Chitosan Oligomers Research Articles

The correlation of molecule weight of chitosan oligomers with the corresponding viscosity and antibacterial activity

In order to explore the correlation between the viscosity of chitosan oligomers-acetic solution and its viscosity average molecular weight (Mv), and determine the Mv range with a strong bactericidal effect. A series of chitosan oligomers were obtained by degraded chitosan (728.5 kDa) with dilute acid and chitosan oligomer (101.5 kDa) was characterized by FT-IR, XRD, H NMR and C NMR. The bactericidal effect of chitosan oligomers with different Mv on E. coli, S. aureus and C. albicans was measured by plate counting method. And the bactericidal rate was taken as the evaluation indicator, the optimum conditions were determined by single-factor experiments. The result showed that the molecular structure of chitosan oligomers and original chitosan (728.5 kDa) were similar. The viscosity of the chitosan oligomers in acetic acid solution was positively correlated with the Mv, and the chitosan oligomers with the Mv of 52.5–145.0 kDa had a strong bactericidal performance. In addition, the bactericidal rate of chitosan oligomers on experimental strains was more than 90% when the concentration of 0.5 g/L (bacteria) and 1.0 g/L (fungi), pH6.0, incubation time of 30 min. Thus, chitosan oligomers had a potential application value when the Mv was in the range of 52.5–145.0 kDa.

Phytochemical Constituents and Antimicrobial Activity of Euphorbia serrata L. Extracts for Borago officinalis L. Crop Protection

The Euphorbia genus is the third-largest group of blooming plants, features a rich morphological variability, has a near-cosmopolitan distribution, and diverse medicinal uses. Nonetheless, phytochemical information about Euphorbia serrata L. extracts is not available. The objective of this research was to examine the constituents of the hydromethanolic extract of its aerial parts and propose valorization pathways. The results of gas chromatography-mass spectroscopy (GC−MS) demonstrated that 3-methylbutyl formate, quinic acid, N1-(4-hydroxybutyl)-N3-methylguanidine acetate, and 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one were the main phytocompounds, which have antimicrobial activity. Such activity was assayed against Pseudomonas cichorii, Botrytis cinerea, Fusarium oxysporum, and Sclerotinia sclerotiorum, four of the most destructive diseases of borage (Borago officinalis L.) crops, obtaining minimum inhibitory concentrations (MICs) of 750 and 1000 μg·mL−1 against the bacterium and the three fungal taxa, respectively, in in vitro tests. Conjugation of the extract with chitosan oligomers (COS) enhanced this activity, leading to MIC values of 187.5, 750, 500, and 500 μg·mL−1 for P. cichorii, B. cinerea, F. oxysporum, and S. sclerotiorum, respectively. Additional in vivo assays against two of the pathogens confirmed the protective action of the COS–E. serrata extract conjugate complexes on artificially inoculated plants at a dose of 375 and 1000 μg·mL−1 for P. cichorii and F. oxysporum, respectively. These findings suggest that this plant species can be a rich source of biorationals for prospective use in crop protection.

Chitosan oligomers (COS) trigger a coordinated biochemical response of lemongrass (Cymbopogon flexuosus) plants to palliate salinity-induced oxidative stress

Plant susceptibility to salt depends on several factors from its genetic makeup to modifiable physiological and biochemical status. We used lemongrass (Cymbopogon flexuosus) plants as a relevant medicinal and aromatic cash crop to assess the potential benefits of chitosan oligomers (COS) on plant growth and essential oil productivity during salinity stress (160 and 240 mM NaCl). Five foliar sprays of 120 mg L−1 of COS were applied weekly. Several aspects of photosynthesis, gas exchange, cellular defence, and essential oil productivity of lemongrass were traced. The obtained data indicated that 120 mg L−1 COS alleviated photosynthetic constraints and raised the enzymatic antioxidant defence including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities that minimised salt-induced oxidative damage. Further, stomatal conductance (gs) and photosynthetic CO2 assimilation (A) were improved to support overall plant development. The same treatment increased geraniol dehydrogenase (GeDH) activity and lemongrass essential oil production. COS-induced salt resilience suggests that COS could become a useful biotechnological tool in reclaiming saline soil for improved crop productivity, especially when such soil is unfit for leading food crops. Considering its additional economic value in the essential oil industry, we propose COS-treated lemongrass as an excellent alternative crop for saline lands.

Efficacy of fungoid chitosans from Aspergillus niger and Agaricus bisporus in controlling the oxidative browning of model white wines

The efficacy of two water-insoluble chitosans from Aspergillus niger and Agaricus bisporus, in controlling the browning of model white wine solutions was assessed and compared with respect to sulfite addition (70 mg/L). A water-soluble oligomeric preparation from Agaricus bisporus was also included to test the effect of solubility and reduced molecular weight on the antibrowning capability of the polysaccharide. Chitosans were added at 0.5 g/L and 1 g/L. Color development, iron oxidoreductive equilibrium and generation of phenolic intermediates were monitored. Results demonstrated a significant and comparable anti-browning efficacy of both insoluble formulations (up to 85% reduction in browning development with respect to control samples), which mainly acted by chelating iron (up to around 4.4 mg/g of chitosan) and shifting its oxidoreductive equilibrium toward the reduced form. Oligomeric chitosan was ineffective for this purpose as it completely lacked chelating activity, which it is proposed, depended on its negligible interaction with tartaric acid. Data on browning and oxidation-related phenolic intermediates also revealed that sulfite promotes browning once it is completely oxidized.Industrial relevance: Following its very recent European authorization as novel food, chitosan from Agaricus bisporus has been evaluated for the first time and compared in wine-like conditions with the already known water-insoluble chitosan from Aspergillus niger. A further novelty are the data on water-soluble chitosan preparations, not yet permitted in wine but potentially interesting due to the potentially higher specific surface once in solution. The results, apart from providing information on a recently introduced source for enological chitosan, can be useful to producers and winemakers in deciding among fungoid preparations aimed to control the browning of products.

Silene uniflora Extracts for Strawberry Postharvest Protection.

Halophytes are gaining considerable attention due to their applications in saline agriculture, phytoremediation, medicine, and secondary metabolite production. This study investigated the bioactive components present in Silene uniflora (sea campion) hydromethanolic extract, and their antimicrobial activity was evaluated both in vitro and ex situ against two strawberry phytopathogens, namely Botrytis cinerea (grey mold) and Colletotrichum nymphaeae (anthracnose fruit rot). The main identified phytochemicals were mome inositol, saturated fatty acid esters, and cyclotetracosane. In vitro tests demonstrated complete inhibition of the growth of B. cinerea and C. nymphaeae at extract concentrations of 1000 and 1500 μg·mL-1, respectively, with an activity comparable to that of fosetyl-Al and substantially higher than that of azoxystrobin. This activity was improved upon conjugation with chitosan oligomers (COS), yielding inhibition values of 750 and 1000 μg·mL-1. The COS-S. uniflora conjugate complexes were then tested as protective treatments for postharvest storage of strawberry fruit, resulting in high protection against artificially inoculated B. cinerea and C. nymphaeae at doses of 3750 and 5000 μg·mL-1, respectively. The reported results open the door to the valorization of this halophyte as a source of biorationals for strawberry protection.

Crude Enzyme Concentrate of Filamentous Fungus Hydrolyzed Chitosan to Obtain Oligomers of Different Sizes.

Chitosan is a non-cytotoxic polysaccharide that, upon hydrolysis, releases oligomers of different sizes that may have antioxidant, antimicrobial activity and the inhibition of cancer cell growth, among other applications. It is, therefore, a hydrolysis process with great biotechnological relevance. Thus, this study aims to use a crude enzyme concentrate (CEC) produced by a filamentous fungus to obtain oligomers with different molecular weights. The microorganism was cultivated in a liquid medium (modified Czapeck-with carboxymethylcellulose as enzyme inducer). The enzymes present in the CEC were identified by LC-MS/MS, with an emphasis on cellobiohydrolase (E.C 3.2.1.91). The fungus of the Aspergillus genus was identified by amplifying the ITS1-5.8S-ITS2 rDNA region and metaproteomic analysis, where the excreted enzymes were identified with sequence coverage greater than 84% to A. nidulans. Chitosan hydrolysis assays compared the CEC with the commercial enzyme (Celluclast 1.5 L®). The ability to reduce the initial molecular mass of chitosan by 47.80, 75.24, and 93.26% after 2.0, 5.0, and 24 h of reaction, respectively, was observed. FTIR analyses revealed lower absorbance of chitosan oligomers' spectral signals, and their crystallinity was reduced after 3 h of hydrolysis. Based on these results, we can conclude that the crude enzyme concentrate showed a significant technological potential for obtaining chitosan oligomers of different sizes.

Synthesis of a New Poly(ε-caprolactone)-g-Chitosan Amphiphilic Graft Copolymer with a "Reverse" Structure.

Hydrophilic chitosan (CHT) and hydrophobic polyε-caprolactone (PCL) are well-known biocompatible and biodegradable polymers that have many applications in the biomedical and pharmaceutical fields. But the mixtures of these two compounds are considered incompatible, which makes them not very interesting. To avoid this problem and to further extend the properties of these homopolymers, the synthesis of a new graft copolymer, the fully biodegradable amphiphilic poly(ε-caprolactone-g-chitosan) (PCL-g-CHT) is described, with an unusual "reverse" structure formed by a PCL backbone with CHT grafts, unlike the "classic" CHT-g-PCL structure with a CHT main chain and PCL grafts. This copolymer is prepared via a copper-catalyzed 1,3-dipolar Huisgen cycloaddition between propargylated PCL (PCL-yne) and a new azido-chitosan (CHT-N3 ). In order to obtain an amphiphilic copolymer regardless of the pH, chitosan oligomers, soluble at any pH, are prepared and used. The amphiphilic PCL-g-CHT copolymer spontaneously self-assembles in water into nanomicelles that may incorporate hydrophobic drugs to give novel drug delivery systems.

Facile synthesis of a new eco-friendly epoxy-modified oligomeric chitosan-based chrome-free tanning agent towards sustainable processing of functional leather

To reduce the contamination of Cr6+ and dyes from tannery wastewater, a chromium-free tanning agent with rich terminal epoxy groups (COS-GTE) was synthesized using oligomeric chitosan (COS) and glycerol triglycidyl ether (GTE). The structural characteristics and application performance of prepared COS–GTE were investigated by FTIR NMR, GPC, SEM, adsorption properties of fatliquor and dyes, and other analysis techniques. The application results indicated that the shrinkage temperature of finished leather tanned with COS–GTE can reach 83.5 °C. Compared with traditional tanning materials (F-90 and TWS), the finished leather had better mechanical properties (tear strength of 47.410 N/mm2) and yellowing resistance. Moreover, the natural skin modified with COS–GTE showed excellent antimicrobial properties against Escherichia coli, Staphylococcus aureus, Aspergillus flavus, and Aspergillus niger. Especially, the finished COS-GTE tanned leather had a high absorption rate of fatliquor (69.27 %) and dyes (X = 93.21 %), which is beneficial for reducing comprehensive wastewater pollution. The research revealed that the COS–GTE not only can be considered a new biomass material to solve the problem of chromium and dye contamination in the leather industry but also endows leathers with a unique antimicrobial function to extend product protection and service time.

Chitosan-Modified Polyethyleneimine Nanoparticles for Enhancing the Carboxylation Reaction and Plants' CO2 Uptake.

Increasing plants' photosynthetic efficiency is a major challenge that must be addressed in order to cover the food demands of the growing population in the changing climate. Photosynthesis is greatly limited at the initial carboxylation reaction, where CO2 is converted to the organic acid 3-PGA, catalyzed by the RuBisCO enzyme. RuBisCO has poor affinity for CO2, but also the CO2 concentration at the RuBisCO site is limited by the diffusion of atmospheric CO2 through the various leaf compartments to the reaction site. Beyond genetic engineering, nanotechnology can offer a materials-based approach for enhancing photosynthesis, and yet, it has mostly been explored for the light-dependent reactions. In this work, we developed polyethyleneimine-based nanoparticles for enhancing the carboxylation reaction. We demonstrate that the nanoparticles can capture CO2 in the form of bicarbonate and increase the CO2 that reacts with the RuBisCO enzyme, enhancing the 3-PGA production in in vitro assays by 20%. The nanoparticles can be introduced to the plant via leaf infiltration and, because of the functionalization with chitosan oligomers, they do not induce any toxic effect to the plant. In the leaves, the nanoparticles localize in the apoplastic space but also spontaneously reach the chloroplasts where photosynthetic activity takes place. Their CO2 loading-dependent fluorescence verifies that, in vivo, they maintain their ability to capture CO2 and can be therefore reloaded with atmospheric CO2 while in planta. Our results contribute to the development of a nanomaterials-based CO2-concentrating mechanism in plants that can potentially increase photosynthetic efficiency and overall plants' CO2 storage.

In Vitro Anti-HIV-1 Activity of Chitosan Oligomers N-Conjugated with Asparagine and Glutamine.

Chitosan oligomers (COS) are polysaccharides obtained by the hydrolyzation of chitosan. They are water-soluble, biodegradable, and have a wide range of beneficial properties for human health. Studies have shown that COS and its derivatives possess antitumor, antibacterial, antifungal, and antiviral activities. The goal of the current study was to investigate the anti-human immunodeficiency virus-1 (HIV-1) potential of amino acid-conjugated COS compared to COS itself. The HIV-1 inhibitory effects of asparagine-conjugated (COS-N) and glutamine-conjugated (COS-Q) COS were evaluated by their ability to protect C8166 CD4+ human T cell lines from HIV-1 infection and infection-mediated death. The results show that the presence of COS-N and COS-Q was able to prevent cells from HIV-1-induced lysis. Additionally, p24 viral protein production was observed to be suppressed in COS conjugate-treated cells compared to COS-treated and untreated groups. However, the protective effect of COS conjugates diminished by delayed treatment indicated an early stage inhibitory effect. COS-N and COS-Q did not show any inhibitory effect on the activities of HIV-1 reverse transcriptase and protease enzyme. The results suggest that COS-N and COS-Q possess an HIV-1 entry inhibition activity compared to COS and further studies to develop different peptide and amino acid conjugates containing N and Q amino acids might yield more effective compounds to battle HIV-1 infection.

The grapevine LysM receptor-like kinase VvLYK5-1 recognizes chitin oligomers through its association with VvLYK1-1.

The establishment of defense reactions to protect plants against pathogens requires the recognition of invasion patterns (IPs), mainly detected by plasma membrane-bound pattern recognition receptors (PRRs). Some IPs, also termed elicitors, are used in several biocontrol products that are gradually being developed to reduce the use of chemicals in agriculture. Chitin, the major component of fungal cell walls, as well as its deacetylated derivative, chitosan, are two elicitors known to activate plant defense responses. However, recognition of chitooligosaccharides (COS) in Vitis vinifera is still poorly understood, hampering the improvement and generalization of protection tools for this important crop. In contrast, COS perception in the model plant Arabidopsis thaliana is well described and mainly relies on a tripartite complex formed by the cell surface lysin motif receptor-like kinases (LysM-RLKs) AtLYK1/CERK1, AtLYK4 and AtLYK5, the latter having the strongest affinity for COS. In grapevine, COS perception has for the moment only been demonstrated to rely on two PRRs VvLYK1-1 and VvLYK1-2. Here, we investigated additional players by overexpressing in Arabidopsis the two putative AtLYK5 orthologs from grapevine, VvLYK5-1 and VvLYK5-2. Expression of VvLYK5-1 in the atlyk4/5 double mutant background restored COS sensitivity, such as chitin-induced MAPK activation, defense gene expression, callose deposition and conferred non-host resistance to grapevine downy mildew (Erysiphe necator). Protein-protein interaction studies conducted in planta revealed a chitin oligomer-triggered interaction between VvLYK5-1 and VvLYK1-1. Interestingly, our results also indicate that VvLYK5-1 mediates the perception of chitin but not chitosan oligomers showing a part of its specificity.

A Coating Based on Bioactive Compounds from Streptomyces spp. and Chitosan Oligomers to Control Botrytis cinerea Preserves the Quality and Improves the Shelf Life of Table Grapes.

Botrytis cinerea is the most harmful postharvest disease of table grapes. Among the strategies that can be envisaged for its control, the use of coatings based on natural products is particularly promising. The study presented herein focuses on the assessment of the antagonistic capacity of two Streptomyces species and their culture filtrates against B. cinerea. Firstly, the secondary metabolites were characterized by gas chromatography-mass spectrometry, with N1-(4-hydroxybutyl)-N3-methylguanidine acetate and 2R,3S-9-[1,3,4-trihydroxy-2-butoxymethyl]guanine acetate as the main compounds produced by S. lavendofoliae DSM 40217; and cyclo(leucyloprolyl) and cyclo(phenylalanylprolyl) as the most abundant chemical species for S. rochei DSM 41729. Subsequently, the capacity of S. lavendofoliae DSM 40217 and S. rochei DSM 41729 to inhibit the growth of the pathogen was tested in dual culture plate assays, finding 85-90% inhibition. In agar dilution tests, their culture filtrates resulted in effective concentration values (EC90) in the 246-3013 μg·mL-1 range. Upon the formation of conjugate complexes with chitosan oligomers (COS) to improve solubility and bioavailability, a synergistic behavior was observed, resulting in lower EC90 values, ranging from 201 to 953 μg·mL-1. Ex situ tests carried out on 'Timpson' and 'Red Globe' table grapes using the conjugate complexes as coatings were found to maintain the turgor of the grapes and delay the appearance of the pathogen by 10-15 days at concentrations in the 750-1000 µg·mL-1 range. Hence, the conjugate complexes of COS and the selected Streptomyces spp. culture filtrates may be put forward as promising protection treatments for the sustainable control of gray mold.

Understanding mucus modulation behavior of chitosan oligomers and dextran sulfate combining light scattering and calorimetric observations

This study reports the fundamental understanding of mucus-modulatory strategies combining charged biopolymers with distinct molecular weights and surface charges. Here, key biophysical evidence supports that low-molecular-weight (Mw) polycation chitosan oligosaccharides (COSs) and high-Mw polyanion dextran sulfate (DS) exhibit distinct thermodynamic signatures upon interaction with mucin (MUC), the main protein of mucus. While the COS → MUC microcalorimetric titrations released ~14 kcal/mol and ~60 kcal/mol, the DS → MUC titrations released ~1200 and ~1450 kcal/mol at pH of 4.5 and 6.8, respectively. The MPT-2 titrations of COS → MUC and DS → MUC indicated a greater zeta potential variation at pH = 4.5 (relative variation = 815 % and 351 %, respectively) than at pH = 6.8 (relative variation = 282 % and 136 %, respectively). Further, the resultant binary (COS-MUC) and ternary (COS-DS-MUC) complexes showed opposite behavior (aggregation and charge inversion events) according to the pH environment. Most importantly, the results indicate that electrostatics could not be the driving force that governs COS-MUC interactions. To account for this finding, we proposed a two-level abstraction model. Macro features emerge collectively from individual interactions occurring at the molecular level. Therefore, to understand the outcomes of mucus modulatory strategy based on charged biopolymers it is necessary to integrate both visions into the same picture.

Chitin and Chitosan Binding to the α-Chitin Crystal: A Molecular Dynamics Study.

Understanding the binding of chitosan oligomers to the surface of a chitin nanocrystal is important for improving the enzymatic deacetylation of chitin and for the design of chitin/chitosan composite films. Here, we study the binding of several chito-oligomers to the (100) surface of an α-chitin crystal using molecular dynamics (MD), steered MD, and umbrella sampling. The convergence of the free energy was carefully considered and yielded a binding energies of -12.5 and -2 kcal mol-1 for 6-monomer-long chitin and uncharged chitosan oligomers, respectively. We also found that the results for the umbrella sampling were consistent with the force profile from the steered MD and with classical MD simulations of the adsorption process. Our results give insight into the molecular-scale interactions, which can be helpful for the design of new chitin composite films. Furthermore, the free energy curves we present can be used to validate coarse-grained models for chitin and chitosan, which are necessary to study the self-assembly of chitin crystals due to the long time scale of the process.

Optimization of Chitosan Extraction Process from Rapana venosa Egg Capsules Waste Using Experimental Design.

New green and sustainable sources were chosen to obtain chitosan, an important material, with many applications in different fields. The present study is focused on egg capsules of Rapana venosa waste as raw material for chitosan oligomers. As previous studies revealed that chitosan extraction from this material takes place with a low yield, the present research aimed to optimize this step. A 22 experimental plan, with three replicates in the center, was proposed to investigate the influence of NaOH concentration and temperature on the yield extraction. After a primary analysis of the experimental data, a favorable temperature value was selected (90 °C) at which the total dissolution of the egg capsules was obtained. Then, at this temperature, the experimental plan was extended exploring the influence of the NaOH concentration on three levels (5, 6, and 7%) and the extraction duration on two levels (60 and 85 min). Based on all experimental data, a neural model was obtained and validated. The neural model was used to maximize the yield, applying Genetic Algorithm (GA) implemented in Matlab®. The resulting optimal solution is: NaOH concentration 6.47%, temperature 90 °C, duration 120 min, with a yield value of 7.05%.

Development of an azo functionalized oligomeric chitosan sensor for rapid visual, spectrophotometric and spectrofluorometric detection of KMnO4 up to micromolar concentrations.

A water-soluble azo functionalized oligomeric chitosan reagent (β-NAC) has been developed for the visual detection and quantification of KMnO4 at micromolar concentrations. The β-NAC sensor was also explored as a detection probe for the spectrophotometric and spectrofluorometric detection of several metal ions and anions. The synthesized reagent was characterized by TGA-DTA-DTG analysis, DLS studies, BET analysis, and spectral analysis. The β-NAC reagent produces conspicuous colours with different concentrations and different pH values of KMnO4 solution. This provides evidence for high selectivity in the visual detection of KMnO4 up to the micromolar level because of its interactions in the case of KMnO4 only. The colour of the β-NAC reagent after interacting with KMnO4 (10-3 M) changes from brown to blood red. Furthermore, the β-NAC sensor was employed for the spectrophotometric detection of KMnO4. The absorption spectrum of β-NAC shows a peak at 327 nm and on interacting with KMnO4, it shows a bathochromic shift to 331 nm. The intensity of the peak at 331 nm increases as the concentration of KMnO4 was increased from 1 μM to 0.01 M. The detection and quantification limits in the spectrophotometric detection of KMnO4 were found to be 4.55 μM and 15.17 μM, respectively. The results of pH studies show that there is a pH effect of the KMnO4 solution on KMnO4 detection. The stability of the complex was determined by investigating the effect of time on the absorption intensity. In the spectrofluorometric detection, the fluorescence intensity of β-NAC at the 427 nm emission maxima was decreased on adding KMnO4 solution. The fluorescence quenching increased on increasing the KMnO4 concentration from 1 μM to 0.008 M. The optimum pH for fluorescence quenching was found to be 8. The detection and quantification limits in the spectrofluorometric detection of KMnO4 were found to be 0.967 μM and 3.223 μM, respectively. The Stern-Volmer constant value was found to be 41 366.2 L mol-1, confirming the significant complexation between KMnO4 and the β-NAC reagent. Interference studies were conducted to analyse the effect of various metal ions and anions on KMnO4 detection. Electrochemical studies were also performed to analyse the mechanism of complex formation.

Multifunctional Nanocarriers Based on Chitosan Oligomers and Graphitic Carbon Nitride Assembly.

In this study, a graphitic carbon nitride and chitosan oligomers (g-C3N4−COS) nanocarrier assembly, which was obtained by cross-linking with methacrylic anhydride (MA), was synthesized and characterized. Its characterization was carried out using infrared spectroscopy, elemental and thermal analyses, and transmission electron microscopy. The new nanocarriers (NCs), with an average particle size of 85 nm in diameter and a 0.25 dispersity index, showed photocatalytic activity (associated with the g-C3N4 moiety), susceptibility to enzymatic degradation (due to the presence of the COS moiety), and high encapsulation and moderate-high release efficiencies (>95% and >74%, respectively). As a proof of concept, the visible-light-driven photocatalytic activity of the NCs was tested for rhodamine B degradation and the reduction of uranium(VI) to uranium(IV). Regarding the potential of the nanocarriers for the encapsulation and delivery of bioactive products for crop protection, NCs loaded with Rubia tinctorum extracts were investigated in vitro against three Vitis vinifera phytopathogens (viz. Neofusicoccum parvum, Diplodia seriata, and Xylophilus ampelinus), obtaining minimum inhibitory concentration values of 750, 250, and 187.5 µg·mL−1, respectively. Their antifungal activity was further tested in vivo as a pruning wound protection product in young ‘Tempranillo’ grapevine plants that were artificially infected with the two aforementioned species of the family Botryosphaeriaceae, finding a significant reduction of the necrosis lengths in the inner woody tissues. Therefore, g-C3N4-MA-COS NCs may be put forward as a multifunctional platform for environmental and agrochemical delivery applications.

Chitosan oligomer and monomer (COAMs) benefit and its application in innovative organic method for root rot disease treatment in durian crops

Thailand is the world’s largest exporter of durian accounted for 77.33 % of the world consumption. One of the most problem of durian tree is pathogens. Durian root rot disease cause by various species of phytophthora, Fusarium spp., and Lasiodiplodia pseudotheobromae are the most important disease that cause crop lost, limit of production and durian tree can be damaged to death. Farmers have applied various fungicide such as metalaxyl to control these pathogens but their side effects of may come with risks, such as serious hazards to farmers, consumers and the environment. Fungicide-resistant Phytophthora strains have been reported in many countries including tropical countries. Chitosan oligomer and monomer (COAMs) derived from shell shrimp and crap are biological organic substance theirs interesting biological properties are biocompatible, non-toxic and biodegradable. They are applied in agriculture due to their properties of immune stimulant, antimicrobial activity such as antifungal and antibacterial, plant growth regulator and fertilizer additive. COAMs have been tested with Colletotrichum gloeosporioides, the anthracnose pathogen. The result show more than 95 % of mycelial inhibition slightly better than carbendazim. Fungi pathogen also cultured from infected sample of durian crops and has been tested with COAMs. The IC50 also found and COAMs could inhibit the mycelial growth with IC50 of dilution 1/35 (v/v). This study have applied innovative organic method to treat root rot disease in durian crops. The method is application of COAMs with integrated microorganisms (IMO) consist of Trichoderma harzianum, Bacillus subtilis and few of soil benefit microorganisms. Durian crops in eastern area of Thailand which have problem of root rot disease have been selected. Phloem tissues look through digital microscope have considered as criteria of severity and improvement of disease. COAMs and IMO have applied and follow up 30 days after last treatment. The phloem tissues show cured and improvement significantly better than chemical fungicide. This study shows the effectiveness of the innovative method for root rot disease treatment in durian crops by application of COAMs and IMO found significant improvement compare to chemical fungicide.

Valorization of Quercus suber L. Bark as a Source of Phytochemicals with Antimicrobial Activity against Apple Tree Diseases.

Cork, an anatomic adaptation of the bark of Quercus suber L. through its suberization process, finds its main application in the production of bottle stoppers. Its processing results in a large waste stream of cork fragments, granulates, and dust, which may be susceptible to valorization. The work presented here explored the use of its extracts to inhibit the growth of phytopathogenic microorganisms associated with apple tree diseases. The in vitro antimicrobial activity of cork aqueous ammonia extract was assayed against four fungi, viz. Monilinia fructigena and M. laxa (brown rot), Neofussicoccum parvum (dieback), and Phytophthora cactorum (collar and root rot), and two bacteria, viz. Erwinia amylovora and Pseudomonas syringae pv. syringae, either alone or in combination with chitosan oligomers (COS). Effective concentration values of EC90 in the 675-3450 μg·mL-1 range, depending on the fungal pathogen, were obtained in growth inhibition tests, which were substantially improved for the conjugate complexes (340-801 μg·mL-1) as a result of strong synergism with COS. Similar enhanced behavior was also observed in antibacterial activity assays, with MIC values of 375 and 750 μg·mL-1 for the conjugate complexes against P. syringae pv. syringae and E. amylovora, respectively. This in vitro inhibitory activity was substantially higher than those exhibited by azoxystrobin and fosetyl-Al, which were tested for comparison purposes, and stood out among those reported for other natural compounds in the literature. The observed antimicrobial activity may be mainly attributed to the presence of glycerin and vanillic acid, identified by gas chromatography-mass spectroscopy. In the first step towards in-field application, the COS-Q. suber bark extract conjugate complex was further tested ex situ against P. cactorum on artificially inoculated excised stems of the 'Garnem' almond rootstock, achieving high protection at a dose of 3750 μg·mL-1. These results suggest that cork industrial leftovers may, thus, be a promising source of bioactive compounds for integrated pest management.

"CHITOSAN OLIGOMERS – SYNTHESIS, CHARACTERIZATION AND PROPERTIES "

The paper presents the synthesis of chitosan oligomers with different polymerization degrees (PD) by chitosan depolymerization in the presence of nitrous acid, aiming to study the correlation between their polymerization degree and their properties. Seven oligomers were synthesized and purified. The oligomers were characterized from the structural point of view by FTIR, NMR and UV-Vis spectroscopy, revealing the formation of shorter chains with an ending unit of 2.5-D-anhydromannofuranose. The morphology evaluation at micro and nano levels by SEM and AFM revealed the granular morphology of the oligomer films, while WXRD and POM demonstrated their higher degree of ordering, in comparison with the parent chitosan. The antimicrobial tests showed the potential of the synthesized compounds to be used for biomedical purposes, the oligomers presenting antifungal activity, which increased with the decrease in their polymerization degree, especially against Aspergillus niger.