Effects of temperature and medium composition on inhibitory activities of gossypol-related compounds against aflatoxigenic fungi

Isolation and identification of the endophytic fungus J2-3 and its disease-preventive and growth-promoting effects on cucumber

There are many problems that result from the use of a large number of chemical pesticides to control plant diseases, including pathogenic bacteria resistance, environmental contamination, and human health effects. Recently, endophytic fungi have become a significant source of bioactive fungicide products and an invaluable resource for excavating microbial pesticides. In this study, endophytic fungi with biocontrol potential were isolated and screened from Mikania micrantha leaves, stems, and roots. Fifty endophytic fungi were isolated and their antagonistic activity was studied in vitro using the confrontation culture method. The J2-3 strains from stems exhibit broad-spectrum and high activity. The strain's biological characteristics were determined by various culture conditions, and it was identified as Fusarium proliferatum by both morphological and ITS sequence analysis. Biological characteristics of the J2-3 strain were also tested. The optimum temperature for mycelium growth and sporulation was 25 °C and 30 °C, respectively. For mycelium growth, starch was the optimum carbon source, and peptone was the optimum nitrogen source for sucrose, mycelium growth, and sporulation. Mycelium growth was killed by a temperature of 60 °C, and sporulation was killed by a temperature of 55 °C. The light aided mycelium growth, and the light alternated between light and dark cycles for sporulation. Further, pot experiments were conducted to determine the antagonistic and viable effects of highly antagonistic strains on cucumber. The spore suspension's final control efficacy on cucumber wilt disease was up to 62.79% and it also promoted cucumber growth significantly. The results show that the entophytic fungus J2-3 from M. micrantha can protect cucumbers from wilt disease and promote growth.

Illumina-Based Analysis Yields New Insights Into the Fungal Contamination Associated With the Processed Products of Crataegi Fructus

Crataegi Fructus, a medicinal and edible herb in China, has been considered a popular dietary supplement globally. It is used for the treatment of dyspepsia and chronic heart failure according to the Chinese Pharmacopoeia (2020). However, fungal contamination in Crataegi Fructus affects its quality and safety, thus preventing its global promotion. In this study, we comprehensively studied the fungal community in processed products of Crataegi Fructus by high-throughput sequencing. A total of 21 Crataegi Fructus samples were collected from five provinces in China, and the samples were divided into five groups based on collection areas, as well as into three groups based on processing methods. We then targeted the internal transcribed spacer 2 sequence through the Illumina Miseq PE300 platform to investigate fungal composition and diversity. Results showed that all 21 samples were detected with fungal contamination, and Ascomycota was dominant at the phylum level. In the groups based on collection areas, Dothideomycetes, Pleosporaceae, and Alternaria were dominant at the class, family, and genus levels, respectively. In the groups based on processing methods, Dothideomycetes, Aspergillaceae, and Alternaria were the most abundant at the class, family, and genus levels, respectively. Differences in fungal communities between various groups were also observed. Furthermore, a total of 115 species were identified, among which seven were potential toxigenic, namely, Trichothecium roseum, Alternaria tenuissima, Aspergillus carbonarius, Penicillium brevicompactum, Aspergillus fumigatus, Rhizopus microspores, and Pichia fermentans. In conclusion, this study reveals great fungal richness and diversity of Crataegi Fructus, providing references for the prevention and control of fungal contamination of Crataegi Fructus in practical production.

Description of Aspergillus flavus growth under the influence of different factors (water activity, incubation temperature, protein and fat concentration, pH, and cinnamon essential oil concentration) by kinetic, probability of growth, and time-to-detection models

A Box-Behnken design was used to determine the effect of protein concentration (0, 5, or 10g of casein/100g), fat (0, 3, or 6g of corn oil/100g), a_w (0.900, 0.945, or 0.990), pH (3.5, 5.0, or 6.5), concentration of cinnamon essential oil (CEO, 0, 200, or 400μL/kg) and incubation temperature (15, 25, or 35°C) on the growth of Aspergillus flavus during 50days of incubation. Mold response under the evaluated conditions was modeled by the modified Gompertz equation, logistic regression, and time-to-detection model. The obtained polynomial regression models allow the significant coefficients (p<0.05) for linear, quadratic and interaction effects for the Gompertz equation's parameters to be identified, which adequately described (R²>0.967) the studied mold responses. After 50days of incubation, every tested model system was classified according to the observed response as 1 (growth) or 0 (no growth), then a binary logistic regression was utilized to model A. flavus growth interface, allowing to predict the probability of mold growth under selected combinations of tested factors. The time-to-detection model was utilized to estimate the time at which A. flavus visible growth begins. Water activity, temperature, and CEO concentration were the most important factors affecting fungal growth. It was observed that there is a range of possible combinations that may induce growth, such that incubation conditions and the amount of essential oil necessary for fungal growth inhibition strongly depend on protein and fat concentrations as well as on the pH of studied model systems. The probabilistic model and the time-to-detection models constitute another option to determine appropriate storage/processing conditions and accurately predict the probability and/or the time at which A. flavus growth occurs.