phenolic polymer (PP) was obtained. The resulting polymers were isolated in excellent yields (83–98%). Isolated polymers (NPPN, PP) were characterized using FTIR, TGA, and XRD. The results obtained from the TGA revealed that all prepared phenolic polymers have high thermal stability at high temperatures and can act as thermosetting materials. XRD data analysis showed a high degree of amorphousness for all polymers (78.8–89.2%). The electrical conductivities and resistivities of all chalcone-based phenolic networks (NPPN) and p-hydroxybenzaldehyde polymer (PP) were also determined. The physical characteristics obtained from the I-V curve showed that the conductivity of phenolic polymers has a wide range from ultimately negligible values of 0.09 µS/cm up to 2.97 μS/cm. The degree of polarization of the conjugated system’s carbonyl group was attributed to high, low, or even no conductivity for all phenolic polymers since the electronic effects (inductive and mesomeric) could impact the polarization of the carbonyl group and, consequently, change the degree of the charge separation to show varied conductivity values.

Investigating the Relation between Skin Cell Wall Composition and Phenolic Extractability in Cabernet Sauvignon Wines

In this study, phenolic extractability of Cabernet Sauvignon grapes from two California regions (Sonoma County and Central Coast) and its relation with skin cell wall composition was investigated. Phenolic grape composition, wine phenolic content as well as berry and pomace cell wall composition of three sites per region were determined. Grape cell wall material (CWM) composition, and thus pomace CWM composition, was impacted by the growing region. The process of fermentation modified CWM composition, solubilizing some of the compounds such as pectin and polysaccharides making pomace CWM composition from different sites more similar in the case of Sonoma County and more different for the samples grown in the Central Coast. Growing region had a significant impact on grape phenolics, particularly on flavan−3-ols and polymeric phenols, whereas polymeric pigments and anthocyanin contents were more similar among samples. Wines made from Sonoma County grapes showed higher anthocyanin and polymeric phenol content when compared to wines made from Central Coast grapes. Comparing wine to grape phenolic composition suggests a large difference in extractability based on region. Of all the CWM components analyzed, only lignin and the amount of cell wall isolated were found to have a significant impact on phenolic extractability.

Synthesis of Polymer-Derived Carbon for Ibuprofen Removal from Simulated Wastewater

Ibuprofen is a nonsteroidal anti-inflammatory drug classified as one of the emerging contaminants from the pharmaceuticals group. Ibuprofen detected in the environment indicates that wastewater treatment facilities have a limited ability to remove this substance. Residual ibuprofen that accumulates continuously can harm ecosystems in the waters and indirectly affect human health. Adsorption using porous material is a method that can reduce the amount of ibuprofen in wastewater. This research synthesized porous carbon by pyrolysis of phenolic polymer. The resulting material was then characterized using an N2-sorption analyzer, SEM, and XRD. After being characterized, the material was used to adsorb ibuprofen at various concentrations. SEM characterization showed that carbon had voids or channels for adsorbing ibuprofen molecules. N2-sorption analyzer delivered that the polymer-derived carbon has a specific surface area of about ​​594 m2 g-1. Based on the adsorption test result, the porous carbon could adsorb the ibuprofen molecules in the simulated wastewater well and followed the Freundlich equilibrium model.

Thermal Control Using Far-Infrared Irradiation for Producing Deglycosylated Bioactive Compounds from Korean Ginseng Leaves.

Although ginseng leaf is a good source of health-beneficial phytochemicals, such as polyphenols and ginsenosides, few studies have focused on the variation in compounds and bioactivities during leaf thermal processing. The efficiency of far-infrared irradiation (FIR) between 160 °C and 200 °C on the deglycosylation of bioactive compounds in ginseng leaves was analyzed. FIR treatment significantly increased the total polyphenol content (TPC) and kaempferol production from panasenoside conversion. The highest content or conversion ratio was observed at 180 °C (FIR-180). Major ginsenoside contents gradually decreased as the FIR temperature increased, while minor ginsenoside contents significantly increased. FIR exhibited high efficiency to produce dehydrated minor ginsenosides, of which F4, Rg6, Rh4, Rk3, Rk1, and Rg5 increased to their highest levels at FIR-190, by 278-, 149-, 176-, 275-, 64-, and 81-fold, respectively. Moreover, significantly increased antioxidant activities were also observed in FIR-treated leaves, particularly FIR-180, mainly due to the breakage of phenolic polymers to release antioxidants. These results suggest that FIR treatment is a rapid and efficient processing method for producing various health-beneficial bioactive compounds from ginseng leaves. After 30 min of treatment without leaf burning, FIR-190 was the optimum temperature for producing minor ginsenosides, whereas FIR-180 was the optimum temperature for producing polyphenols and kaempferol. In addition, the results suggested that the antioxidant benefits of ginseng leaves are mainly due to polyphenols rather than ginsenosides.

New insights and advances on pyomelanin production: from microbial synthesis to applications.

Pyomelanin is a brown-black phenolic polymer and results from the oxidation of homogentisic acid (HGA) in the L-tyrosine pathway. As part of the research for natural and active ingredients issued from realistic bioprocesses, this work re-evaluates the HGA pigment and makes an updated inventory of its syntheses, microbial pathways, and properties, with tracks and recent advances for its large-scale production. The mechanism of the HGA polymerization is also well documented. In alkaptonuria, pyomelanin formation leads to connective tissue damage and arthritis, most probably due to the ROS issued from HGA oxidation. While UV radiation on human melanin may generate degradation products, pyomelanin is not photodegradable, is hyperthermostable, and has other properties better than L-Dopa melanin. This review aims to raise awareness about the potential of this pigment for various applications, not only for skin coloring and protection but also for other cells, materials, and as a promising (semi)conductor for bioelectronics and energy.