Cell-free Filtrates Research Articles

The potential biological activities of Aspergillus luchuensis-aided green synthesis of silver nanoparticles.

Biosynthetic metals have attracted global attention because of their safety, affordability, and environmental friendliness. As a consequence, the cell-free filtrate (CFF) of Dill leaf-derived endophytic fungus Aspergillus luchuensis was employed for the extracellularly synthesis silver nanoparticles (AgNPs). A reddish-brown color shift confirmed that AgNPs were successfully produced. The obtained AgNPs were characterized by UV-Vis (ultraviolet-visible spectroscopy), Transmission electron microscopy (TEM), FTIR, EDX, and zeta potential. Results demonstrated the creation of crystalline AgNPs with a spherical shape at 427.81 nm in the UV-Vis spectrum, and size ranged from 16 to 18 nm as observed by TEM. Additionally, the biogenic AgNPs had a promising antibacterial activity versus multidrug-resistant bacteria, notably, S. aureus, E. coli, and S. typhi. The highest growth reduction was recorded in the case of E. coli. Furthermore, the biosynthesized AgNPs demonstrated potent antifungal potential versus a variety of harmful fungi. The maximum growth inhibition was evaluated from A. brasinsilles, followed by C. albicans as compared to cell-free extract and AgNO3. In addition, data revealed that AgNPs possess powerful antioxidant activity, and their ability to scavenge radicals increased from 33.0 to 85.1% with an increment in their concentration from 3.9 to 1,000 μg/mL. Furthermore, data showed that AgNPs displayed high catalytic activity of safranin under light irradiation. The maximum decolorization percentage (100%) was observed after 6 h. Besides, the biosynthesized AgNPs showed high insecticidal potential against 3rd larval instar of Culex pipiens. Taken together, data suggested that endophytic fungus, A. luchuensis, is an attractive candidate as an environmentally sustainable and friendly fungal nanofactory.

Biodegradation and antimicrobial capability-induced heavy metal resistance of the marine-derived actinomycetes Nocardia harenae JJB5 and Amycolatopsis marina JJB11.

Currently, heavy metal-resistant (HMR) marine actinomycetes have attracted much attention worldwide due to their unique capabilities. In this study, 27 marine-derived actinomycetes were isolated from coastal beaches in the Arabian Gulf of Al-Jubail in Saudi Arabia and screened for resistance to 100 mg/L of the heavy metals Cd2+, Cr6+, Cu2+, Fe2+, Pb2+, and Ni2+ using different assay techniques. Six isolates were selected as HMRs, of which two isolates, JJB5 and JJB11, exhibited the highest maximum tolerance concentrations (200- > 300 mg/L). Both isolates were the highest among six-HMR screened for their biodegradation potential of plastics low-density polyethylene, polystyrene, and polyvinyl chloride, recording the highest weight loss (15 ± 1.22 - 65 ± 1.2%) in their thin films. They also showed the highest biodegradability of the pesticides acetamiprid, chlordane, hexachlorocyclohexane, indoxacarb and lindane, indicating promising removal capacities (95.70-100%) for acetamiprid and indoxacarb using HPLC analysis. Additionally, the cell-free filtrate (CFF) of both isolates displayed the highest antimicrobial activity among the six-HMR screened against a variety of microbial test strains, recording the highest inhibition zone diameters (13.76 ± 0.66 - 26.0 ± 1.13 mm). GC‒MS analyses of the ethyl acetate extract of their CFFs revealed the presence of diverse chemical compounds with a multitude of remarkable biological activities. Based on their spore morphology and wall-chemotype, they were assigned to the nocardioform-actinomycetes. Furthermore, their phenotypic characteristics, together with 16S rRNA gene sequencing (OR121525-OR121526), revealed them as Nocardia harenae JJB5 and Amycolatopsis marina JJB11. Our results suggest that marine HMR actinomycetes are promising candidates for various biotechnological applications.

Algicidal activity synchronized with nitrogen removal by actinomycetes: Algicidal mechanism, stress response of algal cells, denitrification performance, and indigenous bacterial community co-occurrence

The harmful algal blooms (HABs) can damage the ecological equilibrium of aquatic ecosystems and threaten human health. The bio-degradation of algal by algicidal bacteria is an environmentally friendly and economical approach to control HABs. This study applied an aerobic denitrification synchronization algicidal strain Streptomyces sp. LJH-12–1 (L1) to control HABs. The cell-free filtrate of the strain L1 showed a great algolytic effect on bloom-forming cyanobacterium, Microcystis aeruginosa (M. aeruginosa). The optimal algicidal property of strain L1 was indirect light-dependent algicidal with an algicidal rate of 85.0%. The functional metabolism, light-trapping, light-transfer efficiency, the content of pigments, and inhibition of photosynthesis of M. aeruginosa decreased after the addition of the supernatant of the strain L1 due to oxidative stress. Moreover, 96.05% nitrate removal rate synchronized with algicidal activity was achieved with the strain L1. The relative abundance of N cycling functional genes significantly increased during the strain L1 effect on M. aeruginosa. The algicidal efficiency of the strain L1 in the raw water was 76.70% with nitrate removal efficiency of 81.4%. Overall, this study provides a novel route to apply bacterial strain with the property of denitrification coupled with algicidal activity in treating micro-polluted water bodies.

Herbicidal proteins from Bacillus wiedmannii isolate ZT selectively inhibit ryegrass (Lolium temulentum L.).

The widespread use of chemical herbicides and the growing issue of weed resistance pose significant challenges in agriculture. To address these problems, there is a pressing need to develop biological herbicides based on bacterial metabolites. In this study, we investigated the impact of the cell-free culture filtrate (CFCF) from the ZT isolate, a bacilliform bacterium obtained from diseased wheat seeds, on the germination and seedling growth of various plant species, including wild oat, ryegrass, redroot, wheat, and chickpea. The results revealed that CFCF had a detrimental effect on the fresh and dry weight of stems and roots in most of the studied plants, except chickpeas. The CFCF was further subjected to separation into aqueous and organic phases using chloroform, followed by the division of the aqueous phase into 13 fractions using an alumina column. Notably, both the aqueous phase (20%) and all 13 fractions (ranging from 50% to 83%) displayed the ability to reduce the root length of ryegrass, a monocotyledonous weed. Liquid chromatography-mass spectrometry (LC-MS) analysis identified that fractions 3 and 7, which were effective against ryegrass but not redroot, contained Cry family proteins, including Cry10 Aa, Cry4 Ba, and Cry4 Aa. Additionally, 16s rRNA gene sequencing revealed that the ZT isolate is closely related (98.27%) to Bacillus wiedmannii. Conclusively, metabolites from the ZT bacterium hold promise for monocotyledonous weed-targeted herbicides, providing a constructive strategy to confront agricultural issues tied to chemical herbicides and weed resistance. © 2024 Society of Chemical Industry.

Unveiling the silver lining: examining the effects of biogenic silver nanoparticles on the growth dynamics of in vitro olive shoots

The current study aimed to evaluate the effects of biogenic silver nanoparticles (AgNPs) on growth behavior and leaf anatomy of in vitro growing shoots of ‘Picual’ and ‘Dolce’ olive cultivars. Biosynthesis of AgNPs was carried out using the cell-free filtrate of Fusarium oxysporum. The dimension and shape of the synthesized AgNPs have been analyzed using spectroscopy and topography analysis tools, confirming that the biosynthesis of AgNPs is a crystalline nanostructure with an average particle size of 37 nm. The shoots of the selected olive cultivars were cultured on Rugini olive medium-supplemented AgNPs at 0, 10, 20, and 30mg L− 1. The effect of genotypes on shoot multiplication was significant, ‘Picual’ recorded higher values of shoot growth parameters compared with ‘Dolce’ cultivar. Adding AgNPs to the culture medium significantly affected the growth of in vitro olive shoots. AgNPs at 20 and 30mg L− 1 produced higher values of the number of shoots, shoot length, and leaf number of Picual cv. compared with the control treatments, but the higher AgNPs concentration harmed the growth parameters of Dolce cv. and recorded lower growth values compared with the lower concentration (10mg L− 1). AgNPs had a significant effect on leaf morphology and their anatomical structure. The current results showed that the stimulatory effect of AgNPs on shoot growth of in vitro olive shoots is highly dependent on plant genotype and nanoparticle concentration.

Microbial Interactions as a Sustainable Tool for Enhancing PGPR Antagonism against Phytopathogenic Fungi

Microbial interactions, which regulate the dynamics of eco- and agrosystems, can be harnessed to enhance antagonism against phytopathogenic fungi in agriculture. This study tests the hypothesis that plant growth-promoting rhizobacteria (PGPR) can also be potential biological control agents (BCAs). Antifungal activity assays against potentially phytopathogenic fungi were caried out using cultures and cell-free filtrates of nine PGPR strains previously isolated from agricultural soils. Cultures of Bacillus sp. BS36 inhibited the growth of Alternaria sp. AF12 and Fusarium sp. AF68 by 74 and 65%, respectively. Cell-free filtrates of the same strain also inhibited the growth of both fungi by 54 and 14%, respectively. Furthermore, the co-cultivation of Bacillus sp. BS36 with Pseudomonas sp. BS95 and the target fungi improved their antifungal activity. A subsequent metabolomic analysis using Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) identified fengycin- and surfactin-like lipopeptides (LPs) in the Bacillus sp. BS36 cell-free filtrates, which could explain their antifungal activity. The co-production of multiple families of LPs by Bacillus sp. BS36 is an interesting feature with potential practical applications. These results highlight the potential of the PGPR strain Bacillus sp. BS36 to work as a BCA and the need for more integrative approaches to develop biocontrol tools more accessible and adoptable by farmers.

Trichoderma cf. asperellum and plant-based titanium dioxide nanoparticles initiate morphological and biochemical modifications in Hordeum vulgare L. against Bipolaris sorokiniana

BackgroundSpot blotch is a serious foliar disease of barley (Hordeum vulgare L.) plants caused by Bipolaris sorokiniana, which is a hemibiotrophic ascomycete that has a global impact on productivity. Some Trichoderma spp. is a promising candidate as a biocontrol agent as well as a plant growth stimulant. Also, the application of nanomaterials in agriculture limits the use of harmful agrochemicals and helps improve the yield of different crops. The current study was carried out to evaluate the effectiveness of Trichoderma. cf. asperellum and the biosynthesized titanium dioxide nanoparticles (TiO2 NPs) to manage the spot blotch disease of barley caused by B. sorokiniana and to assess the plant’s innate defense response.ResultsAloe vera L. aqueous leaf extract was used to biosynthesize TiO2 NPs by reducing TiCl4 salt into TiO2 NPs and the biosynthesized NPs were detected using SEM and TEM. It was confirmed that the NPs are anatase-crystalline phases and exist in sizes ranging from 10 to 25 nm. The T. cf. asperellum fungus was detected using morphological traits and rDNA ITS analysis. This fungus showed strong antagonistic activity against B. sorokiniana (57.07%). Additionally, T. cf. asperellum cultures that were 5 days old demonstrated the best antagonistic activity against the pathogen in cell-free culture filtrate. Also, B. sorokiniana was unable to grow on PDA supplemented with 25 and 50 mg/L of TiO2 NPs, and the diameter of the inhibitory zone increased with increasing TiO2 NPs concentration. In an in vivo assay, barley plants treated with T. cf. asperellum or TiO2 NPs were used to evaluate their biocontrol efficiency against B. sorokiniana, in which T. cf. asperellum and TiO2 NPs enhanced the growth of the plant without displaying disease symptoms. Furthermore, the physiological and biochemical parameters of barley plants treated with T. cf. asperellum or TiO2 NPs in response to B. sorokiniana treatment were quantitively estimated. Hence, T. cf. asperellum and TiO2 NPs improve the plant’s tolerance and reduce the growth inhibitory effect of B. sorokiniana.ConclusionSubsequently, T. cf. asperellum and TiO2 NPs were able to protect barley plants against B. sorokiniana via enhancement of chlorophyll content, improvement of plant health, and induction of the barley innate defense system. The present work emphasizes the major contribution of T. cf. asperellum and the biosynthesized TiO2 NPs to the management of spot blotch disease in barley plants, and ultimately to the enhancement of barley plant quality and productivity.

Exploitation of mangliculous marine fungi, Amarenographium solium, for the green synthesis of silver nanoparticles and their activity against multiple drug-resistant bacteria

Abstract The green synthesis pathway for silver nanoparticles (AgNPs) used in bacterial treatment is regarded as crucial because of its cost-effectiveness, nontoxicity, and eco-friendliness. During the present work, the mangliculous marine fungi Amarenographium solium isolated from the Arabian Gulf Coast of Saudi Arabia were utilized for the synthesis of AgNP, through the bio-reduction of aqueous silver nitrate (AgNO3) solution. The success in AgNP synthesis was visually identified by the development of dark brown color in the cell-free filtrate and was further confirmed by ultraviolet–visible spectroscopy, which showed a peak at 425 nm. The AgNPs produced were further characterized using X-ray diffraction data analysis that proved the bioreduction of silver to 20 nm, and transmission electron microscopy revealed the formation of well-dispersed spherical nanoparticles with an average mean size of 12 nm. The optimization reaction parameters of temperature, pH, and metal salt concentration were carried out and resulted in a combination of 30°C, 7 and 1.5 mM, respectively, for rapid and maximum yield production. The antibacterial activity of the produced nanoparticles was evaluated using the two-fold microdilution method and showed a minimum inhibitory concentration of 9.375 μg/mL of AgNP against multiple drug-resistant bacterial strains.

Newly Isolated Trichoderma spp. Show Multifaceted Biocontrol Strategies to Inhibit Potato Late Blight Causal Agent Phytophthora infestans both In Vitro and In Planta

Potato growers worldwide have been at war for more than 150 years with an enemy whose lifecycle, genome size and architecture, infection rate, and economic impacts are the epitome of a plant pathogen. Phytophthora infestans is an oomycete that causes the notorious late blight infection in potato and tomato fields. This study explored the benefits of the multitalented plant symbiotic fungi Trichoderma spp. and their metabolites as potential biopesticides against P. infestans. Eleven strains of Trichoderma spp. were obtained from soil and tree barks and were identified using DNA sequence analysis of three molecular markers. The antagonistic potential of the strains against P. infestans was first evaluated in vitro. In dual-culture assays, P. infestans growth was significantly inhibited (53 to 95%) by different Trichoderma spp. through direct mycoparasitism, competition for space and nutrients, or antibiosis. The cell-free filtrates (CFFs) of different Trichoderma strains were obtained and characterized for anti- Phytophthora activities as well as biochemical stability. The obtained results indicated that Trichoderma CFFs were chemically stable and strongly decreased P. infestans’ mycelial growth and zoospore motility and viability. Similarly, in leaf-disk assays, Trichoderma CFFs showed significant protection against P. infestans infection. Ultraperformance liquid chromatography analysis revealed the presence of harzianic acid, iso-harzianic acid, and 6-pentyl-2H-pyran-2-one as major compounds in different Trichoderma CFFs. Furthermore, selected Trichoderma strains significantly protected potato plants against soil-mediated late blight infection. Finally, Trichoderma spp. showed high compatibility with a copper-based fungicide, especially at lower concentrations, suggesting that both protective agents could be combined in integrated pest management programs. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Fostering resistance in common bean: Synergistic defense activation by Bacillus subtilis HE18 and Pseudomonas fluorescens HE22 against Pythium root rot

Root rot of common bean caused by Pythium aphanidermatum is a serious disease that causes significant losses to the production and yield of this crop. This study aimed to biocontrol the root rot disease of common bean using Bacillus subtilis HE18 and Pseudomonas fluorescens HE22 as effective bioagents and promote the growth of this plant. Using the in vitro dual culture assay, B. subtilis HE18 and P. fluorescens HE22 inhibited the radial growth of the pathogenic P. aphanidermatum by 67.95 and 48.39%, respectively. Chemical analysis of the cell-free filtrates of both bioagents using GC/MS demonstrated the production of twenty and thirteen volatile compounds by B. subtilis HE18 and P. fluorescens HE22, respectively, which may account for their significant antifungal efficacy. In the greenhouse, the application of a combination of both bio-inoculants displayed lower severity of pre- and post-emergence damping off and high plant survival, recording 10.1, 6.7, and 83.3%, respectively. The expression of the defense-related genes JERF3, GLU, and PR1, was examined in the treated plants using qPCR, where the highest upregulation levels were recorded for the infected plants that were treated with the combined biocontrol agents. Treating of the infected common bean with a combination of B. subtilis HE18 and P. fluorescens HE22 increased the activity levels of POD and PPO antioxidant enzymes and enhanced the phenol content. Combined treating of the infected plants with both bioagents increased the TSS to 14.15 °Brix, compared with the infected, untreated plants (7.05 °Brix). The dual application of both bioagents expressed a significant increment in Chl. a and b pigments, enhanced the levels of carotenoids, and increased the total pigments. Treating of the infected and control plants with both bio-inoculants caused an appreciable increment in the shoot height, root length, and shoot and dry weights, respectively. Moreover, the same treatment increased the pod weights, pod length and width, and the number of seeds pod−1, in addition to the yield plant−1. Finally, we concluded that both bioagents acted synergistically against the fungal pathogen, as they targeted multiple sites in the fungal cell and promoted the growth parameters and yields of the treated common bean plants.

Staurosporine-producing Streptomyces sp. strain 11 × 1 cell-free culture filtrates control diseases caused by the oomycete plant pathogens Pythium myriotylum and Phytophthora sojae

ABSTRACT Oomycetes are devastating soil-borne plant pathogens, and cause numerous losses on diverse crops worldwide. In this study, our aim was to identify actinomycetes with antimicrobial activity towards oomycetes from the rhizosphere of soybean. Strong growth inhibition of P. myriotylum was found in dual culture with a strain called 11 × 1, and also from using the 11 × 1 cell-free culture filtrate and EtOAc extract. The P. myriotylum growth-inhibiting activity of the 11 × 1 culture filtrates was stable at high temperatures, and acidic and alkaline conditions. The 11 × 1 strain was identified as a Streptomyces strain with the highest 16S rDNA sequence identity to S. scabiei, and phylogenomic analysis also showed clustering with S. scabiei strains. Applying the 11 × 1 culture filtrates to ginger and soybean leaves inhibited the necrosis caused by P. myriotylum and P. sojae, respectively. Pot assay experiments showed a strong control effect of the 11 × 1 culture filtrate against P. myriotylum-caused soft-rot disease of ginger, and against P. sojae caused root-rot of soybean. Analysis of the biosynthetic gene clusters from the genome of 11 × 1 predicted the production of staurosporine, and staurosporine was subsequently identified from LC-MS analysis of the 11 × 1 extract. The concentrations of staurosporine quantified in the 11 × 1 extracts were in the range of the staurosporine minimum inhibitory concentrations for P. myriotylum, supporting the contribution of staurosporine to the biocontrol effect of 11 × 1. The use of 11 × 1 culture filtrate to control both ginger and soybean diseases could be beneficial in an intercropping system of ginger and the leguminous nitrogen-fixing soybean.

Carcinogenic effect of human tumor-derived cell-free filtrates in nude mice.

Cancer remains a worldwide cause of morbidity and mortality. Investigational research efforts have included the administration of tumor-derived extracts to healthy animals. Having previously demonstrated that the administration of non-transmissible, human cancer-derived homogenates induced malignant tumors in mice, here, we examined the consequences of administering 50 or 100µg of protein of crude homogenates from mammary carcinoma, pancreatic adenocarcinoma, and melanoma samples in 6 inoculations per week during 2months. The concurrent control mice received homogenates of healthy donor-skin cosmetic surgery fragments. Mammary carcinoma homogenate administration did not provoke the deterioration or mortality of the animals. Multiple foci of lung adenocarcinomas with a broad expression of malignity histomarkers coexisting with small cell-like carcinomas were found. Disseminated cells, positive to classic epithelial markers, were detected in lymphoid nodes. The administration of pancreatic tumor and melanoma homogenates progressively deteriorated animal health. Pancreatic tumor induced poorly differentiated lung adenocarcinomas and pancreatic islet hyperplasia. Melanoma affected lungs with solid pseudopapillary adenocarcinomas. Giant atypical hepatocytes were also observed. The kidney exhibited dispersed foci of neoplastic cells within a desmoplastic matrix. Nuclear overlapping with hyperchromatic nuclei, mitotic figures, and prominent nuclear atypia was identified in epidermal cells. None of these changes were ever detected in the control mice. Furthermore, the incubation of zebrafish embryos with breast tumor homogenates induced the expression of c-Myc and HER-2 as tumor markers, contrasting to embryos exposed to healthy tissue-derived material. This study confirms and extends our hypothesis that tumor homogenates contain and may act as vectors for "malignancy drivers," which ultimately implement a carcinogenesis process in otherwise healthy mice.

Lipopeptide culture filtrates from Bacillus spp. provide effective protection to wheat against the foliar pathogen Zymoseptoria tritici.

Biocontrol products based on microorganisms and natural substances are promising alternatives to chemical pesticides that could contribute to develop a more sustainable agriculture. Here, we investigated the potential of cell-free culture filtrates (CFCFs) from two strains of the Bacillus subtilis group to inhibit Zymoseptoria tritici, a major fungal pathogen of wheat. Foliar application of CFCFs from Bacillus velezensis GA1 and Bacillus sp. III1 on wheat seedlings in a greenhouse strongly reduced Z. tritici disease severity (>90%). In vitro bioassays showed that CFCFs completely inhibited the spore germination and fungal growth (100%). In planta cytological investigations revealed a significant impact of the treatments on both spore germination (∼40% inhibition) and fungal growth of Z. tritici (>80% inhibition). High Performance Liquid Chromatography (HPLC) analysis showed that the Bacillus strains displayed different lipopeptide profiles. The CFCF obtained from Bacillus GA1 contained 90mg l-1 of iturin A+surfactins+fengycins and the CFCF obtained from Bacillus sp. III1 contained 25mg l-1 of mojavensin A (iturin family) + surfactins+fengycins. Strains of the B. subtilis group producing different iturins could provide several CFCF-based solutions for the biocontrol of Z. tritici.

Isolation and Identification of Bacillus subtilis LY-1 and Its Antifungal and Growth-Promoting Effects.

Peanut root rot, caused by Fusarium spp., is a devastating fungal disease. As part of a program to obtain a biocontrol agent to control peanut root rot in the field, a bacterial strain LY-1 capable of inhibiting the growth of the fungus in vitro was isolated from rhizosphere soil samples collected from wild mint by agar disk dilution and dual-culture assay. Strain LY-1 was identified as Bacillus subtilis based on morphological characteristics, 16S rDNA, and gyrA sequence analyses. The bacterial suspension and cell-free culture filtrate of LY-1 could significantly inhibit the growth of Fusarium oxysporum, Fusarium proliferatum and Fusarium solani, but volatile organic compounds from the cultures had only a weak effect on mycelial growth. The percentage inhibition of 20% concentration of the cell-free culture filtrate of LY-1 on conidium production of each of the three Fusarium species was greater than 72.38%, and the percentage inhibition by the culture filtration on the germination of conidia of the three species was at least 62.37%. The production of extracellular enzyme activity by LY-1 was studied in functional assays, showing protease, cellulase, amylase, chitinase, and β-1,3-glucanase activity, while LY-1 contained a gene encoding iturin, an antifungal lipopeptide. In addition, under pot culture in a greenhouse, culture filtrate of LY-1 significantly promoted the growth of peanut, increasing the fresh and dry mass of the plant by 30.77% and 27.27%, respectively, in comparison with the no-filtrate control. The culture filtrate of LY-1 increased the resistance of peanut plants to F. oxysporum, with the biocontrol efficiency reaching 44.71%. In conclusion, B. subtilis LY-1, a plant-growth-promoting rhizobacterium, was able to protect peanuts from Fusarium spp. infection.

Microbial bioformulation: a microbial assisted biostimulating fertilization technique for sustainable agriculture.

Addressing the pressing issues of increased food demand, declining crop productivity under varying agroclimatic conditions, and the deteriorating soil health resulting from the overuse of agricultural chemicals, requires innovative and effective strategies for the present era. Microbial bioformulation technology is a revolutionary, and eco-friendly alternative to agrochemicals that paves the way for sustainable agriculture. This technology harnesses the power of potential microbial strains and their cell-free filtrate possessing specific properties, such as phosphorus, potassium, and zinc solubilization, nitrogen fixation, siderophore production, and pathogen protection. The application of microbial bioformulations offers several remarkable advantages, including its sustainable nature, plant probiotic properties, and long-term viability, positioning it as a promising technology for the future of agriculture. To maintain the survival and viability of microbial strains, diverse carrier materials are employed to provide essential nourishment and support. Various carrier materials with their unique pros and cons are available, and choosing the most appropriate one is a key consideration, as it substantially extends the shelf life of microbial cells and maintains the overall quality of the bioinoculants. An exemplary modern bioformulation technology involves immobilizing microbial cells and utilizing cell-free filters to preserve the efficacy of bioinoculants, showcasing cutting-edge progress in this field. Moreover, the effective delivery of bioformulations in agricultural fields is another critical aspect to improve their overall efficiency. Proper and suitable application of microbial formulations is essential to boost soil fertility, preserve the soil's microbial ecology, enhance soil nutrition, and support crop physiological and biochemical processes, leading to increased yields in a sustainable manner while reducing reliance on expensive and toxic agrochemicals. This manuscript centers on exploring microbial bioformulations and their carrier materials, providing insights into the selection criteria, the development process of bioformulations, precautions, and best practices for various agricultural lands. The potential of bioformulations in promoting plant growth and defense against pathogens and diseases, while addressing biosafety concerns, is also a focal point of this study.

Characteristics of isolated lactic acid bacilli bacteria from black glutinous rice (Oryza sativa L.) tapai and its antimicrobial activity in mung bean (Vigna radiata L.) milk

Tapai is a traditional Indonesian fermented food that contains various microorganisms, including lactic acid bacteria (LAB). These LAB are probiotic microorganisms that can confer health benefits for the host consuming them. In this study, four LAB isolates –TM1, TM2, TM3 and TM4 – were isolated from the tapai liquid. The four isolates could grow at 30–40°C, pH 2.5–5.0, and 0.25–2.0% of bile. Antimicrobial screening using the plug agar method against E. coli, P. aeruginosa, B. subtilis, K. rhizophila and S. aureus showed that the growth of all tested bacteria could be inhibited only by TM1 and TM2, with the index of antimicrobial activity being higher for the latter. Antibiosis assay of TM2 cell-free filtrate in MRSB using the cylinder diffusion method also showed a zone of inhibition against all bacterial tested. Molecular identification based on 16S rRNA sequences revealed that the TM2 isolate was closely related to Lactiplantibacillus plantarum. TM2 cell-free filtrate of fermented mung bean milk was also able to inhibit all bacteria tested. Using a scanning electron microscope, observations of E. coli and S. aureus as representative bacteria showed disintegration and hollow bends on the cell wall. According to these results, mung bean milk can be fermented using TM2 as a potential isolate for as a probiotic agent to ferment mung bean milk.

Bacillus velezensis K-9 as a Potential Biocontrol Agent for Managing Potato Scab.

Crop pathogen infections can lead to substantial economic losses, but biocontrol, an environmentally friendly approach, can be used to control infections. For the biological management of potato scab disease, we assessed the potential use of Bacillus velezensis as a biocontrol agent. B. velezensis K-9 inhibited up to 44.90% of the infection caused by Streptomyces scabies, the causative agent of potato scab. Treatment of the S. scabies-infected potato plants with B. velezensis K-9 resulted in a significant reduction in the depth of the disease lesions compared with the untreated infected potato plants. In a radish seedling test, the B. velezensis K-9 culture and cell-free filtrate significantly reduced (P < 0.05) potato scab disease symptoms, suggesting that the strain K-9 was able to reduce S. scabies pathogenesis on potatoes. In a field test, the disease and scab indexes for B. velezensis K-9 against potato scab were significantly different from the control. In 2021, the potato yield for the B. velezensis K-9-treated plants was 12.44% higher than that for the control plants. In 2022, the potato yield following B. velezensis K-9 treatment increased by 12.65% compared with the control. In conclusion, B. velezensis K-9 prevented potato scab and increased potato yield. Thus, B. velezensis K-9 substantially reduced the occurrence of potato scab and could be used as a potential biocontrol agent for the management of potato scab.

Extracellular biosynthesis and characterization of silver and zinc oxide nanoparticles using Pseudomonas aeruginosa and Escherichia coli

Abstract Background: The development of dependable and environmentally friendly nanomaterial resources is an essential aspect of recent nanotechnology research and application. Microorganisms have recently been investigated as a potential biofactor for the synthesis of many nanoparticles (NPs). Objectives: The aim of this article is to evaluate the extracellular biosynthesis capabilities of metallic NPs such as silver (Ag) and zinc oxide (ZnO) by screening common bacteria. Materials and Methods: Silver nitrate and zinc nitrate were used as a source of Ag and ZnO NPs, by means of Escherichia coli and Pseudomonas aeruginosa as potential candidates for the rapid synthesis of NPs. Ag and ZnO NPs were synthesized using a reduction of aqueous solutions with cell-free filtrates of bacteria. Characterization of synthesized NPs was conducted by UV–Vis spectroscopy. Results: Transmission electron microscopy (TEM) was used to examine the particle size of (Ag, ZnO) NPs. The maximum absorbance was around (425, 450 nm) for Ag and (300, 380 nm) for ZnO by E. coli and P. aeruginosa, respectively. We found that particle size of Ag NP obtained from P. aeruginosa was smaller than that of NP obtained from E. coli. The range of particle size was 24–32 nm with an average of 29.5 nm for Ag P. aeruginosa and was 25–37 nm with an average of 32 nm for Ag E. coli. The particle size range of ZnO of P. aeruginosa was 23–28 nm with an average of 25 nm and was 25–34 nm with an average of 29.7 nm for E. coli. Conclusion: E. coli and P. aeruginosa are good candidates for biosynthesis of NPs. As a result, obliged characteristics and green synthesis and the potential issue for various environmental and health-related applications may exist.

Dual extracellular mycofabrication of cobalt and zinc nano metal oxides mediated by mycelial-cell free filtrate of Aspergillus sojae: Characterization and assessment of antibacterial activity

Foodborne pathogenic bacteria cause a wide range of infectious diseases that pose a serious threat to human health worldwide with significant social and economic consequences. Nano metal oxides have attracted paramount attention owing to their remarkable antimicrobial potency. Microbial synthesis of metal oxide nanoparticles has gained prominence due to cost-effectiveness, biocompatibility, and environmental friendliness. This study reports extracellular mycosynthesis of two nano metal oxides mediated by Aspergillus sojae mycelial cell-free filtrate (MCFF). A. sojae MCFF was reacted with cobalt chloride hexahydrate and zinc nitrate hexahydrate for the preparation of Co3O4 NPs and ZnO NPs, respectively. After reacting with each metal salt, A. sojae MCFF changed from transparent to greyish-brown and white-milky suspensions, indicating the mycosynthesis of Co3O4 NPs and ZnO NPs, respectively. Physicochemical and morphological properties of the two nano metal oxides were determined using various characterization techniques, involving XRD, FTIR, EDX, DLS, zeta potential analysis, XPS, and electron microscopy. The two nano metal oxides exhibited antibacterial potency against three foodborne pathogens. Co3O4 NPs had zones of inhibition (ZOI) of 19.33 ± 0.58, 20.67 ± 0.58, and 22.67 ± 0.58 mm against Escherichia coli (ATCC 43889), Salmonella enterica Serovar Typhimurium (ATCC 43174), and Staphylococcus aureus (ATCC 12600), respectively. Whereas ZnO NPs had ZOI of 15.67 ± 0.58, 15.67 ± 0.58, and 14.33 ± 0.58 mm against the three foodborne pathogens, respectively. The intact morphological structures of the bacterial cells collapsed following exposure to A. sojae-mediated Co3O4 NPs and ZnO NPs, with some cells having irregular, twisted, and rough surfaces. The current study concluded that A. sojae mycelia acted as potential biological entity for the biosynthesis of Co3O4 NPs and ZnO NPs. A. sojae-derived Co3O4 NPs and ZnO NPs can be potential candidates for use as antimicrobial nano metal oxides in food and pharmaceutical industries.

Characterization of a Bacillus velezensis strain as a potential biocontrol agent against soft rot of eggplant fruits

Postharvest soft rot of eggplant fruits caused by Pectobacterium carotovorum is a bacterial disease with a high disease incidence and produces substantial economic losses. This study aimed to control postharvest soft rot of eggplant fruits by Bacillus velezensis and investigate the possible control mechanisms based on the effects of B. velezensis on P. carotovorum subsp. carotovorum (Pcc) and eggplant fruits, respectively. B. velezensis effectively controlled postharvest soft rot of eggplant fruits and directly inhibited Pcc growth in vitro. The volatile metabolites produced by B. velezensis showed no inhibition on Pcc. Whereas the cell-free filtrate of B. velezensis significantly inhibited the growth of Pcc in vitro and in vivo. Notably, methanol-soluble precipitates obtained from cell-free filtrate showed significant inhibition on Pcc, and the primary inhibitory substances were identified as surfactin isoforms. Besides, iturin and fengycin isoforms with much lower relative abundance were also detected in the methanol-soluble precipitates. Furthermore, B. velezensis enhanced the activities of reactive oxygen species (ROS) scavenging enzymes in eggplant fruits that alleviated ROS and oxidative damage; thereby, B. velezensis enhanced the fruits' disease resistance.