Soft rot is a destructive disease that inflicts significant losses on agricultural production and the economy post-harvest. Biocontrol strategies based on antagonistic microorganisms have a broad application prospect to fight against plant pathogens. This study utilized fluorescence-activated droplet sorting (FADS) technology as an alternative to traditional plate culture methods to isolate microorganisms with antagonistic activity against the soft rot pathogen Erwinia carotovora Ecc15. Initially, the culture performance of the FADS platform was evaluated by analyzing bacterial diversity in droplet culture samples and agar plate culture samples, our data showed that droplet culture exhibited higher species richness and diversity than plate culture, and more than 95% of the OTUs in the droplet samples belonged to the rare biosphere. Additionally, we developed a GFP-Ecc15-based FADS screening system, which achieved an enrichment ratio of up to 148. Using this system, we successfully screened 32 antagonistic bacteria from rhizosphere soil sample of healthy konjac plants, and some may be novel microbial resources, including the genera Lelliottia, Buttiauxella and Leclercia. Notably, strain D-62 exhibited the strongest antibacterial ability against Ecc15, with an inhibition zone diameter of (20.86 ± 1.56) mm. In vivo experiments conducted on the corms of Amorphophallus konjac demonstrated that strain D-62 could effectively reduce the infection ability of Ecc15 to the corms, indicating that strain D-62 has the potential to be developed as a biocontrol agent. Our findings suggested that the FADS screening system showed a screening efficiency approximately 3 × 10³ times higher than plate screening system, while significantly reducing costs of infrastructure, labor and consumables, it provides theoretical guidance for the screening of other plant pathogen biocontrol bacteria.

The objective of this study was to improve the flavor of Rosa sterilis S D Shi juice without reducing its antioxidant activity. Lactobacillus plantarum BJ-1 and Lactobacillus brevis BJ-31, previously isolated and preserved from naturally fermented kimchi, were used to ferment R. sterilis S D Shi juice, and the antioxidant activity and organoleptic properties were measured and analyzed to produce R. sterilis S D Shi juice with no reduction in antioxidant activity but with improved flavor. The experimental results showed that L. plantarum BJ-1 and L. brevis BJ-31 significantly increased the content of total phenolics and flavonoids, the scavenging capacity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals by 43.11% and 40.70%, and the scavenging capacity of 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals by 40% and 40%, respectively. From the organoleptic point of view, the taste and aroma of the R. sterilis S D Shi juice fermented by different lactobacilli gradually improved, and the aromatic amino acids of the fermented BJ-1 juice exceeded those of the non-fermented juice, while the aromatic amino acids and bitter amino acids of the fermented BJ-3 juice exceeded those of the non-fermented juice. R. sterilis S D Shi juice was both higher than those of unfermented juice, indicating that fermentation is a good way to improve the taste and flavor of R. sterilis S D Shi juice. This indicates that there was a significant improvement in the taste and flavor of the R. sterilis S D Shi juice. In this research, adding BJ-1 and BJ-31 respectively to R. sterilis S D Shi juice for fermentation, which significantly improved the taste and flavor of the juice, and this research provides a theoretical basis for probiotic fermentation of R. sterilis S D Shi juice and development.

SPE-UHPLC-MS/MS was firstly used to evaluate the contamination of ochratoxin A (OTA) in Rasa roxburghii and firstly assessed the human exposure risk of OTA in Rasa roxburghii. A more suitable method for OTA extraction and purification of R. roxburghii was obtained, 25 mL of R. roxburghii juice was treated with enzymatic hydrolysis at a concentration of 0.06 mg/mL. The resulting mixture was filtered and concentrated to dry, then redissolved with 0.2 mL of methanol and diluted with 0.4 mL of ultra-pure water. The activated HLB column, which was added the sample solution,  was washed with 6 mL of ultra-pure water and then eluted with 6 mL of methanol to purify. The eluent was collected and dried by nitrogen at 40 ℃,  then redissolved in 1 mL of methanol and filtered for detection. The hazard quotient (HQ) values of all samples ranged from 0.077% to 35.792%, which were within the allowable limits for human consumption. But from the perspective of OTA contamination, we recommend the max stored time were 14 days at room temperature, 35 days at 4 ℃ and 63 days at -20 ℃ for R. roxburghii fruit, and 7 days for sealed storage and the same-day for open storage at room temperature, 14 days for sealed storage and 7 days for open storage at 4 ℃, and 63 days for sealed storage and 56 days for open storage at -20 ℃ for R. roxburghii juice. And all thirty samples randomly sampled from the market were OTA negative. The results of this study can lay a foundation for the formulation of OTA limit standards in fruits and juice in the future, and provide a reference for consumers to consume R. roxburghii more healthily.