Variations in Fungal Community and Diversity in Doushen With Different Flavors

Variations of the fungal microbiome in Corydalis Rhizoma with different collection areas, processing methods, and storage conditions

Corydalis Rhizoma (CR, Yanhusuo in Chinese) has been widely used as an analgesic in herbal medicine and functional food. Cases of fungal and mycotoxin contamination in CR have been reported. In this study, the composition and diversity of fungal microbiome in CR samples from four herbal markets and two processing methods were investigated by DNA metabarcoding. Variations of the fungal microbiome in CR during cold and conventional storage were monitored. Results showed that Aspergillus was the dominant genus and saprotroph was the dominant trophic mode. Six potential toxigenic fungi, namely, Aspergillus fumigatus, Aspergillus ostianus, Aspergillus terreus, Penicillium citrinum, Penicillium oxalicum, and Trichothecium roseum, were detected. Differences in fungal composition and diversity among various groups based on collection areas and processing methods were also observed. Moreover, the relative abundance of dominant genera in CR samples stored at different temperatures was significantly different and changed with storage time. This study is the first to reveal the influence of collection areas, processing methods, and storage conditions on the fungal microbiome in CR, which was expected to provide a basis for control strategies of fungal contamination in the industrial chain of CR.

Exposure of Cryptococcus neoformans to Seven Commonly Used Agricultural Azole Fungicides Induces Resistance to Fluconazole as Well as Cross-Resistance to Voriconazole, Posaconazole, Itraconazole and Isavuconazole

BACKGROUND

Cross-resistance to medical azoles by exposure to azole pesticides is well documented for Aspergillus family fungi but is poorly evaluated for other environmental pathogen fungi, particularly for yeasts belonging to the Cryptococcus neoformans/Cryptococcus gattii species complexes.

METHODS

One thousand C. neoformans yeast were exposed to various concentrations of seven different commonly used azole pesticides. Clones surviving exposure were picked randomly, and their minimal inhibitory concentrations (MICs) of fluconazole, voriconazole, posaconazole, itraconazole and isavuconazole were assessed.

RESULTS

Depending on the pesticide used for exposure, up to 13.3% of selected Cryptococcus colonies showed a phenotype of resistance to fluconazole, and among them, several showed cross-resistance to another or several other medical azoles. Molecular mechanisms involved in the resistance setups seem to be dependent on ERG11 and AFR1 gene overexpression.

CONCLUSION

Exposure to any of the seven azole pesticides tested is capable of increasing the MIC of fluconazole in C. neoformans, including up to the level of the fluconazole-resistant phenotype, as well as generating cross-resistance to other medical azoles in some cases.

Bacterial communities in home-made Doushen with and without chili pepper

Doushen is a traditional Chinese fermented soybean product prepared with sterilizated soybeans under open conditions. However, little is known on the bacterial community and their influence on the flavor of Doushen. In the present study, Doushen samples with and without chili pepper were collected to reveal the bacterial community and assess a correlation between bacterial community and VFCs in the two kinds of Doushen samples. We identified four phyla and 97 bacterial genera in the two kinds of Doushen samples. In addition, a total of 17 significantly different OTUs were detected by LEfSe (Line Discriminant Analysis (LDA) Effect Size). Results of Principal coordinates analysis (PCoA), unweighted pair-group method (UPGMA) and functional and phenotypes prediction showed that bacterial communities in the two kinds of Doushen were significantly different. Spearman correlation analysis showed that all the dominant genera, except Clostridium Sensu stricto 1, were significantly correlated with the characteristic VFCs. This study provides a theoretical basis for improving the flavour quality of traditional homemade Doushen.

Influence of Tissue Type on the Bacterial Diversity and Community in Pork Bacon

In current study, bacterial diversity and community in different tissues of pork bacon were determined using high-throughput sequencing. In total, six phyla and 111 bacterial genera were identified. Among them, three dominant genera (Staphylococcus, Acinetobacter, and Macrococcus) were shared by all bacon samples. The linear discriminant analysis showed that 24 bacterial taxa significantly differentiated between the tissues. Results of non-metric Multidimensional Scaling and redundancy analysis showed that physicochemical characteristics of the tissue prominently structured the bacterial communities. Network analysis also illustrated that tissue type was an important factor impacting the bacterial interactions in different types of tissue. The results of current study can add valuable insights to the traditional homemade pork bacon.

Tissue Type: A Crucial Factor Influencing the Fungal Diversity and Communities in Sichuan Pork Bacon

This study aimed to the variations of fungal diversity and community structure in different parts of traditional homemade Sichuan pork bacon. A total of seven phyla and 91 fungal genera were identified. Among them, Ascomycota and Basidiomycota were the first and second most abundant phyla in the bacon tissues. In addition, five dominant genera (Aspergillus, Candida, Debaryomyces, Malassezia, and Penicillium) were shared by all bacon tissues. The numbers of OTUs unique to individual groups were 14, 67, and 65 for the muscle tissue, the adipose tissue, and pork skin, respectively. Linear discriminant analysis showed that a total of 31 taxa significantly differed among the groups. Results of redundancy analysis indicated that fat content, protein content, aw, and pH of bacon tissue shaped the bacon fungal communities. Results of network analysis also indicated that tissue type was a crucial factor influencing the fungal interactions in different tissues. This study can lay a foundation for further isolation and identification of fungi in the product and provides a basis for further research of food health in homemade traditional pork bacon.

High-throughput sequencing-based analysis of fungal diversity and taste quality evaluation of Douchi, a traditional fermented food

Douchi, a popular traditional fermented soybean product, is mainly made by natural fermentation. However, its taste quality is affected by specific fungal communities which vary greatly according to fermentation conditions and production technologies used in different regions. Therefore, the taste quality of Douchi samples from different regions was digitally evaluated using electronic tongue technology. In addition, the fungal community structures and its association of them were also identified using high-throughput sequencing technology. Results showed that there were obvious differences in the taste quality of samples from different regions, while the tastes of different types of samples from the same region were similar. Sourness, umami, richness, and saltiness were the main reasons for regional differences in taste. Similarly, the results of high-throughput sequencing indicated that samples from different regions displayed important differences in dominant fungal genus, among which Debaryomyces, Fusarium, Pichia, Aspergillus, and Saccharomyces were the main dominant fungi. Debaryomyces and Trichosporon were conducive to the formation of taste qualities of Douchi, while Cladosporium and Candida have a negative impact on the taste quality of Douchi var correlation analysis. This study indicated the effects of dominant fungi on the formation of Douchi taste quality, allowing a deeper understanding of the role of microbial species in generating fermented soybean products in China. Our work provides theoretical support to guide the improvement of the industrial production process of Douchi.