Leaf-associated microbiota on perilla (Perilla frutescens var. frutescens) cultivated in South Korea to detect the potential risk of food poisoning

Comparative global profiling of Perilla leaf and stem via transcriptomics and metabolomics

Perilla (Perilla frutescens L.) is a time-honored herbal plant with widespread applications in both medicine and culinary practices around the world. Profiling the essential organs and tissues with medicinal significance on a global scale offers valuable insights for enhancing the yield of desirable compounds in Perilla and other medicinal plants. In the present study, genome-wide RNA-sequencing (RNA-seq) and assessing the global spectrum of metabolites were carried out in the two major organs/tissues of stem (PfST) and leaf (PfLE) in Perilla. The results showed a total of 18,490 transcripts as the DEGs (differentially expressed genes) and 144 metabolites as the DAMs (differentially accumulated metabolites) through the comparative profiling of PfST vs PfLE, and all the DEGs and DAMs exhibited tissue-specific trends. An association analysis between the transcriptomics and metabolomics revealed 14 significantly enriched pathways for both DEGs and DAMs, among which the pathways of Glycine, serine and threonine metabolism (ko00260), Glyoxylate and dicarboxylate metabolism (ko00630), and Glucagon signaling pathway (ko04922) involved relatively more DEGs and DAMs. The results of qRT-PCR assays of 18 selected DEGs confirmed the distinct tissue-specific characteristics of all identified DEGs between PfST and PfLE. Notably, all eight genes associated with the flavonoid biosynthesis/metabolism pathways exhibited significantly elevated expression levels in PfLE compared to PfST. This observation suggests a heightened accumulation of metabolites related to flavonoids in Perilla leaves. The findings of this study offer a comprehensive overview of the organs and tissues in Perilla that have medicinal significance.

Characterization of the Bacterial Communities in Cichorium intybus According to Cultivation and Storage Conditions

Chicory leaves (Cichorium intybus) are widely consumed due to their health benefits. They are mainly consumed raw or without adequate washing, which has led to an increase in food-borne illness. This study investigated the taxonomic composition and diversity of chicory leaves collected at different sampling times and sites. The potential pathogenic genera (Sphingomonas, Pseudomonas, Pantoea, Staphylococcus, Escherichia, and Bacillus) were identified on the chicory leaves. We also evaluated the effects of various storage conditions (enterohemorrhagic E. coli contamination, washing treatment, and temperature) on the chicory leaves' microbiota. These results provide an understanding of the microbiota in chicory and could be used to prevent food-borne illnesses.

Seasonal Changes in the Microbial Communities on Lettuce (Lactuca sativa L.) in Chungcheong-do, South Korea

Lettuce is one of the most consumed vegetables worldwide. However, it has potential risks associated with pathogenic bacterial contamination because it is usually consumed raw. In this study, we investigated the changes in the bacterial community on lettuce (Lactuca sativa L.) in Chungcheong-do, South Korea, and the prevalence of foodborne pathogens on lettuce in different seasons using 16S rRNA gene-based sequencing. Our data revealed that the Shannon diversity index showed the same tendency in term of the number of OTUs, with the index being greatest for summer samples in comparison to other seasons. Moreover, the microbial communities were significantly different between the four seasons. The relative abundance of Actinobacteriota varied according to the season. Family Micrococcaceae was most dominant in all samples except summer, and Rhizobiaceae was predominant in the microbiome of the summer sample. At the genus level, the relative abundance of Bacillus was greatest in spring samples, whereas Pseudomonas was greatest in winter samples. Potential pathogens, such as Staphylococcus and Clostridium, were detected with low relative abundance in all lettuce samples. We also performed metagenome shotgun sequencing analysis on the selected summer and winter samples, which were expected to be contaminated with foodborne pathogens, to support 16S rRNA gene-based sequencing dataset. Moreover, we could detect seasonal biomarkers and microbial association networks of microbiota on lettuce samples. Our results suggest that seasonal characteristics of lettuce microbial communities, which include diverse potential pathogens, can be used as basic data for food safety management to predict and prevent future outbreaks.

Microbiota Analysis and Microbiological Hazard Assessment in Chinese Chive (Allium tuberosum Rottler) Depending on Retail Types

Chinese chive (Allium tuberosum Rottler) has potential risks associated with pathogenic bacterial contamination as it is usually consumed raw. In this study, we investigated the microbiota of Chinese chives purchased from traditional markets and grocery stores in March (Spring) and June (Summer) 2017. Differences in bacterial diversity were observed, and the microbial composition varied across sampling times and sites. In June, potential pathogenic genera, such as Escherichia, Enterobacter, and Pantoea, accounted for a high proportion of the microbiota in samples purchased from the traditional market. A large number of pathogenic bacteria (Acinetobacter lwoffii, Bacillus cereus, Klebsiella pneumoniae, and Serratia marcescens) were detected in the June samples at a relatively high rate. In addition, the influence of the washing treatment on Chinese chive microbiota was analyzed. After storage at 26°C, the washing treatment accelerated the growth of enterohemorrhagic Escherichia coli (EHEC) because it caused dynamic shifts in Chinese chive indigenous microbiota. These results expand our knowledge of the microbiota in Chinese chives and provide data for the prediction and prevention of food-borne illnesses.

Preparative separation of seven polyphenols from Perillae Folium via pH-zone-refining counter-current chromatography combined with high-speed counter-current chromatography

Perillae Folium is a well-known traditional Chinese medicine, and it possesses anti-inflammatory, anti-oxidant, and hypolipidemic effects. The pharmacological properties of Perillae Folium are based on its main functional compositions, such as phenolic acids, flavonoids, and volatile oils. In this study, seven polyphenols, including three phenolic acids and four flavonoid glycosides, were successfully isolated from Perillae Folium by pH-zone-refining counter-current chromatography (pH-ZRCCC) combined with traditional high-speed counter-current chromatography (HSCCC). First, the crude sample was separated by pH-ZRCCC using a biphasic solvent system composed of pet ether-ethyl acetate-acetonitrile-water (1 : 3 : 1 : 5, v/v). The upper phase of the biphasic solvent system added trifluoroacetic acid (10 mM) as the stationary phase, and the lower phase added ammonia water (30 mM) as the mobile phase. In this separation, one compound, rosemary acid (I), with high purity and a mixture were obtained. The mixture was further separated using HSCCC with a ethyl acetate-n-butanol-water (4.8 : 0.2 : 5, v/v) solvent system to obtain apigenin-7-O-[β-d-glucuronopyranosyl (1→2)-O-β-d-glucuronopyranoside] (II), luteolin-7-O-β-d-glucuronide (III), 4-hydroxycinnamic acid (IV), scutellarin (V), caffeic acid (VI), and apigenin-7-O-β-d-glucuronide (VII). The purities of the obtained compounds were above 92.7%. The study demonstrated that the combination of pH-ZRCCC and HSCCC is an effective method for the preparation and separation of polyphenols, particularly the complex mixture of phenolic acids and flavonoids from natural products.