Inhibition Of Spore Germination Research Articles

<i>In vitro</i> assessment of the efficacy of three essential oils of aromatic plants against <i>Magnaporthe oryzae</i> B.C. Couch, a rice blast pathogen in Burkina Faso

Blast, caused by Magnaporthe oryzae B.C.Couch, is the main fungal disease in the rice fields in Burkina Faso. Three pure essential oils at different concentrations of Cymbopogon schoenanthus, Ocimum americanum and Lippia multiflora, and four of their combinations were tested in vitro to evaluate their inhibition properties on mycelial growth, sporulation, and spore germination of M. oryzae. The contact method and the fumigation method were used for the different tests at doses of 0.05 μl/ml, 0.1 μl/ml, 0.3 μl/ml, 0.6 μl/ml, 0.9 μl/ml, 1.2 μl/ml, 1.5 μl/ml, 1.8 μl/ml, 2.1 μl/ml and 2.4 μl/ml. Two chemical fungicides, mancozeb and azoxystrobin and an absolute control were used in the trials. The results showed that the pure essential oil of L. multiflora and its combination with that of C. schoenanthus presented the most effective minimum doses of inhibition in the contact and fumigation method. These doses ranged from 0.1 μl/ml to 0.3 μl/ml for 100% inhibition of radial growth, sporulation, and spore germination of Magnaporthe oryzae. Mancozeb inhibited 100% of all parameters evaluated, while azoxystrobin was ineffective. The essential oil of L. multiflora and its combination with that of C. schoenanthus can be tested in a real environment to control rice blast.

Evaluation of some bioactive compounds of <i>Azadirachta indica</i> extracts and its application as safe fungicide against different plant pathogenic fungi

Extracts of leaves, seeds and twigs of Azadirachta indica was carried out using Soxhlet extraction technique. These extracts were subjected to percent yield, in vitro phytochemical screening and antifungal activities (minimum fungicidal concentration (MFC), minimum inhibitory concentration (MIC), zone of inhibition and spore germination assay) against plant pathogenic fungi Cladosporium fulvum, Colletotrichum coccodes, Fusarium oxysporum and Rhizoctonia solani. The Soxhlet extractive solvents were methanol, ethanol, chloroform, ethyl acetate and n–hexane. The maximum extractive yield were calculated in ethanol leaves (26±1.5%), methanol leaves (22±01%), n–hexane seeds (32±0.8%) and ethanol seeds (24±01%), while twigs calculated minimum extractive yield. The phytochemicals screening findings confirmed the occurrence of terpenoids, phenols, flavonoids, glycosides, alkaloids, tannins and saponins. The antifungal activities observed that leaves and seeds extracts of neem might cause the inhibition of mycelium and spore germination of tested fungi, though the antifungal activities rate of under study fungal strains diverse with dissimilar concentration and nature of extracts. However the entire concentrations of extract and crude extract especially the methanol and ethanol extracts of neem seeds and leaves reduce the plant pathogenic fungi growth at noteworthy rate. It was concluded from our results that neem leaves and seeds extracts were effectual as antifungal agents against the entire under study fungal strains however the most sensitive fungi were Rhizoctonia solani and Fusarium oxysporum. The findings acquired from this study revealed that chemical constituents from neem seeds and leaves may be formulated as latent agrochemical fungicides.

Expression of a mycoparasite protease in plant petals suppresses the petal-mediated infection by necrotrophic pathogens

Sclerotinia sclerotiorum and Botrytis cinerea are necrotrophic plant-pathogenic fungi, causing substantial economic losses on many crops. So far, resistant cultivars against these pathogens are unavailable in most crops. Here, we show that the serine protease CmSp1 of Coniothyrium minitans, a well-characterized mycoparasite of S. sclerotiorum, contributed to suppressing the petal-mediated infection by S. sclerotiorum in rapeseed. Application of recombinant CmSp1 proteins facilitates the bulk degradation of S. sclerotiorum proteins and inhibits spore germination and hyphal growth of S. sclerotiorum and B. cinerea, thereby preventing the development of both diseases. Stable transgenic rapeseed plants with tissue-specific expression of CmSp1 in flower petals inhibit the petal-mediated infection by both S. sclerotiorum and B. cinerea, and resulting transgenic plants have no adverse effect on other agronomic traits. Thus, our findings provide a novel mechanism by which a mycoparasite inhibits fungal pathogens and an environmentally friendly disease management strategy.

Bioactive molecular family construction: Design, optimization and antifungal mechanism study of novel 2-phenylglycine derivatives

With the widespread use of fungicides, some problems have also gradually emerged, such as resistance, toxicity and residues. Therefore, to develop novel antifungal pesticides with unique structures, safety and high efficiency, a series of 2-phenylglycine derivatives were designed and synthesized. The bioactivity results revealed good antifungal activity of compound III11 and boscalid against Nigrospora oryzae, and they both effectively inhibited spore germination with EC50 values of 17.3 and 3.1 μg/mL, respectively. An antifungal mechanism study showed that both III11 and boscalid significantly increased the content of nucleic acids, proteins and MDA, which indicated that they could destroy the integrity of the mycelial cell membrane, thus affecting the normal growth of mycelia. Molecular docking results revealed that III11 bound with some amino acid residues (SER-39, ARG-14 and ARG-43) of succinate dehydrogenase (SDH) through a unique mode involving hydrogen bonds, different from the binding mode of boscalid. Further investigation demonstrated that III11 exhibited moderate inhibitory activity against SDH (IC50 = 54.5 μg/mL), weaker than that of boscalid (IC50 = 10.7 μg/mL). The results provided sufficient support for the optimization and derivatization of 2-phenylglycine derivatives, which could be further developed and designed as potential fungicides.

Bioinformatic analysis of the ABC transporter protein family and their function in Penicillium digitatum

ATP-binding cassette transporter (ABC transporter) has prominent effects on the normal growth, development, substance transport and drug detoxification of organisms. However, the function of most of the ABC family members in filamentous fungi remains unknown. In the present research, 171 ABCs were identified from fruit postharvest pathogenic Penicillium spp. fungi including P. digitatum, P. expansum and P. italicum, of which 45 were from P. digitatum. Bioinformatics analysis showed that all 45 PdABCs had ABC_tran domain, belonging to seven subfamilies and containing 1–12 introns, distributed on six chromosomes of P. digitatum. The transcriptome data of spore germination, infection and sodium dehydroacetate (SD) inhibition showed that 43 PdABCs were detected as expressed in at least one stage, 6 PdABCs were all significantly differenially expressed during spore germination, infection or SD repression, five, eight and six PdABCs were significantly differentially expressed at the spore germination, infection and SD repression stages, respectively. RT-qPCR experiments further validated these six co-differentially expressed PdABCs. Cis-acting element (CAE) analysis showed that C2H2, C6 and Heat shock factors family-specific binding elements were highly present in their promoters, and the interaction regulatory network analysis indicated that there were interactions between PdABCs and PdABCs, major facilitator superfamily (MFS) transporter proteins, cytochrome P450 proteins, TFs (PdRING1、PdHeat1、PdbZIP1、PdzincC6). This study contributes to the screening of key ABCs and provides foundations for further investigation into the function of PdABCs and the creation of novel antifungal drugs to combat citrus green mold.

Understanding Environmental and Physiological Factors Affecting the Biology of Diaporthe ilicicola, the Fungus Causing Latent Fruit Rot in Winterberry.

Fruit rot in winterberry is associated with a complex of fungal pathogens. Among them, Diaporthe ilicicola plays a unique role by infecting flowers at bloom, resulting in symptom development in mature fruit. This research aimed to identify at what stage of maturation Ilex fruit can develop disease symptoms and correlate changes in fruit physiology (sugar and phenolic content) and environment (temperature and light intensity) with disease incidence. Correlation data informed in vitro studies testing the ability of putative factors to alter growth of D. ilicicola and select opportunistic fungi within the fruit rot complex: Alternaria alternata, Colletotrichum fioriniae, and Epicoccum nigrum. Results indicated that Ilex fruit do not develop symptoms until 81 to 108 days after inoculation. Temperature and fruit phenolic content were negatively correlated with disease incidence, while fruit sugar concentration and light intensity were positively correlated. In vitro assays revealed that sugar concentration had no effect on the growth of D. ilicicola, but increased light intensity increased hyphal growth and pycnidium formation. Additionally, phenolics extracted from fruit inhibited spore germination in A. alternata, induced secondary conidiation in C. fioriniae, and late season phenolic extracts increased hyphal melanization and pycnidial formation in D. ilicicola. Finally, drops in field temperatures, when replicated in vitro, resulted in a decrease in hyphal growth and spore germination for all fungi. These results suggest that changes in Ilex fruit phenolics during maturation and the increased exposure to light following defoliation may play a role in symptom development by altering D. ilicicola growth within the fruit.

Postharvest mycobial contaminants of white button mushroom (Agaricus bisporus) and their management using plant essential oils

Being highly perishable, mushrooms’ quality and shelf life is affected by various factors during postharvest conditions, among which fungal contamination is the main cause. The goal of this study is to identify and manage fungal contaminants present in mushrooms during postharvest conditions. A total of 23 fungi were isolated as contaminants from the samples of Agaricus bisporus collected from three major vegetable markets in Kathmandu city, Nepal. Aspergillus niger, Aspergillus flavus, and Rhizopus stolonifer were found to be the most frequent fungal contaminants. These were treated with various concentrations of essential oils (EOs) of Cinnamomum tamala, Mentha spicata, Zanthoxylum armatum, and Eucalyptus citriodora using poisoned food technique. Significant (p<0.05) inhibition of mycelial growth and spore germination was found in all testedfungi by all EOs. A strong inhibitory action of M. spicata oil was recorded against A. flavus and R. stolonifer while, A. niger was best controlled by C. tamala oil at the concentration of 20 µl/ml. These results suggest that EOs of three tested plants could be a good alternative to control fungal contaminants and extend the shelf life of Agaricus bisporus in postharvest conditions.

Natural Product Aloesin Significantly Inhibits Spore Germination and Appressorium Formation in Magnaporthe oryzae.

This study aims to determine the effects of the natural product aloesin against Magnaporthe oryzae. The results exposed that aloesin had a high inhibitory effect on appressorium formation (the EC50 value was 175.26 μg/mL). Microscopic examination revealed that 92.30 ± 4.26% of M. oryzae spores could be broken down by 625.00 μg/mL of aloesin, and the formation rate of appressoria was 4.74 ± 1.00% after 12 h. M. oryzae mycelial growth was weaker than that on the control. The enzyme activity analysis results indicated that aloesin inhibited the activities of polyketolase (PKS), laccase (LAC), and chain-shortening catalytic enzyme (Aayg1), which are key enzymes in melanin synthesis. The inhibition rate by aloesin of PKS, LAC, and Aayg1 activity was 32.51%, 33.04%, and 43.38%, respectively. The proteomic analysis showed that actin expression was downregulated at 175.62 μg/mL of aloesin, which could reduce actin bundle formation and prevent the polar growth of hyphae in M. oryzae. This is the first report showing that aloesin effectively inhibits conidia morphology and appressorium formation in M. oryzae.

Development of konjac glucomannan based Syringa essential oil film and its fragmented form for quality maintenance of citrus fruits

Citrus fruits have suffered serious losses in postharvest storage and transportation. A novel approach, fragmented konjac glucomannan-based Syringa essential oil (KSE) films, was used to maintain the quality of citrus fruits in storage. The KSE film was successfully prepared by using the encapsulating method via coacervation, with an encapsulation efficiency of 18.3% and loading capacity of 11.4%. GC–MS showed that eugenol, caryophyllene, and humulene were the main constituents of Syringa EO. SEM showed that EO drops or volatiles distributed in the KGM molecular matrix produced a concave structure during film formation. FTIR indicated no interaction or modification between KGM and Syringa EO, and EO was successfully encapsulated into the KGM films. The fragmented KSE films showed significant antifungal activity against Penicillium italicum, Penicillium digitatum, and Geotrichum citri-aurantii, inhibiting spore germination and mycelium elongation, resulting in suspected indentation, plasmolysis, and vacuolization. In storage, the fragmented KSE film packed in a non-woven bag apparently maintained the quality of citrus fruits, including sustaining fruit firmness and reducing vitamin C (VC), total soluble solids (TSS), and titratable acid (TA) loss. One of the modes of action for the quality maintenance of citrus fruits might be induced systemic resistance. This study might convey stronger impact in postharvest by newly developed packaging materials.

Assessment of the Fungicidal and Nematicidal Potential of Reichardia tingitana (L.) Roth on Phytopathogenic Fungi and Plant Nematode

The primary concern was the removal of numerous soil fumigants and nematicides due to their potential risks to human and environmental safety. Fungal pathogens can cause serious diseases in humans and animals. Among these, root-knot nematodes such as Meloidogyne incognita and Tylenchulus semipenetrans pose a significant threat, leading to substantial damage and yield reduction in various economically important plants. Therefore, this study aimed to assess the fungicidal and nematicidal activities of the ethanol extract (EE) and lupeol (L), the major isolates from the aerial parts of Reichardia tingitana L. Roth (Asteraceae), against Aspergillus flavus and plant-parasitic nematodes. Antifungal actions of EE (10-120 ppm) and L (23.4-281.2 µM) were evaluated through in vitro and in vivo growth assays, spore germination inhibition assays, and the efficacy of inhibiting pod and kernel infection. Nematicidal activity of EE and L was tested by preparing cultures containing egg masses of nematode species M. incognita from infected eggplants and T. semipenetrans from infected citrus roots, using concentrations of 2.5, 5, 10, 20, 40, 80, and 120 ppm. Results showed that R. tingitana (EE) and (L) exhibited nematostatic or nematicidal effects on nematode viability, egg hatch in vitro, and development and reproduction in vivo. Lupeol was particularly effective in inhibiting the colonization of A. flavus in peanuts. EE and L demonstrated high toxicity against nematodes in laboratory exposure and were effective in controlling nematode infestation in eggplant roots for 45 days. Improvement in plant growth parameters, including shoot and root length and weights, varied and was proportional to the doses of EE and L treatments. The antifungal and bio-nematicide effects of the ethanol extract from the aerial parts of R. tingitana were superior to those of lupeol, which could be attributed to the synergistic effect of phytochemicals in the ethanol extract. Both EE and L have potential applications as antifungal and bio-nematicide agents.

Synthesis and Antiphytopathogenic Activity of Novel Oxazolidine-2,4-diones Bearing Phenoxypyridine Moiety.

In the present study, we conducted optimization of pyramoxadone and synthesized a series of novel oxazolidinediones. Antifungal assays showed that these compounds exhibited moderate to excellent antifungal activity against various pathogens. Further SAR analysis revealed that the introduction of substituents to the benzene ring of the phenoxy group or the inclusion of bulky groups, such as tert-butyl, on the aniline moiety, had a detrimental effect on the activity. However, the inclusion of fluorine atoms in the aniline moiety significantly enhanced the antifungal efficacy. Notably, compound 2-4 displayed significantly higher activity compared to both pyramoxadone and famoxadone against R. solani, B. cinerea, S. sclerotiorum, and P. oryzae, where it demonstrated EC50 values of 1.78, 2.47, 2.33, and 2.23 μg/mL, respectively. Furthermore, compound 2-4 exhibited potent protective and curative effects against the tomato gray mold in vivo. A mechanistic investigation revealed that compound 2-4 significantly impacted the mycelial morphology, inhibited spore germination, and impeded mycelial respiration, ultimately leading to the inhibition of pathogenic fungus growth. These findings indicate that compound 2-4 has the potential to serve as a cyt bc1 inhibitor and should be further investigated for development.

Actividad antifúngica in vitro de extractos de ramas/hojas de arándano y semilla de palta contra Botrytis sp.

Currently, the search for eco-friendly products has become more intensive, guiding the agro-industry towards more sustainable practices. Obtaining bioactive compounds with antifungal activity represents a viable source of fungicides for postharvest use, since up to now there is still a high demand for chemical fungicides in the industry. The effect of two aqueous extracts of acetone origin obtained from blueberry branches and leaves (mixture) and avocado seed was evaluated. This plant material is part of agro-industrial waste from the production process of the company Camposol S.A. To determine the concentration of polyphenols, the Folin Ciocalteu method was used and for the antioxidant capacity, the DPPH radical method. The tentative identification of compounds present in each extract was performed using UHPLC-DAD-ESI/MS. The acetone extracts were dried and re-suspended in water. Three concentrations (5, 25 and 50 mg/mL) were used on the inhibition of spore germination and mycelial growth of Botrytis sp. 55% inhibition of spores was obtained after 24 h of incubation and 19% inhibition in growth mycelial at 7 days of incubation. This research contributes to the valorization of by-products, giving them added value, encouraging the development and implementation of new products based on plant material with important bioactive potential for the emerging sector of Agro-industry.

The design, synthesis, and inhibition of Clostridioides difficile spore germination by acyclic and bicyclic tertiary amide analogs of cholate

Clostridioides difficile infection (CDI) is a major identifiable cause of antibiotic-associated diarrhea. In our previous study (J. Med. Chem., 2018, 61, 6759–6778), we have identified N-phenyl-cholan-24-amide as a potent inhibitor of spore germination. The most potent compounds in our previous work are N-arylamides. We were interested in the role that the conformation of the amide plays in activity. Previous research has shown that secondary N-arylamides exist exclusively in the coplanar trans conformation while tertiary N-methyl-N-arylamides exist in a non-planar, cis conformation. The N-methyl-N-phenyl-cholan-24-amide was 17-fold less active compared to the parent compounds suggesting the importance of the orientation of the phenyl ring. To lock the phenyl ring into a trans conformation, cyclic tertiary amides were prepared. Indoline and quinoline cholan-24-amides were both inhibitors of spore germination; however, the indoline analogs were most potent. Isoindoline and isoquinoline amides were inactive. We found that the simple indoline derivative gave an IC50 value of 1 μM, while the 5′-fluoro-substituted compound (5d) possessed an IC50 of 400 nM. To our knowledge, 5d is the most potent known spore germination inhibitor described to date. Taken together, our results indicate that the trans, coplanar conformation of the phenyl ring is required for potent inhibition.

Antifungal activity of Terminalia chebula extract against wilt fungi Fusariumoxysporum an important plant pathogen

Terminalia chebula, a deciduous plant, endogenous to India has medicinal value. Its fruits are known for its cure to many ailments in human beings. This study is to test the Biological activity of these compounds tested against plant pathogenic fungai Fusarium oxysporum which cause wilt in economically important crops. Wilt is a devastating disease whichdestroys the infected plant and cause economic loss to farmers. Panama disease in bananas is a type of wilt disease which is very prevalent in India. This fungai has broad host range from tomato, cotton etc. Outbreak reported in many parts of India. Standard culture of Fusarium oxysporum ITCC -6246, Fusarium oxysporum f. sp. ciceri ITCC 3636 and Fusarium oxysporum f. sp. Lycopersici MTCC 10270 were used to detect the potential chemical compound in dried fruitby macro-dilution.Each organic solvent (Water, Ethanol, Chloroform, Benzene) has different extraction capacity based on the polarity of chemical compound in plants. These chemical compounds extensively studied for their antioxidant property and preliminary screening of chemical compound constituents in all extract. Mycelium growth inhibition tested on solid medium and inhibition measured in mm diameter. Spores of Fusarium sp. present in soil for many months in dormant form. Under suitable climatic conditions this will germinate and cause infection in plants. Rate of spore germination inhibition in liquid medium measured and calculated for every solvent extract. Rate of inhibition was calculated and analysed statistically by t test. The efficient solvent extract determined for bulk extraction of biologically active compound from seeds.

Antifungal activity of Terminalia chebula extract against wilt fungi Fusarium oxysporum an important plant pathogen

Terminalia chebula, a deciduous plant, endogenous to India has medicinal value. Its fruits are known for its cure to many ailments in human beings. This study is to test the biological activity of these compounds tested against plant pathogenic fungi Fusarium oxysporum which cause wilt in economically important crops. Wilt is a devastating disease which destroys the infected plant and cause economic loss to farmers. Panama disease in bananas is a type of wilt disease which is very prevalent in India. This fungi has broad host range from tomato, cotton etc. Outbreak reported in many parts of India. Standard culture of Fusarium oxysporum ITCC -6246, Fusarium oxysporum f. sp. ciceri ITCC 3636 and Fusarium oxysporum f. sp. lycopersici MTCC 10270 were used to detect the potential chemical compound in dried fruit by macro-dilution. Each organic solvent (Water, Ethanol, Chloroform, Benzene) has different extraction capacity based on the polarity of chemical compound in plants. These chemical compounds extensively studied for their antioxidant property and preliminary screening of chemical compound constituents in all extract. Mycelium growth inhibition tested on solid medium and zone of inhibition measured in mm diameter. Spores of Fusarium sp. present in soil for many months in dormant form. Under suitable climatic conditions this will germinate and cause infection in plants. Rate of spore germination inhibition in liquid medium measured and calculated for every solvent extract. Rate of inhibition was calculated and analysed statistically by t test. The efficient solvent extract determined for bulk extraction of biologically active compound from seeds.

Biocontrol of cucumber Fusarium wilt by Trichoderma asperellum FJ035 dependent on antagonism and spatiotemporal competition with Fusarium oxysporum

Fusarium wilt is one of the major constraints of cucumber production worldwide and is difficult to control in production. This study selected a strain of Trichoderma asperellum FJ035 with a good antagonistic effect against Fusarium oxysporum f. sp. cucumerinum Owen (FOC) by plate confrontation test and secondary metabolites (volatile substances and non-volatile substances) antagonism tests. T. asperellum FJ035 inhibited spore germination of FOC and improved the germination potential of cucumber seeds. The spatiotemporal competition dynamics of T. sperellum FJ035 green fluorescence-labeled strain and FOC red fluorescence-labeled strain in the cucumber rhizosphere were monitored under a laser confocal microscope. The results showed that the vitality of FOC in the cucumber rhizosphere exceeded that of T. asperellum FJ035, but T. asperellum FJ035 exerted some inhibitory effects on FOC. When inoculation of T. asperellum FJ035 24 h before inoculation of FOC could significantly reduce the accumulation of FOC on the roots of cucumber, corresponding to the highest control efficiency against cucumber Fusarium wilt were 69.79% and 75.96% under hydroponic and potted conditions, respectively. T. asperellum FJ035 also significantly improved the root length, plant height, stem thickness, fresh weight, and area index of the first true leaves of cucumber seedlings, and effectively mitigating the adverse effects of FOC on cucumber growth.

Senkyunolide B exhibits broad-spectrum antifungal activity against plant and human pathogenic fungi via inhibiting spore germination and destroying the mature biofilm.

Aspergillus infection seriously jeopardize the health and safety of life of immunocompromised patients. The emergences of antifungal resistance highlight a demand to find new effective antifungal drugs. Angelica sinensis is a medicine-food herb and phthalides are its characteristic components. A few of phthalides have been reported to display satisfactory antifungal activities against plant pathogenic fungi. However, the structure activity relationships and antifungal action mechanism of phthalides remain to be further explored and elucidated. The antifungal activities of five natural phthalides and four artificial analogues were investigated, and their structure activity relationships were preliminarily elucidated in current study. The benzene ring moiety played an essential role in their antifungal activities; the oxygen-containing substituents on the benzene ring obviously impact their activities, the free hydroxyl was favorable to the activity. Typical phthalide senkyunolide B (SENB) exhibited broad antifungal activities against human and plant pathogenic fungi, especially, Aspergillus fumigatus. SENB affected the spore germination and hyphae growth of A. fumigatus via downregulating phosphatidylinositol-PKC-calcineurin axis and the expression of ENG genes. Moreover, SENB disturbed the oxidation-reduction process in A. fumigatus to destroy the mature biofilms. In vivo experiments indicated SENB significantly prolonged survival and decreased fungal burden in mouse model of invasive pulmonary aspergillosis. Phthalides could be considered as the valuable leads for the development of antifungal drug to cure plant and human disease. This article is protected by copyright. All rights reserved.

Two novel antimicrobial peptides against vegetative cells, spores and biofilm of Bacillus cereus

Bacillus cereus is a ubiquitous bacterium that causes food-associated gastrointestinal diseases. The ability to form spores and biofilm makes this bacterium highly resistant to antimicrobial agents and food preservatives, posing persistent risks to consumers and the food industry. The excessive use of antibiotics and chemical preservatives has led to the emergence of resistant B. cereus strains, impacting the safety of food. Therefore, there is demand for new antimicrobial agents to combat B. cereus. The use of antimicrobial peptides (AMPs) for food preservation has attracted attention because they can preserve food quality with low possibility of bacteria acquiring resistance. In this research, a series of peptide derivatives based on the previously reported peptide D51 (sequence FLFRVASKVFPALIGKFKKK) was designed and synthesized. Two of the peptides, D51-P11G and D51-P11K, exhibited satisfactory antimicrobial (MICs: 8 μg/mL) activities toward B. cereus, including diarrheal and emetic reference strains. Peptides D51-P11G and D51-P11K showed good physiological stability, high safety and a low tendency to induce bacterial resistance. Meanwhile, at 16 μg/mL, D51-P11G and D51-P11K could inhibit spore germination and biofilm formation. Studies of the antibacterial mechanism suggested that D51-P11G and D51-P11K exert their antibacterial activities mainly via a membrane-lytic mechanism, but they also bound to genome DNA of the bacteria. Notably, D51-P11G and D51-P11K (32 μg/mL) could control the growth of B. cereus in boiled rice and minced meat, the antimicrobial activities were almost the same as or even better than nisin A (300 μg/mL). These findings suggest that D51-P11G and D51-P11K are ideal candidates for application against vegetative cells, spores, and biofilm of B. cereus.

Antifungal effect of cinnamic acid and induced resistance of cinnamic acid-protocatechuic acid-CaCl2-NaCl-pullulan composite preservative to Trichoderma harzianum in postharvest Hypsizygus marmoreus

Hypsizygus marmoreus (H. marmoreus) spoilage caused by Trichoderma harzianum (T. harzianum) results in significant financial losses, and the natural preservatives are being sought after to replace synthetic preservatives. To determine the antifungal activity of cinnamic acid (CA) against T. harzianum and clarify the induced disease resistance mechanism of H. marmoreus to T. harzianum, the CA (0.113 mg mL−1)-protocatechuic acid (0.121 mg mL−1)-CaCl2 (0.83%)-NaCl (0.65%)-pullulan (0.35%) composite preservative (CACP) at the spray rate of 13:1 was used to coating on H. marmoreus and storage at 4 ± 1 °C. Results showed that the inhibition rate (CA 3.00 mg mL−1), EC50 of mycelium growth and spore germination inhibition rate of CA to T. harzianum were 82.10%, 2.641 mg mL−1 and 0.128 mg mL−1, respectively. CACP treatment significantly reduced the rot rate and incidence of H. marmoreus. High levels of phenylalamine ammonia-lyase, peroxidase, polyphenol oxidase, ascorbate peroxidase, free proline, chitinase and β-1,3-glucanase in H. marmoreus treated with CACP significantly enhanced resistance to T. harzianum. Further, CACP treatment decreased the content of relative electrical conductivity and lessened the accumulation of malondialdehyde. Thus, the CACP may be used as an alternative bio-fungicide to control the severe disease caused by T. harzianum in H. marmoreus after harvest.

Carboxymethyl chitosan-quercetin conjugate: A sustainable one-step synthesis and use for food preservation

Bioactive polysaccharide, carboxymethyl chitosan-quercetin (CMCS-q) was prepared by a one-step reaction utilizing Schiff base chemistry. Notably, the presented conjugation method involves neither radical reactions nor auxiliary coupling agents. Physicochemical properties and bioactivity of the modified polymer were studied and compared to those of the pristine carboxymethyl chitosan, CMCS. The modified CMCS-q demonstrated antioxidant activity by TEAC assay and antifungal activity by inhibiting spore germination of plant pathogen Botrytis cynerea. Then, CMCS-q was applied as an active coating on fresh-cut apples. The treatment resulted in enhanced firmness, inhibited browning and improved microbiological quality of the food product.The presented conjugation method allows retaining antimicrobial and antioxidant activity of quercetin moiety in the modified biopolymer. This method can be further used as a platform for binding ketone/aldehyde-containing polyphenols and other natural compounds to form various bioactive polymers.