基于培养和宏基因组评价西瓜的保存方式

目的 基于培养和宏基因组评价日常西瓜的保存方式。方法 以市售纯品8424西瓜为实验材料，利用洁净菜刀处理样本，部分样本表面覆盖保鲜膜，分别置于室温(26℃)与冰箱(4℃)中，放置时长选择2、7和24 h几个不同时间点，测定西瓜表面菌落总数，用无菌棉签收集西瓜表面微生物进行宏基因组测序，分析不同保存方式下西瓜表面的菌落总数和微生物物种组成。结果 不同保存方式的西瓜表面菌落总数测定结果表明，随着保存时间的延长，菌落总数增加，低温能够有效抑制菌落总数生长，覆盖保鲜膜的样本表面菌落总数在保存7 h后显著增加，切除西瓜表面1 cm能够显著降低菌落总数；宏基因组测序分析结果表明，切开的西瓜表面有条件致病菌检出，并且存在假单胞菌属(Pseudomonas)、微小杆菌属(Exiguobacterium)以及欧文氏菌属(Erwinia)等多种较常见腐败菌。结论 切开后西瓜尽快放入冰箱可延长保存时间，24 h内食用并在食用前切除表面1 cm可降低致病风险。

Evaluation of watermelon preservation methods based on culture method and metagenomic sequencing

Objective Evaluation of daily watermelon preservation methods based on culture method and metagenomic sequencing. Methods The commercially available pure 8424 watermelon was used as the experimental material. The samples were processed with a clean household knife. Some samples were covered with cling film on the surface. They were placed at room temperature (26℃) and in the refrigerator (4℃) for different durations of 2, 7, and 24 hours. The total number of colonies on the surface of the watermelon was measured. Sterile cotton swabs were used to collect surface microorganisms of the watermelon for metagenomic sequencing, and the total number of colonies and microbial species composition on the watermelon surface under different preservation methods were analyzed. Results The results of the total number of colonies on the watermelon surface under different preservation methods indicated that the colony count increased with the prolongation of storage time. Low temperature effectively inhibited the growth of microbial colonies. The total number of colonies on the surface of the samples covered with cling film significantly increased after 7 hours of storage, and removing 1 cm from the surface of the watermelon significantly reduced the colony count. The results of metagenomic sequencing analysis showed the presence of potentially pathogenic bacteria on the cut surface of the watermelon, including Pseudomonas, Exiguobacterium, and Erwinia, which are common spoilage bacteria. Conclusion Placing the cut watermelon in the refrigerator as soon as possible can prolong its storage time. Consuming the watermelon within 24 hours and removing 1 cm from the surface before consumption can reduce the risk of pathogenic contamination.