Mycobiota associated with strawberry fruits, their mycotoxin potential and pectinase activity

Molecular identification and pathogenicity of endophytic fungi from corn ears

Endophytic fungi are widely known as fungi that infect internal tissues of host plants for all or part of their life cycles, without causing visible symptoms of disease. The present study was carried out to identify and investigate the pathogenicity of endophytic fungi residing in husks, silks, and kernels of corn. Endophytic fungi were isolated from surface-sterilised silks, kernels, and husks of healthy corn plants and identified using sequencing of multiple markers comprising TEF-1α, β-tubulin, calmodulin, ITS, LSU, and ACT. A total of 56 isolates of endophytic fungi belonging to 17 species, namely Fusarium pseudocircinatum (n = 8), F. verticillioides (n = 2), F. andiyazi (n = 4), F. sacchari (n = 1), F. mangiferae (n = 1), F. fujikuroi (n = 1), F. proliferatum (n = 3), F. incarnatum (n = 2), Penicillium oxalicum (n = 2), P. polonicum (n = 2), P. citrinum (n = 11), Aspergillus flavus (n = 10), A. tubingensis (n = 1), Cladosporium tenuissimum (n = 3), Aureobasidium pullulans (n = 3), Curvularia lunata (n = 1), and Epicoccum sorghinum (n = 1) were identified. Pathogenicity test showed that all endophytic fungi induced varying severities of disease symptoms on corn plants such as leaf chlorosis and necrosis, stem malformation, wilt, and stunted growth with F. verticillioides being the most virulent. The study revealed that corn tissues harbour diverse genera of endophytic fungi that can infect corn plants and may cause harmful effects to the host plants.

Time-kill kinetic of nano-ZnO-loaded nanoliposomes against Aspergillus niger and Botrytis cinerea

In vitro antimicrobial activity of nano-ZnO-loaded nanoliposomes at different levels of lecithin:nano-ZnO ratio (5:1, 15:1, and 25:1 w/w) against Aspergillus niger (IBRC-M 30095) and Botrytis cinerea (IBRC-M 30162) was evaluated. Nanoliposome formulations containing nano-ZnO were fabricated through thin-layer hydration sonication and heat methods. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of nano-ZnO-loaded nanoliposomes and free nano-ZnO against Aspergillus niger and Botrytis cinerea were determined. The time-kill experiments were performed for each isolate. Results showed that the encapsulation of nano-ZnO in nanoliposome systems significantly enhanced their antimicrobial activities by improving the penetration of ZnO nanoparticles the fungi cell membrane. In vitro antifungal activity of nano-ZnO-loaded nanoliposomes against Aspergillus niger and Botrytis cinerea was increased in thin-layer hydration sonication method compared with the heat method. The log phase for Aspergillus niger and Botrytis cinerea was around 70 h. Adding nano-ZnO-loaded nanoliposomes to the culture medium shortened the log phase for both Aspergillus niger and Botrytis cinerea. The highest antimicrobial activity of nanoliposomes was achieved using nanoliposomes containing the lecithin:nano-ZnO ratio of 25:1 (w/w) as compared to all samples. However, the length of the log phase growth cultures exposed to the nanoliposome formulations prepared by thin-layer hydration sonication method with the lecithin:nano-ZnO ratio of 25:1 (w/w) at MIC and MFC values was 60 and 40 h for both Aspergillus niger and Botrytis cinerea, respectively.

Bacillus subtilis Edible Films for Strawberry Preservation: Antifungal Efficacy and Quality at Varied Temperatures

Fungal infestations, particularly from Rhizopus stolonifer, pose significant post-harvest challenges for strawberries, compromising their shelf life and quality. Traditional preservation methods, including refrigeration, offer limited protection against such pathogens. This study introduces an innovative approach, utilizing edible films infused with Bacillus subtilis strains GOS 01 B-67748 and HFC 103, known for their antifungal properties. We demonstrate that these bioactive films not only inhibit fungal growth effectively but also enhance the preservation of strawberries at varying temperatures. The inclusion of Bacillus subtilis in edible films represents a significant advancement in extending the viability of strawberries, surpassing the efficacy of conventional methods. Our findings suggest a promising avenue for natural, safe food preservation techniques, aligning with current consumer preferences for additive-free products. This research contributes to the broader understanding of microbial-based food preservation strategies, offering potential applications across a range of perishable commodities.

Identification and biodiversity patterns of Aspergillus species isolated from some soil invertebrates at high altitude using morphological characteristics and phylogenetic analyses

Background

The carcinogenic, mutagenic, and teratogenic chemicals such as aflatoxin are a worldwide health problem. Aspergillus spp., responsible for most cases of aflatoxin contamination, are common in the environment and spread easily to many different types of food. The objectives of this study were to conduct a survey of fungi associated with three soil invertebrates in Taif, Saudi Arabia, identify these isolates and explore mycotoxins formation.

Methods

In total, 114 fungal isolates were collected from various soil invertebrates (millipedes, Armadillidium vulgare and Porcellio laevis) in Taif, Saudi Arabia, among them, 22 isolates were identified as Aspergillus spp. based on morphological and molecular characteristics followed by both Fusarium and Penicillium.

Results

The sequences of ITS 1 and ITS 4 were utilized. Using bootstrap analysis, phylogenetic tree was split into two distinct clusters. Five sub clusters were included inside the first major cluster, and their bootstrap value was 99%. While, there were two small clusters in the second major cluster. All the tested Aspergillus strains were able to have a single PCR fragment amplified using the primer AspTef. TEF-1 DNA sequence bootstrap analysis with 1,000 replicates revealed two distinct groups. Additionally, the Aspergillus isolates were grouped into two different clusters with about 65% genetic similarity using ISSR-PCR analysis. The standard polymerase chain reaction was used to effectively amplify the Aopks, afl-A and omt-A genes in aflatoxigenic Aspergillus strains. Four Aspergillus strains used in this investigation were shown to generate aflatoxin B1. While, three Aspergillus stains showed ochratoxin genes.

Conclusions

In conclusion, the results indicate significant differences in the fungal community between ecoregions and soil invertebrates. Moreover, mycotoxin detection and identification among Aspergillus isolates were elucidated. This study could shed light on the risk of mycotoxin contamination along the supply chain.

Cyclo(L-Leucyl-L-Prolyl) from Lactobacillus coryniformis BCH-4 inhibits the proliferation of Aspergillus flavus: an in vitro to in silico approach

Fungal spoilage led to a considerable economic loss of foodstuff which ultimately affects public health due to mycotoxins production. Moreover, the consumption of commercial antifungal drugs creates side effects and develops antifungal resistance. To overcome these challenges, the current work was aimed to investigate novel antifungal cyclic dipeptide (CDP) from Lactobacillus coryniformis (Loigolactobacillus coryniformis) BCH-4. CDPs have flexible, cyclic, and stable conformation. The proline-based CDPs provide additional structural compatibility and bio-functional values. Keeping in view, high-performance liquid chromatography (HPLC) was performed to explore cyclo(L-Leu-L-Pro) from L. coryniformis BCH-4. The HPLC detected concentration (135 ± 7.07 mg/mL) exhibited in vitro antifungal activity of 5.66 ± 0.57 mm (inhibitory zone) against Aspergillus flavus. Based on these results, cyclo(L-Leu-L-Pro) was used as a bioprotectant for selected food samples (grapes, lemon, cashew nuts, and almonds). A significant impact of cyclo(L-Leu-L-Pro) was observed in contrast with MRS broth (control) and cell-free supernatant. In silico molecular docking analysis of this CDP was carried out against FAD glucose dehydrogenase, dihydrofolate reductase, and urate oxidase of A. flavus as target proteins. Among these proteins, FAD glucose dehydrogenase exerted strong interactions with cyclo(L-Leu-L-Pro) having S-score of  - 8.21. The results evaluated that the detected CDP has strong interactions with selected proteins, causing excellent growth inhibition of A. flavus. Therefore, cyclo(L-Leu-L-Pro) could be used as a potent bioprotectant against food-borne pathogenic fungi.

Nanoencapsulation-Based Edible Coating of Essential Oils as a Novel Green Strategy Against Fungal Spoilage, Mycotoxin Contamination, and Quality Deterioration of Stored Fruits: An Overview

Currently, applications of essential oils for protection of postharvest fruits against fungal infestation and mycotoxin contamination are of immense interest and research hot spot in view of their natural origin and possibly being an alternative to hazardous synthetic preservatives. However, the practical applications of essential oils in broad-scale industrial sectors have some limitations due to their volatility, less solubility, hydrophobic nature, and easy oxidation in environmental conditions. Implementation of nanotechnology for efficient incorporation of essential oils into polymeric matrices is an emerging and novel strategy to extend its applicability by controlled release and to overcome its major limitations. Moreover, different nano-engineered structures (nanoemulsion, suspension, colloidal dispersion, and nanoparticles) developed by applying a variety of nanoencapsulation processes improved essential oil efficacy along with targeted delivery, maintaining the characteristics of food ingredients. Nanoemulsion-based edible coating of essential oils in fruits poses an innovative green alternative against fungal infestation and mycotoxin contamination. Encapsulation-based coating of essential oils also improves antifungal, antimycotoxigenic, and antioxidant properties, a prerequisite for long-term enhancement of fruit shelf life. Furthermore, emulsion-based coating of essential oil is also efficient in the protection of physicochemical characteristics, viz., firmness, titrable acidity, pH, weight loss, respiration rate, and total phenolic contents, along with maintenance of organoleptic attributes and nutritional qualities of stored fruits. Based on this scenario, the present article deals with the advancement in nanoencapsulation-based edible coating of essential oil with efficient utilization as a novel safe green preservative and develops a green insight into sustainable protection of fruits against fungal- and mycotoxin-mediated quality deterioration.

Prevalence of lipase producer Aspergillus niger in nuts and anti-biofilm efficacy of its crude lipase against some human pathogenic bacteria

Nuts are the natural source of healthy lipids, proteins, and omega-3. They are susceptible to fungal and mycotoxins contamination because of their high nutritional value. Twenty-five species comprising 12 genera were isolated from 80 samples of dried fruits and nuts using the dilution plate method. Peanut recorded the highest level of contamination followed by coconut; almond and raisin were the lowest. Aspergillus was the most prevalent genus and A.niger, was the most dominant species. The morphological identification of the selected A.niger isolates as they were detected in high frequency of occurrence was confirmed by using 18SrRNA sequence. Ochratoxin biosynthesis gene Aopks was detected in the tested isolates. Lipase production by the selected A.niger isolates was determined with enzyme activity index (EAI) ranging from 2.02 to 3.28. A.niger-26 was the highest lipase producer with enzyme activity of 0.6 ± 0.1 U/ml by the trimetric method. Lip2 gene was also detected in the tested isolates. Finally, the antibacterial and antibiofilm efficiency of crude lipase against some human pathogens was monitored. Results exhibited great antibacterial efficacy with minimum bactericidal concentration (MBC) of 20 to 40 µl/100 µl against Escherichiacoli, Pseudomonasaeruginosa, Proteusmirabilis, and Methicillin-resistant Staphylococcusaureus (MRSA). Interestingly, significant anti-biofilm efficacy with inhibition percentages of 95.3, 74.9, 77.1 and 93.6% was observed against the tested pathogens, respectively.